January 2015 - December 2015
Angeler, D.G., C.R. Allen, C. Barichievy, T. Eason, A.S. Garmestani, N.A.J. Graham, D. Granholm, L. Gunderson, M. Knutson, K.L. Nash, R.J. Nelson, M. Nystrom, T. Spanbauer, C.A. STOW, and S.M. Sundstrom. Management applications of discontinuity theory. Journal of Applied Ecology:11 pp. (DOI:10.1111/1365-2664.12494) (2015).
(1) Human impacts on the environment are multifaceted and can occur across distinct spatiotemporal scales. Ecological responses to environmental change are therefore difficult to predict, and entail large degrees of uncertainty. Such uncertainty requires robust tools for management to sustain ecosystem goods and services and maintain resilient ecosystems. (2) We propose an approach based on discontinuity theory that accounts for patterns and processes at distinct spatial and temporal scales, an inherent property of ecological systems. Discontinuity theory has not been applied in natural resource management and could therefore improve ecosystem management because it explicitly accounts for ecological complexity. (3) Synthesis and applications. We highlight the application of discontinuity approaches for meeting management goals. Specifically, discontinuity approaches have significant potential to measure and thus understand the resilience of ecosystems, to objectively identify critical scales of space and time in ecological systems at which human impact might be most severe, to provide warning indicators of regime change, to help predict and understand biological invasions and extinctions and to focus monitoring efforts. Discontinuity theory can complement current approaches, providing a broader paradigm for ecological management and conservation.
Allan, J.D., S.D.P. Smith, P.B. McIntyre, C.A. Joseph, C.E. Dickinson, A.L. Marino, R.G. Biel, J.C. Olson, P.J. Doran, E.S. RUTHERFORD, J.E. Adkins, and A.O. Adeyemo. Using cultural ecosystem services to inform restoration priorities in the Laurentian Great Lakes. Frontiers in Ecology and the Environment 13(8):418-424 (DOI:10.1890/140328) (2015).
Ecological restoration programs often attempt to maintain or enhance ecosystem services (ES), but fine-scale maps of multiple ES are rarely available to support prioritization among potential projects. Here we use agency reports, citizen science, and social media as data sources to quantify the spatial distribution of five recreational elements of cultural ES (CES) – sport fishing, recreational boating, birding, beach use, and park visitation – across North America’s Laurentian Great Lakes, where current restoration investments exceed US$1.5 billion. These recreational CES are widely yet unevenly distributed, and spatial correlations among all except park visitation indicate that many locations support multiple CES benefits. Collectively, these five service metrics correlate with tourism gross domestic product, indicating that local economies benefit from ecosystem conditions that support CES. However, locations of high recreational CES delivery are often severely affected by environmental stressors, suggesting that either ecosystem condition or human enjoyment of these recreational CES is resilient even to substantial levels of stress. Our analyses show that spatial assessments of recreational CES are an informative complement to ecosystem stress assessments for guiding large-scale restoration efforts.
ANDERSON, E.J., Bechle A. J., Wu, C.H., Schwab, D.J. Mann, G.E. and Lombardy, K.A. Reconstruction of a meteotsunami in Lake Erie on 27 May 2012: Roles of atmospheric conditions on hydrodynamic response in enclosed basins. Journal of Geophysical Research: Oceans (DOI:10.1002/2015JC010883) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150054.pdf
On 27 May 2012, atmospheric conditions gave rise to two convective systems that generated a series of waves in the meteotsunami band on Lake Erie. The resulting waves swept three swimmers a 0.5 mi offshore, inundated a marina, and may have led to a capsized boat along the southern shoreline. Analysis of radial velocities from a nearby radar tower in combination with coastal meteorological observation indicates that the convective systems produced a series of outflow bands that were the likely atmospheric cause of the meteotsunami. In order to explain the processes that led to meteotsunami generation, we model the hydrodynamic response to three meteorological forcing scenarios: (i) the reconstructed atmospheric disturbance from radar analysis, (ii) simulated conditions from a high-resolution weather model, and (iii) interpolated meteorological conditions from the NOAA Great Lakes Coastal Forecasting System. The results reveal that the convective systems generated a series of waves incident to the southern shore of the lake that reflected toward the northern shoreline and reflected again to the southern shore, resulting in spatial wave focusing and edge wave formation that combined to impact recreational users near Cleveland, OH. This study illustrates the effects of meteotsunami development in an enclosed basin, including wave reflection, focusing, and edge wave formation as well as temporal lags between the causative atmospheric conditions and arrival of dangerous wave conditions. As a result, the ability to detect these extreme storms and predict the hydrodynamic response is crucial to reducing risk and building resilient coastal communities.
BAI, X., H. HU, J. WANG, Y. Yu, E. Cassano, and J. Maslanik. Responses of surface heat flux, sea ice, and ocean dynamics in the Chukchi-Beaufort Sea to storm passages during winter 2006/2007: A numerical study. Deep Sea Research I 102:101-117 (DOI:10.1016/j.dsr.2015.04.008) (2015).
This study investigates storm impacts on sea ice, oceanic dynamics, and surface heat flux in the Chukchi–Beaufort Seas using a coupled ice–ocean model (CIOM). Two types of storms affect the study area: Arctic-born cyclones and north-moving Aleutian lows, which lead to strong westerly and easterly winds, respectively. Driven by 6-hourly forcing, the CIOM successfully reproduced the storm impacts. Simulated sea ice movements are comparable to the satellite observations. Storms usually result in fast-moving ice, which is faster than the speed of the surface water, and the gap between sea ice and surface water speed increases with wind speed. Storms can alter the pathways of the Pacific inflow water: with westerly winds, the Pacific inflow water goes no further than the latitude of Wrangel Island, while with easterly winds the Pacific inflow water can flow northward into the interior Arctic basin. Strong easterly winds associated with north-moving Aleutian lows reverse the Alaskan Coastal Current and the Bering Slope Current, and induce upwelling along the north Alaska coast. Westerly winds associated with Arctic-born cyclones act in an opposite way. During the storms, heat loss to the atmosphere is about twice that of normal conditions, which is mainly attributed to increases of the sensible and latent heat fluxes over the open water. Heat loss over ice was quite stable with some small fluctuations in response to the storms.
BAI, X., J. WANG, J. Austin, D.J. SCHWAB, R.A. ASSEL, A.H. CLITES, J.F. BRATTON, M.C. COLTON, J. Lenters, B.M. LOFGREN, T. Wohlleben, S. Helfrich, H.A. VANDERPLOEG, L. LUO, and G.A. LESHKEVICH. A record-breaking low ice cover over the Great Lakes during winter 2011/2012: Combined effects of a strong positive NAO and La Nina. Climate Dynamics 44(5-6):1187-1213 (DOI:10.1007/s00382-014-2225-2) (2015).
A record-breaking low ice cover occurred in the North American Great Lakes during winter 2011/2012, in conjunction with a strong positive Arctic Oscillation/ North Atlantic Oscillation (AO/NAO) and a La Nina event. Large-scale atmosphere circulation in the Pacific/ North America (PNA) region reflected a combined signal of La Nina and NAO. Surface heat flux analysis shows that sensible heat flux contributed most to the net surface heat flux anomaly. Surface air temperature is the dominant factor governing the interannual variability of Great Lakes ice cover. Neither La Nina nor NAO alone can be responsible for the extreme warmth; the typical midlatitude response to La Nina events is a negative PNA pattern, which does not have a significant impact on Great Lakes winter climate; the positive phase of NAO is usually associated with moderate warming. When the two occurred simultaneously, the combined effects of La Nina and NAO resulted in a negative East Pacific pattern with a negative center over Alaska/Western Canada, a positive center in the eastern North Pacific (north of Hawaii), and an enhanced positive center over the eastern and southern United States. The overall pattern prohibited the movement of the Arctic air mass into mid-latitudes and enhanced southerly flow and warm advection from the Gulf of Mexico over the eastern United States and Great Lakes region, leading to the record-breaking low ice cover. It is another climatic pattern that can induce extreme warming in the Great Lakes region in addition to strong El Nino events. A very similar event occurred in the winter of 1999/2000. This extreme warm winter and spring in 2012 had significant impacts on the physical environment, as well as counterintuitive effects on phytoplankton abundance.
Bootsma, H.A., M.D. ROWE, C.N. Brooks, and H.A. VANDERPLOEG. Commentary: The need for model development related to Cladophora and nutrient management in Lake Michigan. Journal of Great Lakes Research 41:9 pp. (DOI:10.1016/j.jglr.2015.03.023) (2015).
In the past 10 to 15 years, excessive growth of Cladophora and other attached algae in the nearshore regions of Lake Michigan has re-emerged as an important resource management issue. This paper considers the question, “What information is needed to predict the response of Cladophora production in Lake Michigan to management variables, such as nutrient loading, and to additional environmental variables that are outside of management control?” Focusing on Lake Michigan, while drawing on the broader literature, we review the current state of information regarding 1) models of Cladophora growth, 2) models that simulate the physical environment, 3) models that simulate nearshore and whole-lake nutrient dynamics, with a specific focus on the role of dreissenid mussels, and 4) monitoring of Cladophora abundance. We conclude that while substantial progress has been made, considerable additional research is required before reliable forecasts of Cladophora response to nutrient loads and other environmental variables are possible. By providing a detailed outline of this complex, multidisciplinary problem, we hope that this paper will aid in coordinating collaborative research efforts toward the development of useful predictive models.
BURTON, G.A. Losing sight of science in the regulatory push to ban microbeads from consumer products and industrial use. Integrated Environmental Assessment and Management 11(3):346-347 (DOI:10.1002/ieam.1645) (2015).
Here we go again. Last summer, the state of Illinois was the first to ban tiny plastic microbeads in cosmetics, such as face wash. State legislators claimed the ban was a necessary response to what researchers and environmental groups claim is a serious environmental threat and the US Environmental Protection Agency (USEPA) has labeled as $13 billion annually in damages to marine life. On March 4 of this year, Illinois Congressmen Upton and Pallone introduced House Bill 1321 “to prohibit the sale or distribution of cosmetics containing synthetic plastic microbeads.” Similar measures are now pending in 13 states and in the US Congress. New York’s Attorney General Schneiderman, supported by Senator Gillibrand and a host of environmental groups, has proposed legislation to ban microbeads in cosmetics citing a need to “restore and protect New York’s waters.” Similar legislative efforts are underway in the European Union. It is rare when science and politics are on the same page, and this latest example of the rush to regulate is no exception.
