January 2012 - December 2012
|Capitalized names represent GLERL authors.|
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ANDERSON, E.J., and D.J. SCHWAB. Contaminant transport and spill reference tables for the St. Clair River. Marine Technology Society Journal 46(5):34-47 (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120035.pdf
The goal of this work is to calibrate a real-time hydrodynamic model for spill tracking in the St. Clair River and to provide decision makers with information for response planning and in the event of a spill. In order to provide experimental validation data, three dye releases were carried out to simulate movement of a potential contaminant in the river. Measurements of dye concentration were used to provide estimates of lateral and vertical mixing as well as travel time of the dye cloud. Model simulations were able to recreate the dye movement and concentrations with model-estimated arrival times within 14 min of the observed plume arrival times and concentrations within 0.005 normalized concentration units of the observed concentrations (which ranged from 0.06 to 0.004). Following model calibration, a set of spill scenarios was chosen to encompass the types and locations of spills commonly experienced in the St. Clair River. These spill scenarios were then simulated with the HECWFS model to predict transport characteristics such as plume leading edge travel time, duration, concentration, and cross-channel mixing. Results from the scenarios were compiled into reference tables in which spill characteristics are listed at several downstream transects. These spill reference tables provide water intake operators with information before the event of a spill, enabling decision makers to plan for potential or common spills as well as providing a quick reference library that can be accessed immediately after a spill is detected to aid in mitigating the effects on drinking water supply.
BAI, X., and J. WANG. Atmospheric teleconnetion patterns associated with severe and mild ice cover in the Great Lakes, 1963-2011. Water Quality Research Journal of Canada, Special Issue on Physical Processes in Natural Waters 47(3-4):421-435 (DOI:10.2166/wqrjc.2012.009) (2012).
Atmospheric teleconnection circulation patterns associated with severe and mild ice cover over the Great Lakes are investigated using the composite analysis of lake ice data and National Center of Environmental Prediction (NCEP) reanalysis data for the period 1963–2011. The teleconnection pattern associated with the severe ice cover is the combination of a negative North Atlantic Oscillation (NAO) or Arctic Oscillation (AO) and negative phase of Pacific/North America (PNA) pattern, while the pattern associated with the mild ice cover is the combination of a positive PNA (or an El Niño) and a positive phase of the NAO/AO. These two extreme ice conditions are associated with the North American ridge–trough variations. The intensified ridge–trough system produces a strong northwest-to-southeast tilted ridge and trough and increases the anomalous northwesterly wind, advecting cold, dry Arctic air to the Great Lakes. The weakened ridge–trough system produces a flattened ridge and trough, and promotes a climatological westerly wind, advecting warm, dry air from western North America to the Great Lakes. Although ice cover for all the individual lakes responds roughly linearly and symmetrically to both phases of the NAO/AO, and roughly nonlinearly and asymmetrically to El Niño and La Niña events, the overall ice cover response to individual NAO/AO or Niño3.4 index is not statistically significant. The combined NAO/AO and Niño3.4 indices can be used to reliably project severe ice cover during the simultaneous –NAO/AO and La Niña events, and mild ice cover during the simultaneous þNAO/AO and El Niño events.
BAI, X., J. WANG, C.E. SELLINGER, A.H. CLITES, and R.A. ASSEL. Interannual variability of Great Lakes ice cover and its relationship to NAO and ENSO. Journal of Geophysical Research 117(C03002):25 pp. (DOI:10.1029/2010JC006932) (2012).
The impacts of North Atlantic Oscillation (NAO) and El Niño–Southern Oscillation (ENSO) on Great Lakes ice cover were investigated using lake ice observations for winters 1963–2010 and National Centers for Environmental Prediction reanalysis data. It is found that both NAO and ENSO have impacts on Great Lakes ice cover. The Great Lakes tend to have lower (higher) ice cover during the positive (negative) NAO. El Niño events are often associated with lower ice cover. The influence of La Niña on Great Lakes ice cover is intensity-dependent: strong (weak ) La Niña events are often associated with lower (higher) ice cover. The interference of impacts of ENSO and NAO complicates the relationship between ice cover and either of them. The nonlinear effects of ENSO on Great Lakes ice cover are important in addition to NAO effects. The correlation coefficient between the quadratic Nino3.4 index and ice cover (!0.48) becomes significant at the 99% confidence level. The nonlinear response of Great Lakes ice cover to ENSO is mainly due to the phase shift of the teleconnection patterns during the opposite phases of ENSO. Multiple-variable nonlinear regression models were developed for ice coverage. Using the quadratic Nino3.4 index instead of the index itself can significantly improve the prediction of Great Lakes ice cover (the correlation between the modeled and observed increases from 0.35 to 0.51). Including the interactive term NAO Nino3.42 further improves the prediction skill (the correlation increases from 0.51 to 0.59). The analysis is also applied to individual lakes. The model for Lake Michigan has the highest prediction skill, while Lake Erie has the smallest skill.
BELETSKY, D., N. HAWLEY, Y. Rao, H.A. VANDERPLOEG, R. BELETSKY, D.J. SCHWAB, and S.A. RUBERG. Summer thermal structure and anticyclonic circulation of Lake Erie. Geophysical Research Letters 39:L06605 (DOI:10.1029/2012GL051002) (2012).