Cha, Y.K., and C.A. STOW. Mining web-based data to assess public response to environmental events. Environmental Pollution 198:97-99 (DOI:10.1016/j.envpol.2014.12.027) (2015).
We explore how the analysis of web-based data, such as Twitter and Google Trends, can be used to assess the social relevance of an environmental accident. The concept and methods are applied in the shutdown of drinking water supply at the city of Toledo, Ohio, USA. Toledo's notice, which persisted from August 1 to 4, 2014, is a high-profile event that directly influenced approximately half a million people and received wide recognition. The notice was given when excessive levels of microcystin, a byproduct of cyanobacteria blooms, were discovered at the drinking water treatment plant on Lake Erie. Twitter mining results illustrated an instant response to the Toledo incident, the associated collective knowledge, and public perception. The results from Google Trends, on the other hand, revealed how the Toledo event raised public attention on the associated environmental issue, harmful algal blooms, in a long-term context. Thus, when jointly applied, Twitter and Google Trend analysis results offer complementary perspectives. Web content aggregated through mining approaches provides a social standpoint, such as public perception and interest, and offers context for establishing and evaluating environmental management policies.
Choi, J., C.D. Troy, and N. HAWLEY. Shear dispersion from near-inertial internal Poincare waves in large lakes. Limnology and Oceanography 60:2222-2235 (DOI:10.1002/lno.10163) (2015).
In this work, we study mixed layer lateral dispersion that is enhanced by near-inertial internal Poincar_ewaves in the offshore region of a large stratified lake, Lake Michigan. We examine the hypothesis that thevertical shear created by near-inertial internal Poincar_e waves is not only an energy source for vertical mixingin the thermocline and mixed layer, but also enhances horizontal dispersion via an unsteady shear flow dispersionmechanism. Complex empirical orthogonal function analysis reveals that the dominant shear structure is observed to mirror the thermal structure, with the location of maximum shear gradually lowered asthe mixed layer deepens. This changing structure of shear and vertical mixing produces different characteristicsin shear flow dispersion between the early and later stratified periods. The estimated depth-averaged surfacelayer vertical turbulent diffusivity grows from 1025 m2s21 to 1023 m2s21 over the stratified period, and the associated lateral dispersion coefficients are estimated as 0.1–40 m2s21. The Poincar_e waves are found toenhance greatly lateral dispersion for times less than the inertial period following release. In contrast, subinertial shear is the dominant mechanism responsible for shear dispersion for times greater than the inertial period. A simple approximation of the dispersion coefficient for lateral dispersion is developed, which scales as the product of surface current velocity (or wind friction velocity) and mixed layer depth. The calculated dispersion coefficients agree well with Okubo’s diffusion diagram for times up to a week, which suggests that unsteady shear dispersion is a plausible mechanism to explain observed dispersion rates in the mixed layer for early times after release.
David, S.R., R.S. Kik, J.S. Diana, E.S. RUTHERFORD, and M.J. Wiley. Evidence of countergradient variation in growth of Spotted Gars from core and peripheral populations. Transactions of the American Fisheries Society 144(4):837-850 (DOI:10.1080/00028487.2015.1040523) (2015).
Peripheral populations occupy the edge of a species’ range and may exhibit adaptations to potentially “harsher” marginal environments compared with core populations. The peripheral population of Spotted Gar Lepisosteus oculatus in the Great Lakes basin represents the northern edge of the species’ range and is completely disjunct from the core Mississippi River basin population. Age-0 Spotted Gars from the peripheral population experience a growing season approximately half that of the core population but reach similar sizes by winter, suggesting potential for countergradient variation in growth, i.e. an evolutionary response to an environmental gradient such as latitude to compensate for the usual phenotypic effect of that gradient. In this study we used two common garden experiments to investigate potential countergradient variation in growth of young-of-year Spotted Gars from peripheral populations in comparison with those from core populations. Our first experiment showed that in a common environment under temperatures within the first growing season (22–24_C), Spotted Gars from the peripheral population had significantly higher growth rates than those from the core population. Final Spotted Gar weight–length ratio was also higher in the peripheral versus core population. In our second experiment, under three temperature treatments (16, 23, and 30_C), maximum growth occurred at the highest temperature, whereas growth ceased at the lowest temperature for both populations. These results suggest that important genetic and physiological differences could exist between the two population groups, consistent with countergradient variation. Our findings indicate that countergradient growth variation can occur even in relatively slowly evolving fishes, such as gars (family Lepisosteidae), and that protection of peripheral populations should be a key component of fish conservation planning.
DAVIS, T.W., G.S. Bullerjahn, T. Tuttle, R.M. McKay, and S.B. Watson. Effects of increasing nitrogen and phosphorus concentrations on phytoplankton community growth and toxicity during Planktothrix blooms in Sandusky Bay, Lake Erie. Environmental Science & Technology 49:7197-7207 (DOI:10.1021/acs.est.5b00799) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150039.pdf
Sandusky Bay experiences annual toxic cyanobacterial blooms dominated by Planktothrix agardhii / suspensa. To further understand the environmental drivers of these events, we evaluated changes in the growth response and toxicity of the Planktothrix -dominated blooms to nutrient amendments with orthophosphate (PO 4 ) and inorganic and organic forms of dissolved nitrogen (N; ammonium (NH 4 ), nitrate (NO 3 ) and urea) over the bloom season (June − October). We complemented these with a metagenomic analysis of the planktonic microbial community. Our results showed that bloom growth and microcystin (MC) concentrations responded more frequently to additions of dissolved N than PO 4, and that the dual addition of NH 4 +PO 4 and Urea + PO 4 yielded the highest MC concentrations in 54% of experiments. Metagenomic analysis confirmed that P. agardhii / suspensa was the primary MC producer. The phylogenetic distribution of nif H revealed that both heterocystous cyanobacteria and heterotrophic proteobacteria had the genetic potential for N 2 fixation in Sandusky Bay. These results suggest that as best management practices are developed for P reductions in Sandusky Bay, managers must be aware of the negative implications of not managing N loading into this system as N may significantly impact cyanobacterial bloom size and toxicity.
Fortin, D., D.S. Kaufman, M. Arnold, E. Schiefer, and N. HAWLEY. Late-summer peak in sediment accumulation in two lakes with contrasting watersheds. Geografiska Analler A. 97(4):709-719 (DOI:10.1111/geoa.12110) (2015).
The timing of clastic sedimentation in two glacial-fed lakes with contrasting watersheds was monitored using sequencing sediment traps for two consecutive years at Allison Lake (Chugach Range, Alaska) and four months at Shainin Lake (Brooks Range, Alaska). Shainin Lake is a weakly stratified lake fed by distant glaciers, whereas Allison Lake is more strongly stratified and fed predominantly by proximal glaciers. At Shainin Lake, sediment accumulation started in late June and reached its maximum in mid-August, just before lake mixing and during a period of low river discharge. The grain size of the sediment reaching the sediment trap in Shainin Lake was homogenous throughout the summer. At Allison Lake, pulsed sedimentation of coarse particles during late summer and early fall storms were superimposed on the fine-grained sedimentation pattern similar to that observed at Shainin Lake. These storms triggered underflows that were observed in the thermal structure of the lake and deposited abundant sediment. The sequencing sediment traps reveal a lag between fluvial discharge and sediment deposition at both lakes, implying limitations to interpreting intra-annual sedimentary features in terms of inflow discharge.
Fraker, M.E., E.J. ANDERSON, R.M. Brodnik, L. Carreon-Martinez, K.M. DeVanna, B.J. Fryer, D.D. Heath, J.M. Reichert, and S.A. Ludsin. Particle backtracking improves breeding subpopulation discrimination and natal-source identification in mixed populations. PLOS One 10(3):24 pp. (DOI:10.1371/journal.pone.0120752) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150014.pdf
We provide a novel method to improve the use of natural tagging approaches for subpopulation discrimination and source-origin identification in aquatic and terrestrial animals with a passive dispersive phase. Our method integrates observed site-referenced biological information on individuals in mixed populations with a particle-tracking model to retrace likely dispersal histories prior to capture (i.e., particle backtracking). To illustrate and test our approach, we focus on western Lake Erie’s yellow perch (Perca flavescens) population during 2006–2007, using microsatellite DNA and otolith microchemistry from larvae and juveniles as natural tags. Particle backtracking showed that not all larvae collected near a presumed hatching location may have originated there, owing to passive drift during the larval stage that was influenced by strong river- and wind-driven water circulation. Re-assigning larvae to their most probable hatching site (based on probabilistic dispersal trajectories from the particle backtracking model) improved the use of genetics and otolith microchemistry to discriminate among local breeding subpopulations. This enhancement, in turn, altered (and likely improved) the estimated contributions of each breeding subpopulation to the mixed population of juvenile recruits. Our findings indicate that particle backtracking can complement existing tools used to identify the origin of individuals in mixed populations, especially in flow-dominated systems.
Fraker, M.E., E.J. ANDERSON, C. May, K.-Y. Chen, J.J. Davis, K.M. DeVanna, M.R. DuFour, E.A. Marschall, C.M. Mayer, J.G. Miner, K.L. Pangle, J.J. Pritt, E.F. Roseman, J.T. Tyson, Y. Zhao, and S.A. Ludsin. Stock-specific advection of larval walleye (Sander vitreus) in western Lake Erie: Implications for larval growth, mixing, and stock discrimination. Journal of Great Lakes Research 41:16 (DOI:doi:10.1016/j.jglr.2015.04.008) (2015).
Physical processes can generate spatiotemporal heterogeneity in habitat quality for fish and also influence the overlap of pre-recruit individuals (e.g., larvae) with high-quality habitat through hydrodynamic advection. In turn, individuals from different stocks that are produced in different spawning locations or at different times may experience dissimilar habitat conditions, which can underlie within- and among-stock variability in larval growth and survival. While such physically-mediated variation has been shown to be important in driving intra- and inter-annual patterns in recruitment in marine ecosystems, its role in governing larval advection, growth, survival, and recruitment has received less attention in large lake ecosystems such as the Laurentian Great Lakes. Herein, we used a hydrodynamic model linked to a larval walleye (Sander vitreus) individual-based model to explore how the timing and location of larval walleye emergence from several spawning sites in western Lake Erie (Maumee, Sandusky, and Detroit rivers; Ohio reef complex) can influence advection pathways and mixing among these local spawning populations (stocks), and how spatiotemporal variation in thermal habitat can influence stock-specific larval growth. While basin-wide advection patterns were fairly similar during 2011 and 2012, smaller scale advection patterns and the degree of stock mixing varied both within and between years. Additionally, differences in larval growth were evident among stocks and among cohorts within stocks which were attributed to spatiotemporal differences in water temperature. Using these findings, we discuss the value of linked physical–biological models for understanding the recruitment process and addressing fisheries management problems in the world's Great Lakes.
GRONEWOLD, A.D., E.J. ANDERSON, B.M. LOFGREN, P.D. Blanken, J. WANG, J.P. SMITH, T.S. HUNTER, G.A. LANG, C.A. STOW, D. BELETSKY, and J.F. BRATTON. Impacts of extreme 2013-2014 winter conditions on Lake Michigan's fall heat content, surface temperature, and evaporation. Geophysical Research Letters 42:7 pp. (DOI:10.1002/2015GL063799) (2015).
Since the late 1990s, the Laurentian Great Lakes have experienced persistent low water levels and above average over-lake evaporation rates. During the winter of 2013–2014, the lakes endured the most persistent, lowest temperatures and highest ice cover in recent history, fostering speculation that over-lake evaporation rates might decrease and that water levels might rise. To address this speculation, we examined interseasonal relationships in Lake Michigan’s thermal regime. We find pronounced relationships between winter conditions and subsequent fall heat content, modest relationships with fall surface temperature, but essentially no correlation with fall evaporation rates. Our findings suggest that the extreme winter conditions of 2013–2014 may have induced a shift in Lake Michigan’s thermal regime and that this shift coincides with a recent (and ongoing) rise in Great Lakes water levels. If the shift persists, it could (assuming precipitation rates remain relatively constant) represent a return to thermal and hydrologic conditions not observed on Lake Michigan in over 15 years.
GRONEWOLD, A.D., A.H. CLITES, J. Bruxer, K.A. Kompoltowicz, J.P. SMITH, T.S. HUNTER, and C. Wong. Water levels surge on the Great Lakes. Eos 96(6):7 pp. (DOI:10.1029/2015EO026023) (2015). https://eos.org/project-updates/water-levels-surge-on-great-lakes
Water levels on Lake Superior and Lake Michigan-Huron (Lake Michigan and Lake Huron are commonly viewed as a single lake from a long-term hydrological perspective), the two largest lakes on Earth by surface area, rose at a remarkable rate over the past 2 years. The recent surge represents one of the most rapid rates of water level change on the Great Lakes in recorded history and marks the end of an unprecedented period of below-average water levels that began in 1998.
GRONEWOLD, A.D., A.H. CLITES, and L. Rear-McLaughlin. Great Lakes water levels: Monitoring change in Earth's largest surface freshwater system. In Clear Waters. New York Water Environment Association, Inc., Syracuse, NY, 16-18 pp. (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150036.pdf
The Great Lakes, their connecting waterways and their watersheds, comprise the largest surface freshwater system on Earth. They are a dominant physical feature of North America and form part of the political boundary between the U.S. and Canada. The Great Lakes contain nearly 20 percent of the workd's fresh surfce water and have a coastline longer than the east of west coast of the US. One-third of the North American population lives within the Great Lakes watershed. The lakes provide drinking water to 40 million people as well as abundant aquatic recreation and beauty.
He, J.X., J.R. Bence, C.P. Madenjian, S.A. POTHOVEN, N.E. Dobiesz, D.G. Fielder, J.L. Johnson, M.P. Ebener, A.R. Cottrill, L.C. Mohr, and S.R. Koproski. Coupling age structured stock assessment and fish bioenergetics models: A system of time-varying models for quantifying piscivory patterns during the rapid trophic shift in the main basin of Lake Huron. Canadian Journal of Fisheries and Aquatic Sciences 72(1):7-23 (DOI:10.1139/cjfas-2014-0161) (2015).
We quantified piscivory patterns in the main basin of Lake Huron during 1984–2010 and found that the biomass transfer from prey fish to piscivores remained consistently high despite the rapid major trophic shift in the food webs. We coupled age-structured stock assessment models and fish bioenergetics models for lake trout (Salvelinus namaycush), Chinook salmon (Oncorhynchus tshawytscha), walleye (Sander vitreus), and lake whitefish (Coregonus clupeaformis). The model system also included time-varying parameters or variables of growth, length–mass relations, maturity schedules, energy density, and diets. These time-varying models reflected the dynamic connections that a fish cohort responded to year-to-year ecosystem changes at different ages and body sizes. We found that the ratio of annual predation by lake trout, Chinook salmon, and walleye combined with the biomass indices of age-1 and older alewives (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax) increased more than tenfold during 1987–2010, and such increases in predation pressure were structured by relatively stable biomass of the three piscivores and stepwise declines in the biomass of alewives and rainbow smelt. The piscivore stability was supported by the use of alternative energy pathways and changes in relative composition of the three piscivores. In addition, lake whitefish became a new piscivore by feeding on round goby (Neogobius melanostomus). Their total fish consumption rivaled that of the other piscivores combined, although fish were still a modest proportion of their diet. Overall, the use of alternative energy pathways by piscivores allowed the increases in predation pressure on dominant diet species.
HUNTER, T.S., A.H. CLITES, A.D. GRONEWOLD, and K.B. CAMPBELL. Development and application of a North American Great Lakes hydrometeorological database - Part I: Precipitation, evaporation, runoff, and air temperature. Journal of Great Lakes Research 41(1):65-77 (DOI:10.1016/j.jglr.2014.4.12.006) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150006.pdf
Starting in 1983, the National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory (GLERL) has been developing and maintaining a historical time series of North American Great Lakes basin-scale monthly hydrometeorological data. This collection of data sets, which we hereafter refer to as the NOAA-GLERL monthly hydrometeorological database (GLM-HMD), is, to our knowledge, the first (and perhaps still the only) to assimilate hydrometeorological measurements into model simulations for each of the major components of the water budget across the entirety (i.e., both United States and Canadian portions) of the Great Lakes basin for a period of record dating back to the early and mid 1900s. Here, we describe the development of data sets in the first (GLM-HMD-I) of two subsets of the GLM-HMD including basin-scale estimates of over-lake and over-land precipitation and air temperature, runoff, and over-lake evaporation. Our synthesis of the GLM-HMD-I includes a summary of the monitoring network associated with each variable and an indication of how each monitoring network has changed over time. We conclude with two representative applications of the GLM-HMD aimed at advancing understanding of seasonal and long-term changes in Great Lakes regional meteorology and climatology. These two examples implicitly reflect the historical utility of the GLM-HMD in numerous previous studies, and explicitly demonstrate its potential utility in ongoing and future regional hydrological science and climate change research.
IVAN, L.N., and T.O. Hook. Energy allocation strategies of young temperate fish: An eco-genetic modeling approach. Canadian Journal of Fisheries and Aquatic Sciences 72(8):1243-1258 (DOI:10.1139/cjfas-2014-0197) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150034.pdf
We use an individual-based eco-genetic model to explore the relative selective pressures of size-dependent predation, overwinter mortality, and density-dependent energy acquisition in structuring plastic and adaptive energy allocation during the first year of life of a temperate fish population. While several patterns emerging from a suite of eco-genetic model simulations were consistent with past theoretical models and empirical evaluations of energy allocation by young fishes, results also highlight the utility of eco-genetic models for simultaneous consideration of plastic and adaptive processes. Across simulations, variation in genetic control of energy allocation was limited during very early ontogeny when size-dependent predation pressure was particularly high. While this stabilizing selection on energy allocation diminished later in the growing season, predation, overwinter mortality, and density-dependent processes simultaneously structured energy partitioning later in ontogeny through the interactive influence of plastic and adaptive processes. Specifically, high risk of overwinter mortality and low predation selected for high prioritization of energy storage. We suggest that simulations demonstrate the utility of eco-genetic models for generating null predictions of how selective pressures may structure expression of life history traits, such as early life energy allocation.
Jiang, L., M. Xia, S.A. Ludsin, E.S. RUTHERFORD, D.M. MASON, J.M. Jarrin, and K.L. Pangle. Biophysical modeling assessment of the drivers for plankton dynamics in dreissenid-colonized western Lake Erie. Ecological Modelling 308:18-33 (2015).
Given that phytoplankton and zooplankton communities have served as key ecological indicators of anthropogenic and other perturbations, a high-resolution Finite Volume Coastal Ocean Model (FVCOM) based Integrated Compartment Model (FVCOM-ICM) was implemented to investigate plankton dynamics with the inclusion of dreissenid invasion in Lake Erie, particularly in the most productive western basin. After identifying suitable horizontal and vertical resolutions that allowed for accurate depiction of in-lake nutrient concentrations and plankton biomass, we explored how variation in nutrient (phosphorus, nitrogen) loading and dreissenid mussel density could influence plankton dynamics. Our scenario-testing showed that western Lake Erie’s phytoplankton community appeared more limited by phosphorus than nitrogen on both seasonal and interannual scales with light limitation occurring in the nearshore and Maumee River plume areas. Dreissenid mussel impacts varied temporally, with phytoplankton communities being highly influenced by dreissenid nutrient excretion at times (under low nutrient availability) and dreissenid grazing at other times (under bloom conditions). It was concluded that the effect of zooplankton predation on phytoplankton was stronger than that of dreissenid mussels, and that multiple algal groups could promote the efficiency of nutrient assimilation and the overall plankton production. Additionally, river inputs and wind-driven water circulation were important by causing heterogeneity in habitat conditions through nutrient advection and vertical mixing, and wind-induced surface waves could result in non-negligible down-wind redistribution of plankton biomass, which increased with wind/wave magnitude.
JOSHI, S.J., A. Stevens, and L. Vaccaro. Saginaw Bay Multiple Stressors and Beyond workshop: Summary report. NOAA Technical Memorandum GLERL-166. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 28 pp. (2015). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-166/tm-166.pdf
Saginaw Bay has been and continues to be exposed to many stressors from anthropogenic activities, including toxic contaminants, nutrients, sediments, overfishing, exotic species, and declining water levels. In response, the NOAA Great Lakes Environmental Research Laboratory (GLERL), the Cooperative Institute for Limnology and Ecosystems Research (CILER), and other partner institutions began a five-year Saginaw Bay Multiple Stressors Project sponsored by the Center for Sponsored Coastal Ocean Research (CSCOR) in 2007, evaluating the impacts of these stressors and their combined effects on Saginaw Bay and their management implications. With the project coming to an end in 2012, a dialogue with the scientists and representatives from the Michigan Departments of Natural Resources (DNR) and Environmental Quality (DEQ), Michigan Sea Grant, and other organizations was necessary in order to decide how to best convey the project results and prioritize next steps for future research in Saginaw Bay. This dialogue was conducted through an all-day needs assessment workshop with the goal of receiving input and feedback on remaining research and outreach needs in Saginaw Bay and gaining recommendations for continued research to build upon the Multiple Stressors Project. Additionally the workshop aimed at identifying any remaining gaps in research and outreach efforts in Saginaw Bay and to determine where NOAA and Michigan Sea Grant should begin prioritizing research and outreach and education programs. This report describes the results of the workshop including remaining issues and needs identified as well as priorities for future research, and strategies and recommendations for next steps.