In most thermally stratified lakes, the summer thermocline has the shape of a “dome”, with a shallower depth offshore than nearshore. This configuration is accompanied by a lake-wide cyclonic circulation. Lake-wide observations of subsurface temperature in central Lake Erie revealed an atypical “depressed” or “bowl-shaped” thermocline in late summer, with a deeper thermocline in the middle of the lake and a shallower thermocline nearshore. Currents measured in the central basin when the bowl-shaped thermocline was observed were anticyclonic, forming a single basin-wide gyre. It is suggested that the unusual bowl-shaped thermocline is the result of Ekman pumping driven by anticyclonic vorticity in surface winds. The bowl-shaped thermocline can lead to greater hypoxia in bottom waters and negative effects on biota by reducing the hypolimnetic volume.
Biddanda, B.A., S.C. Nold, G.J. Dick, S.T. Kendall, J.H. Vail, S.A. RUBERG, and C.M. Green. Rock, water, microbes: Underwater sinkholes in Lake Huron are habitats for ancient microbial life. Nature Education Knowledge 3(3):5 (2012). https://www.nature.com/scitable/knowledge/library/rock-water-microbes-underwater-sinkholes-in-lake-25851285
Time, water, and geologic forces have converged to create underwater sinkholes where oxygen poor and sulfur-rich groundwater support prolific microbial mats resembling life on early Earth. Imagine being able to look back into the distant past through a "time- portal." Wouldn't it be fascinating to see life as it was 2.5 billion years ago (bya) in the shallow seas of the early Earth? These were harsh times when there was no available oxygen, and life was entirely composed of microorganisms. Well, scientists have discovered such a place within collapsed depressions along the lake floor in what are called submerged sinkholes in Lake Huron, one of the five Great lakes located in North America. The sinkholes' inhabitants - mostly microbes - are providing us a glimpse of what early life on Earth might have been like and how it might have transformed the planet. Here, colorful microbial mats with bubbling gasses have been discovered which are not found anywhere else in the Great lakes, and are known to occur in just a few other places on Earth. Since 2002, scientists interested in the geology, hydrology, chemistry and biology of sinkholes have explored these habitats. Explorations using research vessels, remotely operated vehicles (ROVs), scuba divers, underwater sensors. metabolic chambers, sediment corers, as well as laboratory-based studies are revealing a fascinating working picture of this unique ecosystem.
Bunnell, D.B., K. Keeler, E. Puchala, B.M. Davis, and S.A. POTHOVEN. Comparing seasonal dynamics of the Lake Huron zooplankton community between 1983-1984 and 2007 and revisiting the impact of Bythotrephes planktivory. Journal of Great Lakes Research 38(3):451-462 (DOI:10.1016/j.jglr.2012.04.007) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120029.pdf
Zooplankton community composition can be influenced by lake productivity as well as planktivory by fish or invertebrates. Previous analyses based on long-term Lake Huron zooplankton data from August reported a shift in community composition between the 1980s and 2000s: proportional biomass of calanoid copepods increased while that of cyclopoid copepods and herbivorous cladocerans decreased. Herein, we used seasonally collected data from Lake Huron in 1983–1984 and 2007 and reported similar shifts in proportional biomass. We also used a series of generalized additive models to explore differences in seasonal abundance by species and found that all three cyclopoid copepod species (Diacyclops thomasi, Mesocylops edax, Tropocyclops prasinus mexicanus) exhibited higher abundance in 1983–1984 than in 2007. Surprisingly, only one (Epischura lacustris) of seven calanoid species exhibited higher abundance in 2007. The results for cladocerans were also mixed with Bosmina spp. exhibiting higher abundance in 1983–1984, while Daphnia galeata mendotae reached a higher level of abundance in 2007. We used a subset of the 2007 data to estimate not only the vertical distribution of Bythotrephes longimanus and their prey, but also the consumption by Bythotrephes in the top 20 m of water. This epilimnetic layer was dominated by copepod copepodites and nauplii, and consumption either exceeded (Hammond Bay site) or equaled 65% (Detour site) of epilimnetic zooplankton production. The lack of spatial overlap between Bythotrephes and herbivorous cladocerans and cyclopoid copepod prey casts doubt on the hypothesis that Bythotrephes planktivory was the primary driver underlying the community composition changes in the 2000s.
CHA, Y.K., C.A. STOW, and E. Bernhardt. Impact of dreissenid mussel invasions on chlorophyll and total phosphorus in 25 lakes in the USA. Freshwater Biology:15 pp. (DOI:10.1111/fwb.12050) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120039.pdf
1. Invasions of zebra and quagga mussels have had long-term, large-scale impacts on lake ecosystems in the USA as characterised by high abundance, broad-scale spread and effective adaption to new environmental conditions. Due to their high filtering capacity, decreases in chlorophyll a (Chl) and total phosphorus (TP) concentrations have been reported in many affected lakes. 2. In 25 US lakes, we analysed the effects of dreissenid invasions on changes in Chl and TP concentrations, measured as the probability of a concentration decrease in the post-invasion period and changes in Chl–TP relationships using Bayesian hierarchical regressions. We also examined whether changes in Chl and TP concentrations and in the Chl–TP relationship differed according to lake hydromorphology, such as mean depth or mixing status (mixed versus stratified lakes). 3. Our results showed that dreissenid invasions were often, but not always, associated with subsequent TP and Chl declines. Dreissenid effects on Chl and TP may be influenced by lake thermal structure. Decreases in Chl and TP were consistently found in mixed lakes where benthic–pelagic coupling is tight, while the effects were less predictable in stratified lakes. Within stratified lakes, Chl and TP reductions were more clearly discernible in deeper lakes with long water residence times. 4. Regression results demonstrated that a joint increase in slope and decrease in intercept and a tighter correlation of the Chl–TP relationship were likely to occur in dreissenid-invaded lakes; this does not support the idea of a shift from bottom-up to top-down control of primary production. These results have important implications for management, suggesting that a relaxation of TP standards would be unwarranted. 5. Across lakes, the slope of the Chl–TP relationship for mixed lakes was substantially higher than that for stratified lakes before mussel invasion, indicating an important role of light in limiting primary production. The slope differences between mixed and stratified lakes decreased in the post-invasion period, possibly because mussel filtration results in a relaxation of light limitation that is more pronounced in deeper, stratified lakes.