Kao, Y.C., C.P. Madenjian, D.B. Bunnell, B.M. LOFGREN, and M. PERROUD. Temperature effects induced by climate change on the growth and consumption by salmonines in Lakes Michigan and Huron. Environmental Biology of Fishes 98:1089-1104 (DOI:10.1007/s10641-014-0352-6) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2014/20140059.pdf
We used bioenergetics models to investigate temperature effects induced by climate change on the growth and consumption by Chinook salmon Oncorhynchus tshawytscha, lake trout Salvelinus namaycush, and steelhead O. mykiss in Lakes Michigan and Huron. We updated biological inputs to account for recent changes in the food webs and used temperature inputs in response to regional climate observed in the baseline period (1964–1993) and projected in the future period (2043–2070). Bioenergetics simulations were run across multiple age-classes and across all four seasons in different scenarios of prey availability. Due to the increased capacity of prey consumption, future growth and consumption by these salmonines were projected to increase substantially when prey availability was not limited. When prey consumption remained constant, future growth of these salmonines was projected to decrease in most cases but increase in some cases where the increase in metabolic cost can be compensated by the decrease in waste (egestion and excretion) loss. Consumption by these salmonines was projected to increase the most during spring and fall when prey energy densities are relatively high. Such seasonality benefits their future growth through increasing annual gross energy intake. Our results indicated that lake trout and steelhead would be better adapted to the warming climate than Chinook salmon. To maintain baseline growth into the future, an increase of 10 % in baseline prey consumption was required for Chinook salmon but considerably smaller increases, or no increases, in prey consumption were needed by lake trout and steelhead.
Kao, Y.C., C.P. Madenjian, D.B. Bunnell, B.M. LOFGREN, and M. PERROUD. Potential effects of climate change on the growth of fishes from different thermal guilds in Lakes Michigan and Huron. Journal of Great Lakes Research 41:423-435 (DOI:10.1016/j.jglr.2015.03.012) (2015).
We used a bioenergetics modeling approach to investigate potential effects of climate change on the growth of two economically important native fishes: yellow perch (Perca flavescens), a cool-water fish, and lake whitefish (Coregonus clupeaformis), a cold-water fish, in deep and oligotrophic Lakes Michigan and Huron. For assessing potential changes in fish growth, we contrasted simulated fish growth in the projected future climate regime during the period 2043–2070 under different prey availability scenarios with the simulated growth during the baseline (historical reference) period 1964–1993. Results showed that effects of climate change on the growth of these two fishes are jointly controlled by behavioral thermoregulation and prey availability. With the ability of behavioral thermoregulation, temperatures experienced by yellow perch in the projected future climate regime increased more than those experienced by lake whitefish. Thus simulated future growth decreased more for yellow perch than for lake whitefish under scenarios where prey availability remains constant into the future. Under high prey availability scenarios, simulated future growth of these two fishes both increased but yellow perch could not maintain the baseline efficiency of converting prey consumption into body weight. We contended that thermal guild should not be the only factor used to predict effects of climate change on the growth of a fish, and that ecosystem responses to climate change should be also taken into account.
Kopf, A., T.W. DAVIS, and among 154 others. The Ocean Sampling Day consortium. GigaScience 4(27):5 (DOI:10.1186/s13742-015-0066-5) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150038.pdf
Ocean Sampling Day was initiated by the EU-funded Micro B3 (Marine Microbial Biodiversity, Bioinformatics, Biotechnology) project to obtain a snapshot of the marine microbial biodiversity and function of the world’s oceans. It is a simultaneous global mega-sequencing campaign aiming to generate the largest standardized microbial data set in a single day. This will be achievable only through the coordinated efforts of an Ocean Sampling Day Consortium, supportive partnerships and networks between sites. This commentary outlines the establishment, function and aims of the Consortium and describes our vision for a sustainable study of marine microbial communities and their embedded functional traits.
Krueger, D.M., E.S. RUTHERFORD, and D.M. MASON. Foraging ecology of walleye and brown trout in a Great Lakes tributary. Journal of Great Lakes Research:8 pp. (DOI:DOI:10.1016/j.jglr.2015.10.016) (2015).
The role of alternative prey on predator diet selection and survival of juvenile (parr) Chinook salmon (Oncorhynchus tshawytscha) is not well understood in the Laurentian Great Lakes. Therefore, measures of predator foraging ecology (prey species and size selection), prey densities, and functional response relationships were determined for adult walleye (Sander vitreus) and brown trout (Salmo trutta) (hatchery-reared) feeding on parr and alternate prey in the Muskegon River, a tributary of Lake Michigan, USA, from 2004 to 2007. Walleye selected for smaller than average brown trout and rainbow trout (hatchery-reared) butwalleye prey size (within-prey) was independent of predator size. In general, walleye showed neutral selection for all prey species but, in some years, showed positive selection for rainbow trout and negative selection for parr. Hatchery-reared brown trout selected the smallest parr in the environment although prey size was independent of predator size. Parr were positively selected by brown trout only in April. Functional response curves were fit to describe the consumption of parr and other prey types by walleye (type II) and brown trout (type I). Interactions among rainbow trout, walleye, and brown trout favored parr survival, i.e. the presence of alternate prey (rainbow trout) significantly influenced walleye predation on parr,while brown trout appeared to become quickly limited by size or escape ability of parr. Our results should enhance understanding of food web dynamics in Great Lakes tributary habitats.
Lei, R., H. Xie, J. WANG, M. Lepparanta, I. Jonsdottir, and Z. Zhang. Changes in sea ice concentrations along the Arctic Northeast Passage from 1979 to 2012. Cold Regions Science and Technology 119:132-144 (DOI:10.1016/j.coldregions.2015.08.004) (2015).
Sea ice conditions in the Arctic Northeast Passage (NEP) have changed dramatically in the last four decades, with important impacts on the environment and navigability. In the present study, multisource remote sensing data for 1979–2012 were analyzed to quantify seasonal, interannual, and spatial changes in sea ice conditions along the NEP. Data for October–November showed that spatially averaged ice thickness in the NEP decreased from 1.2–1.3min 2003–2006 to 0.2–0.6min 2011–2012. From 1979 to 2012, the fastest decreasing trend in monthly ice concentration occurred in October (−1.76% per year, P b 0.001), when the ice cover starts to increase. As a result of decreasing multiyear sea ice, thinning ice and delayed freeze-up, the spatially averaged length of open period (ice concentration b 50%) increased from 84 days in the 1980s to 114 days in the 2000s and reached 146 days in 2012. The Kara, Laptev, and East Siberian sectors were relatively inaccessible, especially the sector of 90–110°E around the Vilkitsky Strait. However, because of the thinning sea ice prior to the melt season and the enhanced positive polarity of the summer Arctic Dipole Anomaly, these sectors have become more accessible in recent years. The summer sea ice along the high-latitude sea route (HSR) north of the eastern Arctic islands, with a route distance comparable to the NEP, has also decreased during the last decade with the ice-free period reaching 42 days in 2012. The HSR avoids shallowwaters along the coast, improving access to the Arctic sea route for deeper-draft vessels
Liao, X., Y. Du, H. Zhan, P. Shi, and J. WANG. Summertime phytoplankton blooms and surface cooling in the western south equatorial Indian Ocean. Journal of Geophysical Research - Oceans 119:7687-7704 (DOI:10.1002/2014JC010195) (2015).
Chlorophyll-a (Chla) concentration derived from the Sea viewing Wide field of View sensor (SeaWiFS) data (January 1998 to December 2010) shows phytoplankton blooms in the western south equatorial Indian Ocean (WSEIO) during the summer monsoon. The mechanism that sustains the blooms is investigated with the high-resolution Ocean General Circulation Model for the Earth Simulator (OFES) products. The summer blooms in the WSEIO are separated from the coast; they occur in June, reach their maximum in August, and decay in October. With summer monsoon onset, cross-equatorial wind induces open-ocean upwelling in the WSEIO, uplifting the nutricline. The mixed layer heat budget analysis reveals that both thermal forcing and ocean processes are important for the seasonal variations of SST, especially wind-driven entrainment plays a significant role in cooling the WSEIO. These processes cause nutrient enrichment in the surface layer and trigger the phytoplankton blooms. As the summer monsoon develops, the strong wind deepens the mixed layer; the entrainment thus increases the nutrient supply and enhances the bloom. Horizontal advection associated with the Southern Gyre might also be an important process that sustains the bloom. This large clockwise gyre could advect nutrient-rich water along its route, allowing Chla to bloom in a larger area.
Link, J., D.M. MASON, T. Lederhouse, S. Gaichas, T. Hartley, J. Ianeli, R. Methot, C. Stock, C.A. STOW, and H. Townsend. Report from the Joint OAR-NMFS Modeling Uncertainty Workshop. NOAA Technical Memorandum NMFS-F/SPO-153. NOAA National Marine Fisheries Office of Science and Technology, Silver Spring, MD, 31 pp. (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/NOAA_TM_NMFS-F_SPO-153.pdf
The National Oceanic and Atmospheric Administration’s (NOAA’s) Office of Oceanic and Atmospheric Research (OAR) and National Marine Fisheries Service (NMFS) held a joint workshop April 13–15, 2015, at NOAA’s Great Lakes Environmental Research Laboratory in Ann Arbor, Michigan, to examine methods and means of addressing, reviewing, and presenting uncertainty in ecosystem and living marine resource models and assessments. This workshop explored the range of practices used within OAR, NMFS, and other organizations in the modeling community to deal with uncertainty, developed a set of best practices, and identified recommendations to better address model output uncertainty and improve model skill. A broad range of NOAA’s living marine resource and ecosystem modeling approaches were discussed. Examples from these and related disciplines show a healthy and robust gradient of models along multiple dimensions of complexity. As such, continued model development remains an important research activity and should include evaluations of model uncertainty. Best approaches to address uncertainties depend on the type of model and application. In this context, the workshop focused on model skill evaluation, noting the need for and feasibility of multiple measures. Participants identified 14 best practices at the workshop that will serve ongoing and future efforts to address model uncertainty. A simple “cheat sheet” on matching approaches with specific types of uncertainty across model applications was suggested. This could lead to a template of standard reporting for living marine resource and ecosystem assessment outputs. The benefits of having a common usage of quantitative information to explore model skill would provide the public with a more consistent communication of scientific results and management implications. Some of the key practices that emerged included the use of multi-model inference, adoption of management strategy evaluations, and improved use of communication tools. These formed the basis of eight recommendations specific to model efforts. Overall, cross-disciplinary, cross-organizational meetings like this to coordinate and advance modeling efforts were considered useful and should continue. Next steps recommended are: (1) Seek NOAA leadership support for a full range of quantitative modeling efforts across the spectrum of complexity and disciplinary emphasis in support of living marine resource management mandates. (2) Establish routine and regular venues for the NOAA modeling community to meet and interact. (3) Support and advance cross-line-office and cross-disciplinary (including social science) coordination on model development.
LIU, P.C., R. Bouchard, W.E. Rogers, A.V. Babanin, and D.W. Wang. Is there a wind connection to freaque wave occurrences? Natural Hazards and Earth System Sciences 15:1-17 (DOI:10.5194/nhessd-15-1-2015) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150004.pdf
There was a recent freaque wave encounter near Scituate, Massachusetts by a local transport ferry en route from Provincetown to Boston. The encounter resulted in minimal damages, fortunately, and provided us a chance to examine a possible connection between the freaque wave occurrence and the ambient wind field, since the place of encounter was in the vicinity of a NOAA NDBC buoy where wind and wave data were recorded. Here we present a brief analysis. In particular, we found it is plausible that the freaque wave was the result of a wind speed reduction in the wind field that preceded its occurrence.
LOFGREN, B.M., and J. Rouhana. Reaffirmation of large biases in a long-used method for projecting changes in Great Lakes water levels. NOAA Technical Memorandum GLERL-167. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 25 pp. (2015). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-167/tm-167.pdf
A method for projecting the water levels of the Laurentian Great Lakes under scenarios of human-caused climate change, used almost to the exclusion of other methods in the past, relies very heavily on the Large Basin Runoff Model (LBRM) as a component for determining the water budget for the lake system. This model uses near-surface air temperature as a primary predictor of evapotranspiration (ET); in addition to previous published work, we show here again that its very high sensitivity to temperature makes it overestimate ET in a way that is highly inconsistent with the fundamental principle of conservation of energy at the land surface. Under the traditional formulation, the quantity that has been called “energy available for evapotranspiration,” which is proportional to what we call “potential evapotranspiration” (PET), is increased by large factors in future scenarios—by a factor of nearly 600 in the Lake Superior basin under forcing by one GCM case, but more typically by factors between 3 and 10. Because of the way that LBRM is formulated and calibrated, these factors can be thought of as corresponding to the factor of increase in solar radiation incident on the Earth, or, more vividly, as the number of Suns present in the sky of the virtual world simulated by LBRM. Therefore, we have created alternative formulations, which we regard as more reflective of what is being simulated by the driving GCMs, for the way that climate change is ingested into the modeling system that includes LBRM. In addition to the energy adjustment method in which PET is increased by an amount proportional to the change in net radiative energy at the surface, we add the Priestley-Taylor method, which augments the energy adjustment method by inclusion of a temperature-dependent factor with rigorous theoretical underpinnings that is a much weaker function of temperature than in the LBRM’s basic formulation, as well as the Clausius-Clapeyron method, in which the PET is increased by an amount proportional to the increase in water vapor capacity of the atmosphere, again a weaker function of temperature than in the LBRM. We establish that all three of these alternative methods show, relative to the traditional method, often astoundingly less PET and less ET, more runoff from the land and net basin supply for the lake basins, and higher lake water levels in the future. The magnitude of these discrepancies is highly correlated with the air temperature change in the driving GCM (larger temperature changes lead to larger discrepancies). Using various methods of estimating the statistical significance, we find that, at minimum, these discrepancies in results are significant at the 99.998% level.
Lynch, A.J., W.W. Taylor, T.D. Beard, and B.M. LOFGREN. Climate change projections for lake whitefish (Coregonus clupeaformis) recruitment in the 1836 Treaty Waters of the upper Great Lakes. Journal of Great Lakes Research 41(2):415-422 (DOI:10.1016/j.jglr.2015.03.015) (2015).
Lake whitefish (Coregonus clupeaformis) is an ecologically, culturally, and economically important species in the Laurentian Great Lakes. Lake whitefish have been a staple food source for thousands of years and, since 1980, have supported the most economically valuable (annual catch value≈US$16.6 million) and productive (annual harvest ≈ 7 million kg) commercial fishery in the upper Great Lakes (Lakes Huron, Michigan, and Superior). Climate changes, specifically changes in temperature, wind, and ice cover, are expected to impact the ecology, production dynamics, and value of this fishery because the success of recruitment to the fishery has been linked with these climatic variables. We used linear regression to determine the relationship between fall and spring air temperature indices, fall wind speed, winter ice cover, and lake whitefish recruitment in 13 management units located in the 1836 Treaty Waters of the Upper Great Lakes ceded by the Ottawa and Chippewa nations, a culturally and commercially important region for the lake whitefish fishery. In eight of the 13 management units evaluated, models including one or more climate variables (temperature, wind, ice cover) explained significantly more variation in recruitment than models with only the stock–recruitment relationship, using corrected Akaike's Information Criterion comparisons (ΔAICc > 3). Isolating the climate–recruitment relationship and projecting recruitment with the Coupled Hydrosphere-Atmosphere Research Model (CHARM) indicated the potential for increased lake whitefish recruitment in the majority of the 1836 Treaty Waters management units. These results can inform adaptive management strategies by providing anticipated implications of climate on lake whitefish recruitment.
MIEHLS, A.L.J., S.D. Peacor, L. Valliant, and A.G. McAdam. Evolutionary stasis despite selection on a heritable trait in an invasive zooplankton. Journal of Evolutionary Biology 28(5):1091-1102 (DOI:10.1111/jeb.12632) (2015).
Invasive species are one of the greatest threats to ecosystems, and there is evidence that evolution plays an important role in the success or failure of invasions. Yet, few studies have measured natural selection and evolutionary responses to selection in invasive species, particularly invasive animals. We quantified the strength of natural selection on the defensive morphology (distal spine) of an invasive zooplankton, Bythotrephes longimanus, in Lake Michigan across multiple months during three growing seasons. We used multiple lines of evidence, including historic and contemporary wild-captured individuals and palaeoecology of retrieved spines, to assess phenotypic change in distal spine length since invasion. We found evidence of temporally variable selection, with selection for decreased distal spine length early in the growing season and selection for increased distal spine length later in the season. This trend in natural selection is consistent with seasonal changes in the relative strength of non-gape-limited and gape-limited fish predation. Yet, despite net selection for increased distal spine length and a known genetic basis for distal spine length, we observed little evidence of an evolutionary response to selection. Multiple factors likely limit an evolutionary response to selection, including genetic correlations, trade-offs between components of fitness, and phenotypic plasticity.
Music, B., A. Frigon, B.M. LOFGREN, R. Turcotte, and J.F. Cyr. Present and future Laurentian Great Lakes hydroclimatic conditions as simulated by regional climate models with an emphasis on Lake Michigan-Huron. Climatic Change 130(4):603-618 (DOI:10.1007/s10584-015-1348-8) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150029.pdf
Regional climate modelling represents an appealing approach to projecting Great Lakes water supplies under a changing climate. In this study, we investigate the response of the Great Lakes Basin to increasing greenhouse gas and aerosols emissions using an ensemble of sixteen climate change simulations generated by three different Regional Climate Models (RCMs): CRCM4, HadRM3 and WRFG. Annual and monthly means of simulated hydrometeorological variables that affect Great Lakes levels are first compared to observation-based estimates. The climate change signal is then assessed by computing differences between simulated future (2041–2070) and present (1971–1999) climates. Finally, an analysis of the annual minima and maxima of the Net Basin Supply (NBS), derived from the simulated NBS components, is conducted using Generalized Extreme Value distribution. Results reveal notable model differences in simulated water budget components throughout the year, especially for the lake evaporation component. These differences are reflected in the resulting NBS. Although uncertainties in observation-based estimates are quite large, our analysis indicates that all three RCMs tend to underestimate NBS in late summer and fall, which is related to biases in simulated runoff, lake evaporation, and over-lake precipitation. The climate change signal derived from the total ensemble mean indicates no change in future mean annual NBS. However, our analysis suggests an amplification of the NBS annual cycle and an intensification of the annual NBS minima in future climate. This emphasizes the need for an adaptive management of water to minimize potential negative implications associated with more severe and frequent NBS minima.
Niu, Q., M. Xia, E.S. RUTHERFORD, D.M. MASON, E.J. ANDERSON, and D.J. SCHWAB. Investigation of interbasin exchange and interannual variability in Lake Erie using an unstructured-grid hydrodynamic model. Journal of Geophysical Research - Oceans 120:21 pp. (DOI:10.1002/2014JC010457) (2015).
Interbasin exchange and interannual variability in Lake Erie’s three basins are investigated with the help of a three-dimensional unstructured-grid-based Finite Volume Coastal Ocean Model (FVCOM). Experiments were carried out to investigate the influence of grid resolutions and different sources of wind forcing on the lake dynamics. Based on the calibrated model, we investigated the sensitivity of lake dynamics to major external forcing, and seasonal climatological circulation patterns are presented and compared with the observational data and existing model results. It was found that water exchange between the western basin (WB) and the central basin (CB) was mainly driven by hydraulic and density-driven flows, while density-driven flows dominate the interaction between the CB and the eastern basin (EB). River-induced hydraulic flows magnify the eastward water exchange and impede the westward one. Surface wind forcing shifts the pathway of hydraulic flows in the WB, determines the gyre pattern in the CB, contributes to thermal mixing, and magnifies interbasin water exchange during winter. Interannual variability is mainly driven by the differences in atmospheric forcing, and is most prominent in the CB.
O’Reilly, C.M., and G.A. LESHKEVICH (among 56 others). Rapid and highly variable warming of lake surface waters around the globe. Geophysical Research Letters 42(DOI:10.1002/2015GL066235) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150053.pdf
In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean= 0.34 deg C decade-1) between 1985-2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors- from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72 deg C decade-1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53 deg C decade-1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.