Choi, J., C.D. Troy, T.C. Hsieh, N. HAWLEY, and M.J. McCORMICK. A year of internal poincare waves in southern lake Michigan. Journal of Geophysical Research 117(C07014):12 pp. (DOI:10.1029/2012JC007984) (2012).
A unique set of full year, deep water observations from the middle of Lake Michigan’s southern basin are analyzed to quantify the seasonal variability of the dominant near-inertial internal Poincaré wave. At this mid-lake location, the Poincaré wave is seen to describe more than 80% of the observed surface current variability for much of the year, with characteristic near-inertial frequency and clockwise-rotating velocities. The dominance of the near-inertial seiche on the flow decreases with depth. The wave persists during the “stratified period,” roughly May through late December, and is supported by as few as 1–2 degrees of thermal stratification over 150 m; only after complete water column mixing does the wave go dormant for January through April. The strongest Poincaré wave activity is seen to correspond to the period of strongest summer thermal stratification (August), in spite of the relatively weak winds at this time. A simple inertial slab model optimized with linear friction is shown to capture the seasonal variability of the near-inertial energy at this location reasonably well. The vertical structure of the wave shows good agreement with that calculated with a standard normal modes formulation, which is in turn used to characterize the potential shear and mixing caused by the wave. Late-spring and summer events of elevated Poincaré wave activity are shown to generate sufficiently strong shear with persistent periods of sub-1 Richardson numbers within the thermocline, suggesting that the near-inertial seiche is likely generating thermocline instabilities in the lake’s interior.
Fortin, V., and A.D. GRONEWOLD. Water balance of the Laurentian Great Lakes. In Encyclopedia of Lakes and Reservoirs. L Bengtsson, R.W. Herschy, and R.W. Fairbridge (eds.). Springer, Encyclopedia of Earth Sciences Series, 864-868 pp. (DOI:10.1007/978-1-4020-4410-6_268) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120030.pdf
Surface water elevation dynamics of the Laurentian Great Lakes exhibit long-term persistence on decadal time scales, and the changes in surface water elevation over these time scales are driven mainly by climate dynamics. Understanding Great Lakes water elevation dynamics on shorter time scales (such as monthly and annual scales) is commonly based on a cumulative assessment of the individual components of the net supply of water (i.e., precipitation, evaporation, and runoff) within the Great Lakes basin.
FUJISAKI, A., J. WANG, H. HU, D.J. SCHWAB, N. HAWLEY, and R. Yerubandi. A modeling study of ice-water processes for Lake Erie using coupled ice-circulation models. Journal of Great Lakes Research 38(4):15 pp. (DOI:10.1016/j.jglr.2012.09.021) (2012). https://dx.doi.org/10.1016/j.jglr.2012.09.021
A hydrodynamic model that includes ice processes and is optimized for parallel processing was configured for Lake Erie in order to study the ice–water coupling processes in the lake. A hindcast from April 2003 to December 2004 with hourly atmospheric forcing was conducted. The model reproduced the seasonal variation of ice cover, but the development of ice extent in January and its decay inMarch somewhat preceded the observations. Modeled lake circulation in ice-free seasons is consistent with previous studies for Lake Erie. Thermal structure of the lake was reasonably comparable to both satellite-derived observations and in-situ measurements, with mean differences ranging from−2 °C to 4 °C, depending on the season. The impacts of ice–water stress coupling and basal melting of ice were examined based on numerical experiments. The results show that: 1) ice–water stress coupling significantly dampens the subjacent lake circulation in winter due to packed ice cover that slows down the surface water, and 2) basal melting of ice contributes to widespread ice cover in the lake. The demonstrated model validity could lead to further studies of ice–water processes in the lake, including interannual variation and impacts on ecosystems.
Goto, D., K. Lindelof, D.L. FANSLOW, S.A. Ludsin, S.A. POTHOVEN, J.J. Roberts, H.A. VANDERPLOEG, A.E. Wilson, and T.O. Hook. Indirect consequence of hypolimnetic hypoxia on zooplaknton growth in a large eutrophic lake. Aquatic Biology 16:217-227 (DOI:10.3354/ab00442) (2012).
Diel vertical migration (DVM) of some zooplankters in eutrophic lakes is often compressed during peak hypoxia. To better understand the indirect consequences of seasonal hypolimnetic hypoxia, we integrated laboratory-based experimental and field-based observational approaches to quantify how compressed DVM can affect growth of a cladoceran, Daphnia mendotae, in central Lake Erie, North America. To evaluate hypoxia tolerance of D. mendotae, we conducted a survivorship experiment with varying dissolved oxygen concentrations, which demonstrated high sensisity of D. mendotae to hypoxia (≤ mg O2 l-1), supporting the field oservations of their behavioral avoidance of the hypoxic hypolimnion. To investigate the effect of temporary changes in habitat conditions associated with the compressed CVM, we quantified the grwoth of D. mendotae, using a 3 (food quantity) x 2 (temperature) factorial design laboratory experiment. Neither food quantity nor temperature affected short-term growth in body length of D. mendotae. However, D. mendotae RNA content (an index of short-term condition) decreased under starvation indicating an immediate response of short-term feeding on condition. We further evaluated the effect of hypoxia-induced upward shifts in vertical distribution by quantifying the RNA content of D. mendotae from central Lake Erie before and during peak hypoxia. Despite high temperature and food quantity in the upper water column, RNA content in field-collected D. mendotae remained low during peak hypoxia. Furthermore, D. mendotae collected during peak hypoxia consisted of only small-bodied (<~ 1.25 mm individuals, suggesting that behavioral avoidance of the hypoxic hypolimnion may also have indirect fitness costs.
Greene, C.H., B.C. Monger, L.P. McGarry, M.D. Connelly, N.R. Schnepf, A.J. Pershing, I.M. Belkin, P.S. Fratantoni, D.G. Mountain, R.S. Pickart, R. Ji, J.J. Bisagni, C. Chen, S.M.A. Hakkinen, D.B. Haidvogel, J. WANG, E. Head, P. Smith, and A. Conversi. Recent arctic climate change and its remote forcing of northwest Atlantic shelf ecosystems. Oceanography 6 pp. (DOI:doi.org/10.5670/oceanog.2012.64) (2012).
During recent decades, historically unprecedented changes have been observed in the Arctic as climate warming has increased precipitation, river discharge, and glacial as well as sea-ice melting. Additionally, shifts in the Arctic’s atmospheric pressure field have altered surface winds, ocean circulation, and freshwater storage in the Beaufort Gyre. These processes have resulted in variable patterns of freshwater export from the Arctic Ocean, including the emergence of great salinity anomalies propagating throughout the North Atlantic. Here, we link these variable patterns of freshwater export from the Arctic Ocean to the regime shifts observed in Northwest Atlantic shelf ecosystems. Specifically, we hypothesize that the corresponding salinity anomalies, both negative and positive, alter the timing and extent of water-column stratification, thereby impacting the production and seasonal cycles of phytoplankton, zooplankton, and higher-trophic-level consumers. Should this hypothesis hold up to critical evaluation, it has the potential to fundamentally alter our current understanding of the processes forcing the dynamics of Northwest Atlantic shelf ecosystems.
GRONEWOLD, A.D., and V. Fortin. Advancing Great Lakes hydrological science through targeted binational collaborative research. Bulletin of the American Meteorological Society:1921-1925 (DOI:10.1175/BAMS-D-12-00006.1) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120040.pdf
As one of the Earth’s largest surface freshwater resources, the North American Laurentian Great Lakes are an ideal test bed for understanding water balance dynamics of large hydrologic systems and for establishing effective protocols for collaborative binational water resources and ecosystem services research. To leverage ongoing and future federal government research efforts in the Great Lakes region, representatives from the National Oceanic and Atmospheric Administration (NOAA), the Cooperative Institute for Limnology and Ecosystems Research (CILER), and Environment Canada (EC) convened a workshop on Great Lakes hydrological modeling with an emphasis on improving regional hydrological and hydrodynamic science.
GRONEWOLD, A.D., C.A. STOW, J.L. Crooks, and T.S. HUNTER. Quantifying parameter uncertainty and assessing the skill of exponential dispersion rainfall simulation models. International Journal of Climatology 32:12 pp. (DOI:10.1002/joc.3469) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120016.pdf
The exponential dispersion model (EDM) has been demonstrated as an effective tool for quantifying rainfall dynamics across monthly time scales by simultaneously modelling discrete and continuous variables in a single probability density function. Recent applications of the EDM have included development and implementation of statistical software packages for automatically conditioning model parameters on historical time series data. Here, we advance the application of the EDM through an analysis of rainfall records in the North American Laurentian Great Lakes by implementing the EDM in a Bayesian Markov chain Monte Carlo (MCMC) framework which explicitly acknowledges historic rainfall variability and reflects that variability through uncertainty and correlation in model parameters and simulated rainfall metrics. We find, through a novel probabilistic assessment of skill, that the EDM reproduces the magnitude, variability, and occurrence of daily rainfall, but does not fully capture temporal autocorrelation on a daily time scale. These findings have significant implications for the extent to which the EDM can serve as a tool for supporting regional climate assessments, for downscaling regional climate scenarios into local-scale rainfall time series simulations, and for assessing trends in the historical climate record.
Holman, K.D., A.D. GRONEWOLD, M. Notaro, and A. Zarrin. Improving historical precipitation estimates over the Lake Superior basin. Geophysical Research Letters 39(L03405):5 pp. (DOI:10.1029/2011GL050468) (2012).
Lake Superior, the northern-most of the Laurentian Great Lakes, is the largest (by surface area) freshwater lake on the planet. Due in part to its high water surface to land area ratio, over one-third of the Lake Superior basin water budget is derived from precipitation falling directly on the lake surface. For most of the Great Lakes (including Lake Superior), historical precipitation estimates extend back to the early 1880s, and are based primarily on land-based gauge measurements. While alternatives to gauge-based estimates have been explored, there is no clear history of applying regional climate models (RCMs) to improve historical over-lake precipitation estimates. To address this gap in regional research, and to advance the state-of-the-art in Great Lakes regional hydrological modeling, we compare 21 years of output (1980–2000) from an RCM to conventional gauge-based precipitation estimates for the same time period over the Lake Superior basin.We find that the RCM, unlike the gauge-based method, simulates realistic variations in over-lake atmospheric stability, which propagate into basin-wide precipitation estimates with a relatively low over-lake to over-land precipitation ratio in warm months (roughly 0.7 to 0.8 in June, July, and August) and a relatively high over-lake to overland precipitation ratio in cold months (roughly 1.3 to 1.4 in December and January), compared to gauge-based estimates. Our findings underscore a need to potentially update historical gauge-based precipitation estimates for large lake systems, including Lake Superior, and that RCMs appear to provide a robust and defensible basis for making those updates.