Pisareva, M.N., R.S. Packart, K. Iken, E.A. Ershova, J.M. Grebmeier, L.W. Cooper, B.A. Bluhm, C. Nobre, R.R. Hopcroft, H. HU, J. WANG, C.J. Ashjian, K.N. Kosobokova, and T.E. Whiteledge. The relationship between patterns of benthic fauna and zooplankton in the chukchi sea and physical forcing. Oceanography 28(3):68-83 (DOI:10.5670/oceanog.2015.58) (2015).
Using data from a number of summer surveys of the Chukchi Sea over the past decade, we investigate aspects in which the benthic fauna, sediment structure, and zooplankton there are related to circulation patterns and shelf hydrographic conditions. A flow speed map is constructed that reveals the major pathways on the shelf. Regions of enhanced flow speed are dictated by lateral constrictions—in particular, Bering Strait and Barrow and Herald Canyons—and by sloping topography near coastlines. For the most part, benthic epifaunal and macrofaunal suspension feeders are found in high flow regimes, while deposit feeders are located in regions of weaker flow. The major exceptions are in Bering Strait, where benthic sampling was underrepresented, and in Herald Canyon where the pattern is inexplicably reversed. Sediment grain size is also largely consistent with variations in flow speed on the shelf. Data from three biophysical surveys of the Chukchi Sea, carried out as part of the Russian-American Long-term Census of the Arctic program, reveal close relationships between the water masses and the zooplankton communities on the shelf. Variations in atmospheric forcing, particularly wind, during the three sampling periods caused significant changes in the lateral and vertical distributions of the summer and winter water masses. These water mass changes, in turn, were reflected in the amounts and species of zooplankton observed throughout the shelf in each survey. Our study highlights the close relationship between physical drivers (wind forcing, water masses, circulation, and sediment type) in the Chukchi Sea and the biological signals in the benthos and the plankton on a variety of time scales.
POTHOVEN, S.A., and G.L. Fahnenstiel. Spatial and temporal trends in zooplankton assemblages along a nearshore to offshore transect in southeastern Lake Michigan from 2007-2012. Journal of Great Lakes Research - Special Section on Lake Michigan Interactions 41:9 pp. (DOI:10.1016/j.jglr.2014.09.015) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150012.pdf
Zooplankton were collected at a nearshore (15 m depth), a mid-depth (45 m) and an offshore site (110 m) near Muskegon, Michigan during March–December in 2007–2012. On a volumetric basis, biomass was lower at the nearshore site relative to the mid-depth site, but overall biomass at the nearshore and offshore sites did not differ. Differences in zooplankton assemblages among sites were due largely to Diaptomidae, Limnocalanus macrurus, Daphnia galeata mendotae, Cyclops, and either Bosmina longirostris or Bythotrephes longimanus. Diaptomidae were the most abundant group, accounting for 56–66% of zooplankton biomass across sites. Herbivorous cladocerans accounted for 14–22% of zooplankton biomass across sites, with B. longirostris dominant at the nearshore site and D. g. mendotae dominant at the mid-depth and offshore sites. Bythotrephes was the most abundant predatory cladoceran at all sites although, at the nearshore site, it was only abundant in the fall. There was a higher percentage of large-bodied zooplankton groups in the offshore and mid-depth zones relative to the nearshore zone. Declines in zooplankton biomass relative to the 1970s have occurred across all sites. In addition to seasonal variation within a site, we noted annual variation, especially at the offshore site, with the zooplankton assemblage during 2007–2008 differing from that found in 2010–2012 due to increases in D. g. mendotae and Cyclops and decreases in B. longimanus and L. macrurus in 2010–2012.
POTHOVEN, S.A., and T.O. Hook. Feeding ecology of invasive age-0 white perch and native white bass after two decades of co-existence in Saginaw Bay, Lake Huron. Aquatic Invasions 10(3):347-357 (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150008.pdf
The diets and energy content of sympatric populations of invasive age-0 white perch Morone americana and native age-0 white bass Morone chrysops were evaluated in Saginaw Bay, Lake Huron following >20 years of coexistence. Fish were collected during July-November in 2009 and 2010 to assess seasonal and interannual patterns of diet composition, diet similarity, feeding strategy and energy density for the two species. The diet composition by weight of age-0 white bass was dominated by various zooplankton taxa, fish, or emergent insects, depending on the month and year. Although fish occasionally comprised a large fraction of the diet biomass, they were eaten by <24% of white bass each month. The diet composition of age-0 white perch shifted from one dominated by chironomids and other benthic macroinvertebrates in 2009 to one largely consisting of Daphnia spp. in 2010. There was more overlap in standardized diet assemblages in 2010 than in 2009 due to the increased importance of Daphnia spp. in white perch diets in 2010. Contrary to expectations, complete separation of diets was not a requirement that enabled the long-term coexistence of invasive white perch and native white bass in Saginaw Bay. Both age-0 white bass and white perch had a mixed feeding strategy with varying degrees of specialization and generalization on different prey. The inter-annual variation in prey, i.e., higher densities of zooplankton in 2009 and chironomids in 2010, is directly opposite of the pattern observed in white perch diets, i.e., diets dominated by chironomids in 2009 and zooplankton in 2010. Energy density increased from July into autumn/fall for both species suggesting that food limitation was not severe.
Ptachnikova, R., H.A. VANDERPLOEG, and J.F. CAVALETTO. Big versus small: Does Bythotrephes longimanus predatiaon regulate spatial distribution of another invasive predatory cladoceran, Cercopagis pengoi? Journal of Great Lakes Research 41(Supplement 3):7 (DOI:10.1016/j.jglr.2015.10.006) (2015).
Offshore–onshore spatial distribution and abundance of Cercopagis pengoi, a small non-indigenous predatory cercopagid, in Lake Michigan have been hypothesized to be regulated by the larger non-indigenous predatory cercopagid, Bythotrephes longimanus, through predation and/or competition. However, temperature and prey abundance are other factors that could be affecting Cercopagis. First, we examined all these factors on Cercopagis population abundance, life history traits and spatio-temporal distribution. In addition, we examined vertical spatial overlap between these species and determined predation rate of Bythotrephes on Cercopagis. Linear mixed effects analysis of spatial–temporal data showed that biomass of B. longimanus had the strongest effect which was significantly negative on biomass, proportion of fecund females and mean clutch size of Cercopagis. Fecundity increased significantly with density of potential prey zooplankton, whereas Cercopagis total biomass increased significantly with the mean epilimnion temperature. Cercopagis and Bythotrephes overlapped vertically in the epi- and metalimnion, and neither of them showed any appreciable diel vertical migration. In predation experiments, Bythotrephes consumed Cercopagis at the same rate as Daphnia mendotae, a known preferred prey, when offered at equal concentrations. Overall, this observation, togetherwith vertical overlap of Cercopagis with Bythotrephes implies that Bythotrephes predation has a strong influence on Cercopagis distribution; however, prey availability, temperature, and competition may be important secondary factors. These results imply tha invasion success of Cercopagis may be limited by prior invasion by Bythotrephes.
QIAN, S.S., C.A. STOW, and Y.K. Cha. Implications of Stein's paradox in environmental standard compliance assessment. Environmental Science & Technology 49(10):5913-5920 (DOI:10.1021/acs.est.5b00656) (2015).
The implications of Stein’s paradox stirred considerable debate in statistical circles when the concept was first introduced in the 1950s. The paradox arises when we are interested in estimating the means of several variables simultaneously. In this situation, the best estimator for an individual mean, the sample average, is no longer the best. Rather, a shrinkage estimator, which shrinks individual sample averages toward the overall average is shown to have improved overall accuracy. Although controversial at the time, the concept of shrinking toward overall average is now widely accepted as a good practice for improving statistical stability and reducing error, not only in simple estimation problems, but also in complicated modeling problems. However, the utility of Stein’s insights are not widely recognized in the environmental management community, where mean pollutant concentrations of multiple waters are routinely estimated for management decision-making. In this essay, we introduce Stein’s paradox and its modern generalization, the Bayesian hierarchical model, in the context of environmental standard compliance assessment. Using simulated data and nutrient monitoring data from wadeable streams around the Great Lakes, we show that a Bayesian hierarchical model can improve overall estimation accuracy, thereby improving our confidence in the assessment results, especially for standard compliance assessment of waters with small sample sizes.
ROWE, M.D., E.J. ANDERSON, J. WANG, and H.A. VANDERPLOEG. Modeling the effect of invasive quagga mussels on the spring phytoplankton bloom in Lake Michigan. Journal of Great Lakes Research 41:17 pp. (DOI:10.1016/j.jglr.2014.12.018) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150011.pdf
The disappearance of the spring phytoplankton bloom in Lake Michigan has been attributed in some studies to the direct effect of quagga mussel filter-feeding. We applied a biophysical model to test whether the observed reduction in the spring bloom can be explained by direct effects of quagga mussel grazing. We developed a 1-D column biological model that simulated light and temperature limitation on phytoplankton growth, vertical mixing, and grazing by zooplankton and quagga mussels. We applied the 3-D finite volume coastal ocean model (FVCOM) to provide vertical mixing, with two scenarios of atmospheric forcing: (a) North American Regional Reanalysis (NARR) and (b) station interpolation using the Natural Neighbor Method. Simulated development of the spring bloom and formation of the deep chlorophyll layer in the early summer stratified period were consistent with observations. Increased strength of winter stratification (surface b 4 °C) in 1997 (cold spring) increased chlorophyll concentrations during March and April, compared to 1998, by reducing light limitation (reduced mixed-layer depth). Simulations with NARR forcing produced high-biased chlorophyll, resulting from low-biased wind speed and spring mixed layer depth. Simulated mussel filter feeding strongly reduced phytoplankton abundance when the water column was mixed to the bottom, but had little effect during periods of summer and winter stratification. These model simulations highlight the sensitivity of both phytoplankton growth and the impact of profundal quagga mussel filter-feeding to vertical mixing and stratification, which in turn is controlled by meteorological conditions.
ROWE, M.D., D.R. Obenour, T.F. Nalepa, H.A. VANDERPLOEG, F. Yousef, and W.C. Kerfoot. Mapping the spatial distribution of the biomass and filter-feeding effect of invasive dreissenid mussels on the winter-spring phytoplankton bloom in Lake Michigan. Freshwater Biology:15 (DOI:10.1111/fwb.12653) (2015).