Johnston, G., A. Mailett, and G.A. LESHKEVICH. Helicopter GPR. GPR Technology 8(30):2 (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120032.pdf
The Canadian Coast Guard's Ice Operations Team, in collaboration with Environment Canada and NOAA/Great Lakes Environmental Research Laboratory (GLERL), measures ice thickness with GPR for ship navigation, prediction of spring breakup, and ice rescues. GPR is usually deployed on the ice surface and pulled by hand, snowmobile, or some other tow vehicle. Recently the team tested airborne deployment of their GPR system.
Kolasa, J., C.R. Allen, J. Sendzimir, and C.A. STOW. Predictions and retrodictions of the hierarchical representation of habitat in heterogeneous environments. Ecological Modelling:9 pp. (DOI:10.1016/j.ecolmodel.2012.03.030) (2012).
Interaction between habitat and species is central in ecology. Habitat structure may be conceived as being hierarchical, where larger, more diverse, portions or categories contain smaller, more homogeneous portions. When this conceptualization is combined with the observation that species have different abilities to relate to portions of the habitat that differ in their characteristics, a number of known patterns can be derived and new patterns hypothesized. We propose a quantitative form of this habitat–species relationship by considering species abundance to be a function of habitat specialization, habitat fragmentation, amount of habitat, and adult body mass. The model reproduces and explains patterns such as variation in rank–abundance curves, greater variation and extinction probabilities of habitat specialists, discontinuities in traits (abundance, ecological range, pattern of variation, body size) among species sharing a community or area, and triangular distribution of body sizes, among others. The model has affinities to Holling’s textural discontinuity hypothesis and metacommunity theory but differs from both by offering a more general perspective. In support of the model, we illustrate its general potential to capture and explain several empirical observations that historically have been treated independently.
Langseth, B.J., M. Roger, and H. ZHANG. Modeling species invasions in Ecopath with Ecosim: An evaluation using Laurentian Great Lakes models. Ecological Modelling 247:251-261 (DOI:10.1016/j.ecolmodel.2012.08.015) (2012). https://dx.doi.org/10.1016/j.ecolmodel.2012.08.015
Invasive species affect the structure and processes of ecosystems they invade. Invasive species have been particularly relevant to the Laurentian Great Lakes, where they have played a part in both historical and recent changes to Great Lakes food webs and the fisheries supported therein. There is increased interest in understanding the effects of ecosystem changes on fisheries within the Great Lakes, and ecosystem models provide an essential tool from which this understanding can take place. A commonly used model for exploring fisheries management questions within an ecosystem context is the Ecopath with Ecosim (EwE) modeling software. Incorporating invasive species into EwE models is a challenging process, and descriptions and comparisons of methods for modeling species invasions are lacking. We compared four methods for incorporating invasive species into EwE models for both Lake Huron and Lake Michigan based on the ability of each to reproduce patterns in observed data time series. The methods differed in whether invasive species biomass was forced in the model, the initial level of invasive species biomass at the beginning of time dynamic simulations, and the approach to cause invasive species biomass to increase at the time of invasion. The overall process of species invasion could be reproduced by all methods, but fits to observed time series varied among the methods and models considered. We recommend forcing invasive species biomass when model objectives are to understand ecosystem impacts in the past and when time series of invasive species biomass are available. Among methods where invasive species time series were not forced, mediating the strength of predator–prey interactions performed best for the Lake Huron model, but worse for the Lake Michigan model. Starting invasive species biomass at high values and then artificially removing biomass until the time of invasion performed well for both models, but was more complex than starting invasive species biomass at low values. In general, for understanding the effect of invasive species on future fisheries management actions, we recommend initiating invasive species biomass at low levels based on the greater simplicity and realism of the method compared to others.
LESHKEVICH, G.A., R.A. Shuchman, and M.J. Sayers. An operational algorithm to retrieve chlorophyll, DOC, and suspended minerals from satellite data of the Great Lakes. Proceedings, European Space Agency (ESA) 3rd MERIS/Sentinel-3 Symposium, Franscati, Italy, October 15-19, 2012. ESA-ESRIN, 4 pp. (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120036.pdfA set of algorithms have been developed for the five North American Great Lakes that utilized MERIS, MODIS, or SeaWIFS satellite data to estimate chlorophyll (chl), dissolved organic carbon (doc), and suspended minerals (sm), the three primary Color Producing Agents (CPAs). The algorithms utilize a specific hydro-optical (HO) model for each lake. The HO models provide absorption functions for all three CPA components as well as backscatter relationships for the chl, and sm and were generated using in situ inherent/apparent optical (IOP/AOP) data collected with coincident water chemistry (concentration) measurements. These new algorithms provide more accurate chl values than those obtained using the standard OC3 NASA MODIS retrieval when compared to in situ cruise observations, as well as providing the additional information on doc and sm. The suite of atmospheric correction algorithms for MODIS, was also evaluated. In general, the standard NASA algorithm does an adequate correction all of the time
LIU, P.C., and U.F. Pinho. Extreme waves and Rayleigh distribution in the south Atlantic Ocean near the northeast coast of Brazil. The Open Oceanography Journal 6:1-4 (DOI:10.2174/1874252101206010001) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120014.pdf
In this brief communication we present the first result on what have we learned from a long, virtually continuously recorded wave height data set. The data was recorded by Petrobras on a mobile platform located on the northeast Brazilian coast. We found the well-known Rayleigh relation, Hmax/Hs = [ln (N)/2]1/2, fits the data real well for Hmax/Hs up to about 2.2, but diverges distinctly when Hmax/Hs values grow larger. An empirical relation for larger Hmax/Hs can be empirically represented by Hmax/Hs = [ln(N2)/2]1/4.
LIU, P.C., C.H. Wu, A. Bechle, H.S. Chen, and K.R. MacHutchon. What we do not know about freaque waves in the ocean and lakes and where to go from here. Proceedings, 31st International Conference on Oceans, Offshore and Arctic Engineering (OMAE2012), Rio de Janeiro, Brazil, July 1-6, 2012, 7 pp. (2012).
In this paper we point out the lesser known or underexplored aspects of freaque waves. The modern study of freaque waves has been an active research field over the last two decades or so. There have been significant advancements especially in connection with the study of nonlinear physics. We have explored what we DO know, in this paper, we would like to explore what we DO NOT know.
Long, Z., W. Perrie, C.L. Tang, E. Dunlap, and J. WANG. Simulated interannual variations of freshwater content and sea surface height in the Beaufort Sea. Journal of Climate 25(4):1079-1095 (DOI:10.1175/2011JCLI4121.1) (2012). https://journals.ametsoc.org/doi/pdf/10.1175/2011JCLI4121.1
The authors investigate the interannual variations of freshwater content (FWC) and sea surface height (SSH) in the Beaufort Sea, particularly their increases during 2004–09, using a coupled ice–ocean model (CIOM), adapted for the Arctic Ocean to simulate the interannual variations. The CIOM simulation exhibits a (relative) salinity minimum in the Beaufort Sea and a warm Atlantic water layer in the Arctic Ocean, which is similar to the Polar Hydrographic Climatology (PHC), and captures the observed FWC maximum in the central Beaufort Sea, and the observed variation and rapid decline of total ice concentration, over the last 30 years. The model simulations of SSH and FWC suggest a significant increase in the central Beaufort Sea during 2004–09. The simulated SSH increase is about 8 cm, while the FWC increase is about 2.5 m, with most of these increases occurring in the center of the Beaufort gyre. The authors show that these increases are due to an increased surface wind stress curl during 2004–09, which increased the FWC in the Beaufort Sea by about 0.63 m yr21 through Ekman pumping. Moreover, the increased surface wind is related to the interannual variation of the Arctic polar vortex at 500 hPa. During 2004–09, the polar vortex had significant weakness, which enhanced the Beaufort Sea high by affecting the frequency of synoptic weather systems in the region. In addition to the impacts of the polar vortex, enhanced melting of sea ice also contributes to the FWC increase by about 0.3 m yr-1 during 2004–09.
LUO, L., J. WANG, D.J. SCHWAB, H.A. VANDERPLOEG, G.A. LESHKEVICH, X. BAI, H. HU, and D. Wang. Simulating the 1998 spring bloom in Lake Michigan using a coupled physical-biological model. Journal of Geophysical Research 117(C10011):14 pp. (DOI:10.1029/2012JC008216) (2012).
 A coupled physical-biological model is used to simulate the ecosystem characteristics in Lake Michigan. The physical model is the unstructured grid, Finite-Volume Coastal Ocean Model (FVCOM). The biological model is a NPZD model, including phosphorus as the nutrient, which is the limiting element in Lake Michigan, phytoplankton, zooplankton and detritus. The models are driven by observed hourly meteorological forcing in 1998 and the model results are calibrated by satellite and in situ data. The main physical and ecological phenomena in the spring of 1998 are captured. During March to May, a circle-like phytoplankton bloom appears in southern Lake Michigan, which looks like a ‘doughnut’. The formation mechanisms of the prolonged spring bloom are investigated. It is confirmed that the phytoplankton bloom is forced by rapidly increasing temperature and light intensity in spring. The thermal front that develops in spring inhibits the transport of nutrients and phytoplankton from the nearshore to the deeper water. The wind-driven gyre circulation in southern Lake Michigan induces significant offshore transport, which contributes to the establishment of the circular bloom.
Madenjian, C.P., S.R. David, and S.A. POTHOVEN. Effects of activity and energy budget balancing algorithm on laboratory performance of fish bioenergetics mode. Transactions of the American Fisheries Society 141:1328-1337 (DOI:10.1080/00028487.2012.692346) (2012). https://dx.doi.org/10.1080/00028487.2012.692346
We evaluated the performance of the Wisconsin bioenergetics model for lake trout Salvelinus namaycush that were fed ad libitum in laboratory tanks under regimes of low activity and high activity. In addition, we compared model performance under two different model algorithms: (1) balancing the lake trout energy budget on day t based on lake trout energy density on day t and (2) balancing the lake trout energy budget on day t based on lake trout energy density on day t + 1. Results indicated that the model significantly underestimated consumption for both inactive and active lake trout when algorithm 1 was used and that the degree of underestimation was similar for the two activity levels. In contrast, model performance substantially improved when using algorithm 2, as no detectable bias was found in model predictions of consumption for inactive fish and only a slight degree of overestimation was detected for active fish. The energy budget was accurately balanced by using algorithm 2 but not by using algorithm 1. Based on the results of this study, we recommend the use of algorithm 2 to estimate food consumption by fish in the field. Our study results highlight the importance of accurately accounting for changes in fish energy density when balancing the energy budget; furthermore, these results have implications for the science of evaluating fish bioenergetics model performance and for more accurate estimation of food consumption by fish in the field when fish energy density undergoes relatively rapid changes.