1. The effects of the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriformis bugensis (quagga mussel) on aquatic ecosystems, including Lake Michigan, are a topic of current interest to scientists and resource managers. We hypothesized that the winter–spring phytoplankton bloom in Lake Michigan is reduced at locations where the fraction of the water column cleared per day by Dreissena filter feeding approached the net growth rate of phytoplankton, when the water column was not stratified. To test this hypothesis, we compared the spatial distribution of Dreissena filter-feeding intensity (determined from geostatistical modelling) to the spatial distribution of chlorophyll (determined from satellite remote sensing). 2. To map the spatial distribution of Dreissena biomass and filter-feeding intensity, we developed a geostatistical model based on point observations of mussel biomass measured in Lake Michigan in 1994/1995, 2000, 2005 and 2010. The model provided fine-scale estimates of the spatial distribution of biomass for the survey years and provided estimates, with their uncertainty, of total biomass lakewide and within subregions. The approach outlined could be applied more generally to map the distribution of benthic biota in lakes from point observations. 3. Total biomass of Dreissena in Lake Michigan, estimated from the geostatistical model, increased significantly over each five-year period. The total biomass in units of 106 kg ash-free dry mass (AFDM) (with 90% confidence interval) was 6 (4–8) in 1994/1995, 18 (14–23) in 2000, 408 (338–485) in 2005 and 610 (547–680) in 2010. From 1994/1995 to 2005, increases were observed in all regions of the lake (northern, central and southern) and in all depth zones (<30, 30–50, 50–90 and >90). However, from 2005 to 2010, for depths of <50 m, biomass declined in the northern region, remained constant in the central region and increased in the southern region; biomass continued to increase in all three lake regions for depths >50 m. 4. The filter-feeding intensity of Dreissena exceeded the benchmark spring phytoplankton growth rate of 0.06 day _1 in 2005 for depths <50 m (lakewide). In 2010, the filter-feeding impact exceeded 0.06 day _1 within depths <90 m (lakewide), which greatly increased the spatial area affected relative to 2005. A regression analysis indicated a significant relationship between the reduction in satellite-derived chlorophyll concentration (pre-D. r. bugensis period to post-D. r. bugensis period) and spatially co-located filter-feeding intensity (fraction of water column cleared per day) during periods when the water column was not stratified (December to April).
Sharma, S., (among 72 others), and G.A. LESHKEVICH. A global database of lake surface temperatures collected by in situ and satellite methods from 1985-2009. Nature Scientific Data:19 pp. (DOI:10.1038/sdata/2015.8) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150016.pdf
Global environmental change has influenced lake surface temperatures, a key driver of ecosystem structure and function. Recent studies have suggested significant warming of water temperatures in individual lakes across many different regions around the world. However, the spatial and temporal coherence associated with the magnitude of these trends remains unclear. Thus, a global data set of water temperature is required to understand and synthesize global, long-term trends in surface water temperatures of inland bodies of water. We assembled a database of summer lake surface temperatures for 291 lakes collected in situ and/or by satellites for the period 1985–2009. In addition, corresponding climatic drivers (air temperatures, solar radiation, and cloud cover) and geomorphometric characteristics (latitude, longitude, elevation, lake surface area, maximum depth, mean depth, and volume) that influence lake surface temperatures were compiled for each lake. This unique dataset offers an invaluable baseline perspective on global-scale lake thermal conditions as environmental change continues.
Smith, S.D.P., P.B. McIntyre, B.S. Halpern, R.M. Cooke, A.L. Marino, G.L. Boyer, A. Buchsbaum, G.A. BURTON, L.M. Campbell, J.J.H. Ciborowski, P.J. Doran, D.M. Infante, L.B. Johnson, J.G. Read, J.B. Rose, E.S. RUTHERFORD, A.D. Steinman, and J.D. Allan. Rating impacts in a multi-stressor world: A quantitative assessment of 50 stressors affecting the Great Lakes. Ecological Applications 25(3):717-728 (DOI:10.1890/14-0366.1) (2015).
Ecosystems often experience multiple environmental stressors simultaneously that can differ widely in their pathways and strengths of impact. Differences in the relative impact of environmental stressors can guide restoration and management prioritization, but few studies have empirically assessed a comprehensive suite of stressors acting on a given ecosystem. To fill this gap in the Laurentian Great Lakes, where considerable restoration investments are currently underway, we used expert elicitation via a detailed online survey to develop ratings of the relative impacts of 50 potential stressors. Highlighting the multiplicity of stressors in this system, experts assessed all 50 stressors as having some impact on ecosystem condition, but ratings differed greatly among stressors. Individual stressors related to invasive and nuisance species (e.g., dreissenid mussels and ballast invasion risk) and climate change were assessed as having the greatest potential impacts. These results mark a shift away from the longstanding emphasis on nonpoint phosphorus and persistent bioaccumulative toxic substances in the Great Lakes. Differences in impact ratings among lakes and ecosystem zones were weak, and experts exhibited surprisingly high levels of agreement on the relative impacts of most stressors. Our results provide a basin-wide, quantitative summary of expert opinion on the present-day influence of all major Great Lakes stressors. The resulting ratings can facilitate prioritizing stressors to achieve management objectives in a given location, as well as providing a baseline for future stressor impact assessments in the Great Lakes and elsewhere.
Soranno, P.A., (among 23 others), and C.A. STOW. Building a multi-scaled geospatial temporal ecology database from disparate data sources: Fostering open science through data reuse. GigaScience 4(28):15 pp. (DOI:10.1186/s13742-015-0067-4) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150032.pdf
Although there are considerable site-based data for individual or groups of ecosystems, these datasets are widely scattered, have different data formats and conventions, and often have limited accessibility. At the broader scale, national datasets exist for a large number of geospatial features of land, water, and air that are needed to fully understand variation among these ecosystems. However, such datasets originate from different sources and have different spatial and temporal resolutions. By taking an open-science perspective and by combining site-based ecosystem datasets and national geospatial datasets, science gains the ability to ask important research questions related to grand environmental challenges that operate at broad scales. Documentation of such complicated database integration efforts, through peer-reviewed papers, is recommended to foster reproducibility and future use of the integrated database. Here, we describe the major steps, challenges, and considerations in building an integrated database of lake ecosystems, called LAGOS (LAke multi-scaled GeOSpatial and temporal database), that was developed at the sub-continental study extent of 17 US states (1,800,000 km2). LAGOS includes two modules: LAGOSGEO, with geospatial data on every lake with surface area larger than 4 ha in the study extent (~50,000 lakes), including climate, atmospheric deposition, land use/cover, hydrology, geology, and topography measured across a range of spatial and temporal extents; and LAGOSLIMNO, with lake water quality data compiled from ~100 individual datasets for a subset of lakes in the study extent (~10,000 lakes). Procedures for the integration of datasets included: creating a flexible database design; authoring and integrating metadata; documenting data provenance; quantifying spatial measures of geographic data; quality-controlling integrated and derived data; and extensively documenting the database. Our procedures make a large, complex, and integrated database reproducible and extensible, allowing users to ask new research questions with the existing database or through the addition of new data. The largest challenge of this task was the heterogeneity of the data, formats, and metadata. Many steps of data integration need manual input from experts in diverse fields, requiring close collaboration.
STOW, C.A. The need for sustained, long-term phosphorus modeling in the Great Lakes. Journal of Great Lakes Research 41(2):315-316 (DOI:10.1016/j.jglr.2015.03.001) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150010.pdf
The 1978 Great Lakes Water Quality Agreement contained annual phosphorus load targets for each of the Great Lakes and larger bays. These targets were developed to combat eutrophication symptoms that resulted in the impairment of what we now refer to as ecosystem services. The targets were derived from several models of differing complexity and spatiotemporal resolution. As an ensemble those models reflected the knowledge and technology of the time. In the 1970s, this approach was new and somewhat of an experiment. Ecosystem management at this scale was unprecedented and the result was uncertain. However, it put the Great Lakes region at the forefront of innovative environmental management, and the approach has been widely copied in what we now refer to as Total Maximum Daily Loads. In the 1980s, there were signs that the experiment was working as eutrophication symptoms began to diminish. Unfortunately, these improvements were interpreted to indicate that the job was done. We declared success and moved on to other concerns such as toxic chemicals. The models were largely shelved, and the monitoring efforts supporting them were substantially reduced. At the time, such actions probably seemed sensible. Our view was that the lakes were fixed, and we could move on to other important concerns. This outlook was not confined to the Great Lakes community, but reflected the broader prevailing wisdom of the time.
STOW, C.A., Y.K. Cha, L.T. Johnson, R. Confesor, and R.P. Richards. Long-term and seasonal trend decomposition of Maumee River nutrient inputs to western Lake Erie. Environmental Science & Technology 49:3392-3400 (DOI:10.1021/es5062648) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150009.pdf
Cyanobacterial blooms in western Lake Erie have recently garnered widespread attention. Current evidence indicates that a major source of the nutrients that fuel these blooms is the Maumee River. We applied a seasonal trend decomposition technique to examine long-term and seasonal changes in Maumee River discharge and nutrient concentrations and loads. Our results indicate similar long-term increases in both regional precipitation and Maumee River discharge (1975−2013), although changes in the seasonal cycles are less pronounced. Total and dissolved phosphorus concentrations declined from the 1970s into the 1990s; since then, total phosphorus concentrations have been relatively stable, while dissolved phosphorus concentrations have increased. However, both total and dissolved phosphorus loads have increased since the 1990s because of the Maumee River discharge increases. Total nitrogen and nitrate concentrations and loads exhibited patterns that were almost the reverse of those of phosphorus, with increases into the 1990s and decreases since then. Seasonal changes in concentrations and loads were also apparent with increases since approximately 1990 in March phosphorus concentrations and loads. These documented changes in phosphorus, nitrogen, and suspended solids likely reflect changing land-use practices. Knowledge of these patterns should facilitate efforts to better manage ongoing eutrophication problems in western Lake Erie.
VANDERPLOEG, H.A., D.B. Bunnell, H.J. Carrick, and T.O. Hook. Complex interactions in Lake Michigan's rapidly changing ecosystem. Journal of Great Lakes Research 41 (Supplement 3):6 (DOI:10.1016/j.jglr.2015.11.001) (2015).