Maity, S., A. Jannasch, J. Adamec, T.F. NALEPA, T.O. Hook, and M.S. Sepulveda. Starvation causes disturbance in amino acide and fatty acid metabolism in Diporeia. Comparative Biochemistry and Physiology, Part B 161:348-355 (DOI:10.1016/j.cbpb.2011.12.011) (2012).
The benthic amphipod Diporeia spp. was once the predominant macroinvertebrate in deep, offshore regions of the Laurentian Great Lakes. However, since the early 1990s, Diporeia populations have steadily declined across the area. It has been hypothesized that this decline is due to starvation from increasing competition for food with invasive dreissenid mussels. In order to gain a better understanding of the changes in Diporeia physiology during starvation, we applied two-dimensional gas chromatography coupled with time of flight mass spectrometry (GCXGC/TOF-MS) for investigating the responses in Diporeia metabolome during starvation. We starved Diporeia for 60 days and collected five organisms every 12 days for metabolome analyses. Upon arrival to the laboratory, organisms were flash frozen and served as control (day 0). We observed an increase in lipid oxidation and protein catabolism with subsequent declines of essential amino acids (proline, glutamine, and phenylalanine), down-regulation of glycerophospholipid and sphingolipid metabolism, and decreased polyunsaturated fatty acid abundance in nutritionally stressed Diporeia. Abundance of 1-Iodo-2-methylundecane, a metabolite closely related to insect pheromones, also declined with starvation. This research has further substantiated the applicability of GCXGC/TOF-MS as a research tool in the field of environmental metabolomics. The next step is to apply this new knowledge for evaluating nutritional status of feral Diporeia to elucidate the underlying cause(s) responsible for their decline in the Great Lakes.
Millie, D.F., G.R. Weckman, W.A. Young, J.E. Ivey, H.J. Carrick, and G.L. FAHNENSTIEL. Modeling microalgal abundance with artificial neural networks: Demonstration of a heuristic 'grey box' to deconvolve and quantify environmental influences. Environmental Modelling and Software 38:27-39 (DOI:10.1016/j.envsoft.2012.04.009) (2012).
An artificial neural network (ANN)-based technology e a ‘Grey-Box’, originating the iterative selection, depiction, and quantitation of environmental relationships for modeling microalgal abundance, as chlorophyll (CHL) a, was developed and evaluated. Due to their robust capability for reproducing the complexities underlying chaotic, non-linear systems, ANNs have become popular for the modeling of ecosystem structure and function. However, ANNs exhibit a holistic deficiency in declarative knowledge structure (i.e. a ‘black-box’). The architecture of the Grey-Box provided the benefit of the ANN modeling structure, while deconvolving the interaction of prediction potentials among environmental variables upon CHL a. The influences of (pairs of) predictors upon the variance and magnitude of CHL a were depicted via pedagogical knowledge extraction (multi-dimensional response surfaces). This afforded derivation of mathematical equations for iterative predictive outcomes of CHL a and together with an algorithmic expression across iterations, corrected for the lack of declarative knowledge within conventional ANNs. Importantly, the Grey-Box ‘bridged the gap’ between ‘white-box’ parametric models and black-box ANNs in terms of performance and mathematical transparency. Grey-Box formulations are relevant to ecological niche modeling, identification of biotic response(s) to stress/disturbance thresholds, and qualitative/quantitative derivation of biota-environmental relationships for incorporation within stand-alone mechanistic models projecting ecological structure.
MUZZI, R.W., S.A. CONSTANT, and J.C. LANE. System power controller: A low power circuit board for the control and monitoring of subsystem power in data collection systems. NOAA Technical Memorandum GLERL-154. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 17 pp. (2012). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-154/tm-154.pdf
Power efficiency is important in remote data collection systems that are typically solar-powered. Systems such as the Real-time Coastal Observation Network (ReCON) require controlling power to sensors and components with currents of up to 2 amps and voltages up to 48 volts. Though there are some off-the-shelf solutions available, these systems either consume unnecessary power, or are limited in the amount of current and voltage that they can handle. The design of the System Power Controller board provides eight channels of semiconductor-switched power that can handle the current and voltage requirements while consuming a low amount of quiescent power. Each power channel provides high-side switching of up to 60 volts and currents of up to 2 amps. A low-power microprocessor using an RS-232 serial interface allows programming of the channels, including time delayed events. Three analog input channels allow measuring system voltages, such as solar panel, battery, and system bus voltages. The controller includes a watchdog timer with relay output which allows a full power reboot of the data collection system. The system can be operated with any voltage from 7 to 60 volts, and the entire controller only consumes 0.14 watts of power when powered at 12 volts. The controller board conforms to the PC/104 standard form factor so that it can be mounted on the top of a standard PC/104 stack. The system has proven reliable in several years of field use and has been incorporated as an integral component of the ReCON data collection network.