Over the past 30 years, Lake Michigan's food web has been in a constant state of transition (Vanderploeg et al., 2002, 2012; Madenjian et al., 2002; in this issue), and it is likely that this emerging system has not yet reached a steady state. The proliferation of invasive species at multiple trophic levels (zooplankton, mussels, fish), coupled with the success of a nutrient abatement program that has delivered long-term reductions in nutrient inputs, have together contributed to a series of systemic changes to the Lake Michigan ecosystem (e.g., novel trophic interactions, reengineered nutrient cycling, altered physical habitat, shift from pelagic productivity to enhanced benthic production, and nuisance algal blooms nearshore). Our current understanding and potential future forecasting of ecosystem-wide consequences of such transitions are dependent on describing and understanding changes in the food web in time and space (i.e., horizontal and vertical), variation of key food web components and linkages with physical habitat, and nutrient cycling. Given that other Laurentian Great Lakes share key members of the Lake Michigan food web as well as changing nutrient and climate dynamics, understanding gleaned from this special issue is highly relevant across the basin, especially in Lakes Huron and Ontario.
Wang, D., Y. Yang, J. WANG, K. Mizobata, and X. BAI. A modeling study of the effects of river runoff, tides, and surface wind-wave mixing on the eastern and western Hainan upwelling systems of the South China Sea, China. Ocean Dynamics 65:24 pp. (DOI:10.1007/s10236-015-0857-3) (2015).
This study investigates the variation of eastern Hainan (or Qiongdong) and western Hainan upwelling systems during the East Asia summer monsoon (EASM) season using a state-of-the-art finite-volume coastal model and reveals the impacts of tidal mixing, surface wind-wave mixing, and river runoff on the Hainan upwellings in terms of the spatial and temporal variations, intensification, and vertical structure. It is found that (1) river runoff, a stabilizer of the water column, suppresses the upwelling beneath it from reaching the surface, although strong upwelling still occurs in the lower layer of the water column; (2) tidal mixing, a mechanism of forming bottom mixed layer, promotes upwelling, leading to strengthening of the upwelling; (3) surface wind-wave mixing, a major mechanism for formation of the upper mixed layer and a sharp thermocline, inhibits the upwelling from crossing the thermocline to reach the surface; and (4) unlike the east coast upwelling, the upwelling on the west coast is tidally induced.
Wang, L., C.M. Riseng, L.A. Mason, K.E. Wehrly, E.S. RUTHERFORD, J.E. McKenna, C. Castiglione, L.B. Johnson, D.M. Infante, S.P. Sowa, M. Robertson, J.S. Schaeffer, M. Khoury, J. Gaiot, T. Hollenhorst, C. Brooks, and M. Coscarelli. A spatial classification and database for management, research, and policy making: The Great Lakes Aquatic Habitat Framework. Journal of Great Lakes Research 41(2):584-596 (DOI:10.1016/j.jglr.2015.03.017) (2015).
Managing the world's largest and most complex freshwater ecosystem, the Laurentian Great Lakes, requires a spatially hierarchical basin-wide database of ecological and socioeconomic information that is comparable across the region. To meet such a need, we developed a spatial classification framework and database — Great Lakes Aquatic Habitat Framework (GLAHF). GLAHF consists of catchments, coastal terrestrial, coastal margin, nearshore, and offshore zones that encompass the entire Great Lakes Basin. The catchments captured in the database as river pour points or coastline segments are attributed with data known to influence physicochemical and biological characteristics of the lakes from the catchments. The coastal terrestrial zone consists of 30-m grid cells attributed with data from the terrestrial region that has direct connection with the lakes. The coastal margin and nearshore zones consist of 30-m grid cells attributed with data describing the coastline conditions, coastal human disturbances, and moderately to highly variable physicochemical and biological characteristics. The offshore zone consists of 1.8-km grid cells attributed with data that are spatially less variable compared with the other aquatic zones. These spatial classification zones and their associated data are nested within lake subbasins and political boundaries and allow the synthesis of information from grid cells to classification zones, within and among political boundaries, lake sub-basins, Great Lakes, or within the entire Great Lakes Basin. This spatially structured database could help the development of basin-wide management plans, prioritize locations for funding and specific management actions, track protection and restoration progress, and conduct research for science-based decision making.
Wynne, T.T., T.W. DAVIS, R. Kelty, E.J. ANDERSON, and S.J. JOSHI. NOAA forecasts and monitors blooms of toxic cyanobacteria in Lake Erie. In Clear Waters. New York Water Environment Association, Inc., Syracuse, NY, 21-23 pp. (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150041.pdf
Blooms of cyanobacteria (commonly referred to as bluegreen algae) have been reported in Lake Erie as far back as the 1960s and 1970s. These blooms were nearly eliminated in Lake Erie by phosphorus abatement strategies in the 1970s that were part of the Great Lakes Water Quality Agreement, but re-emerged as a major water quality issue in the mid-1990s. The re-emergence of the blooms has been hypothesized to be a result of increases in agricultural pollution (nitrogen and phosphorus) into western Lake Erie. The role of the colonization of the invasive dreissenid mussels (a collective term for three similar mussel species) in promoting the re-emergence of the blooms is also being investigated.
XIAO, C., and Y. Zhang. Projected changes of wintertime synoptic-scale transient eddy activities in the East Asian eddy-driven jet from CMIP5 experiments. Geophysical Research Letters 42(14):6008-6013 (DOI:10.1002/2015GL064641) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150040.pdf
The wintertime East Asian eddy-driven jet (EAEJ) responding to climate change in the 21st century is studied using model outputs from the Coupled Model Intercomparison Project phase 5 (CMIP5). Compared to the location displacement in oceanic eddy-driven jets, the magnitude change of synoptic-scale transient eddy activities, measured by eddy kinetic energy (EKE), is a more striking feature in EAEJ. An intensified EKE is projected unanimously by CMIP5 models, suggesting that potential strong winter storm events are likely to happen in East Asian midlatitude in a warming climate. The future change of EKE in EAEJ can be understood in terms of growing baroclinicity wave. The upper level EKE is highly correlated to the low-level static stability, Brunt-Väisälä frequency (BVF). CMIP5 models generally project an intensified upper level EKE with a reduced low-level BVF (ΔEKE_ΔBVF). Meanwhile, the enhancement of EKE is also constrained by its historical state (ΔEKE _EKE). Intermodel variabilities among CMIP5 models reveal a similar but weaker relationship between ΔBVF (or EKE) and ΔEKE, indicating relatively large model diversities and independencies among CMIP5 models.
Zhang, L., S. Wang, C. He, K. Shang, L. Meng, X. Li, and B.M. LOFGREN. A new method for instant correction of numerical weather prediction products in China. Science China - Earth Sciences 58(2):231-244 (DOI:10.1007/s11430-014-4957-6) (2015).
This paper presents a new correction method, “instant correction method (ICM)”, to improve the accuracy of numerical prediction products (NPP) and provide weather variables at grid cells. The ICM makes use of the continuity in time of the forecast errors at different forecast times to improve the accuracy of large scale NPP. To apply the ICM in China, an ensemble correction scheme is designed to correct the T213 NPP (the most popular NPP in China) through different statistical methods. The corrected T213 NPP (ICM T213 NPP) are evaluated by four popular indices: Correlation coefficient, climate anomalies correlation coefficient, root-mean-square-errors (RMSE), and confidence intervals (CI). The results show that the ICM T213 NPP are more accurate than the original T213 NPP in both the training period (2003–2008) and the validation period (2009–2010). Applications in China over the past three years indicate that the ICM is simple, fast, and reliable. Because of its low computing cost, end users in need of more accurate short-range weather forecasts around China can benefit greatly from the method.
Zhou, Y., A.M. Michalak, D. BELETSKY, Y.R. Rao, and R.P. Richards. Record-breaking Lake Erie hypoxia during 2012 drought. Environmental Science & Technology 49(2):800-807 (DOI:10.1021/es503981n) (2015).
Hypoxia has been observed in the central basin of Lake Erie for decades. To understand the impact of various controlling factors, we analyze a record of hypoxic extents for Lake Erie for 1985−2012 and develop a parsimonious model of their interannual variability. We find that the 2012 North American drought and accompanying low tributary discharge was associated with a record-breaking hypoxic event in Lake Erie, whereas a record-setting harmful algal bloom in 2011 was likely associated with only mild hypoxia. River discharge and the timing of nutrient input therefore impact western basin bloom growth and central basin oxygen demand in distinct ways that merit further investigation. Overall, April to June tributary discharge, May to July soluble reactive phosphorus loading, July wind stress, and June northwesterly wind duration explain 82% of the interannual variability of hypoxia, and discharge alone explains 39%, indicating that meteorological factors need to be considered in the development of nutrient management strategies, especially as both extreme precipitation events and droughts become more frequent under a changing climate.
Zhu, X., G. LIU, J. WANG, H. Wang, X. Bao, and W. Hu. A numerical study on the relationships of the variations of volume transport around the China Seas. Journal of Marine Systems 145:15-36 (DOI:10.1016/j.jmarsys.2014.12.003) (2015).
Three dimensional oceanic circulations in the North Pacific Ocean are simulated using the Regional OceanModel System (ROMS). The model very well reproduces the main oceanic circulation patterns and the hydrodynamic structures in the North Pacific Ocean, especially in the China seas. Eight transects around the China seas are selected to analyze volume transport and their relationships. The simulated mean volume transport and their standard deviations are in good agreement with previous studies and observations in the Taiwan Strait (TWS, 1.79 ± 0.96 Sv, 1 Sv 106 m3/s), East of Taiwan (PCM, 20.03 ± 5.19 Sv), Tokara Strait (TKS, 19.22 ± 3.22 Sv), Tsushima Strait (TUS, 2.14 ± 0.47 Sv), Luzon Strait (LUS, 4.57 ± 4.13 Sv), Karimata Strait (KMS, 1.28 ± 0.65 Sv), East of Luzon Island (ELI, 13.93 ± 5.31 Sv), and 137°E across the North Equatorial Current from 10°N to 20°N (137E, 44.0 ± 9.90 Sv). Three kinds of time scale variations (seasonal, sub-seasonal, intra-seasonal) were found in the volume transport through these transects with over the 95% significance level. The power spectrum density of the seasonal variation was almost one order of magnitude larger than the others for transects around the China seas. Coherency relationships among the volume transport through transects were analyzed. The results indicate that the seasonal time scale variations in volume transport around the China seas were dominated by the monsoon winds, but the Kuroshio along its pathway was relatively stable with small seasonal variation; the sub-seasonal time scale variations were associated with strong monsoon reversal winds; and the intra-seasonal variations were complex and weak, associating with local small scale winds and mesoscale eddy activities along the Kuroshio.
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