POTHOVEN, S.A., D.B. Bunnell, C.P. Madenjian, O.T. Gorman, and E.F. Roseman. Energy density of bloaters in the upper Great Lakes. Transactions of the American Fisheries Society 141:772-780 (DOI:10.1080/00028487.2012.675911) (2012). https://www.glerl.noaa/gov/pubs/fulltext/2012/20120020.pdf
We evaluated the energy density of bloaters Coregonus hoyi as a function of fish size across Lakes Michigan, Huron, and Superior in 2008–2009 and assessed how differences in energy density are related to factors such as biomass density of bloaters and availability of prey. Additional objectives were to compare energy density between sexes and to compare energy densities of bloaters in Lake Michigan between two time periods (1998–2001 and 2008–2009). For the cross-lake comparisons in 2008, energy density increased with fish total length (TL) only in Lake Michigan. Mean energy density adjusted for fish size was 8% higher in bloaters from Lake Superior than in bloaters from Lake Huron. Relative to fish in these two lakes, small (<125 mm TL) bloaters from Lake Michigan had lower energy density, whereas large (>175 mm TL) bloaters had higher energy density. In 2009, energy density increased with bloater size, and mean energy density adjusted for fish size was about 9% higher in Lake Michigan than in Lake Huron (Lake Superior was not sampled during 2009). Energy density of bloaters in Lake Huron was generally the lowest among lakes, reflecting the relatively low densities of opossum shrimp Mysis diluviana and the relatively high biomass of bloaters reported for that lake. Other factors, such as energy content of prey, growing season, or ontogenetic differences in energy use strategies, may also influence cross-lake variation in energy density. Mean energy density adjusted for length was 7% higher for female bloaters than for male bloaters in Lakes Michigan and Huron. In Lake Superior, energy density did not differ between males and females. Finally, energy density of bloaters in Lake Michigan was similar between the periods 2008–2009 and 1998–2001, possibly due to a low population abundance of bloaters, which could offset food availability changes linked to the loss of prey such as the amphipods Diporeia spp.
POTHOVEN, S.A., D.L. FANSLOW, and G.L. FAHNENSTIEL. Lipid content of Mysis diluviana in the offshore region of southeastern Lake Michigan in 2009-2010. Journal of Great Lakes Research 38:561-568 (DOI:10.1016/j.jglr.2012.05.003) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120026.pdf
The lipid content of Mysis diluviana in the offshore region of southeastern Lake Michigan was determined in 2009 and 2010. Total lipids (mg) increased with Mysis length, but percent lipids (% dry weight) did not. Increases in lipids for juveniles (b10 mm) were related to increases in structural lipids (i.e., phospholipids and sterols), whereas increases in total lipids for adults were related to increases in storage lipids (i.e., triacylglycerols). Percent lipids varied seasonally, and were in general, highest in spring or late fall for juveniles and small adults (b15 mm). For the largest adults (16+ mm), % lipid content did not vary much over the year in 2009, but in 2010, % lipids peaked in July. The rate of lipid retention differed among cohorts of juveniles, but it did not differ among cohorts of adults. In 2009 and 2010 respectively, 14% and 40% of Mysis >13 mm had lipid content >14%, a value associated with a high percentage of docosahexaenoic acid that may reflect starvation for this size of Mysis. Food availability (chl a levels or zooplankton biomass) was not correlated with Mysis lipid content for any size group of Mysis. Seasonal gradients in food availability might not be large enough to elicit strong responses in lipid content of Mysis.
Rao, Y.R., and D.J. SCHWAB. Laurentian Great Lakes, interaction of coastal and offshore waters. In Encyclopedia of Lakes and Reservoirs. L. Bengtsson, R.W. Herschy, and R.W. Fairbridge (eds.). Springer, Encyclopedia of Earth Sciences Series, 479-484 pp. (DOI:10.1007/978-1-4020-4410-6_264) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120031.pdf
The Laurentian Great Lakes represent an extensive, interconnected aquatic system dominated by its coastal nature. While the lakes are large enough to be significantly influenced by the earth's rotation, they are at the same time closed basins to be strongly influenced by coastal processes (Csanady, 1984). Nowhere is an understanding of how physical, geological, chemical, and biological processes interact in a coastal system more important to a body of water than the Great Lakes. Several factors combine to create complex hydrodynamics in coastal systems, and the associated physical transport and dispersal processes of the resulting coastal flow field are equally complex. Physical transport processes are often the dominant factor in mediating geochemical and biological processes in the coastal environment. Thus, it is critically important to have a thorough understanding of the coastal physical processes responsible for the distribution of chemical and biological species in this zone. However, the coastal regions are not isolated but are coupled with mid-lake waters by exchanges involving transport of materials, momentum, and energy. This review will focus on several mechanisms that contribute to the alongshore and cross-shore transport of material. These are (1) wave-driven processes, (2) coastal boundary layer processes including upwelling and downwelling flows, (3) episodic events such as storms, (4) the thermal bar, and (5) river plumes.
Roberts, J.J., P. Grecay, S.A. Ludsin, S.A. POTHOVEN, H.A. VANDERPLOEG, and T.O. Hook. Evidence of hypoxic foraging forays by yellow perch (Perca flavescens) and potential consequences for prey consumption. Freshwater Biology 57:922-937 (DOI:10.1111/j.1365-2427.2012.02753.x) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120017.pdf1. Previous studies in a variety of ecosystems have shown that ecologically and economically important benthic and bentho-pelagic fishes avoid hypoxic (<2 mg O2 L-1) habitats by moving vertically or horizontally to more oxygenated areas. While avoidance of hypoxic conditions generally leads to a complete shift away from preferred benthic prey, some individual fish continue to consume benthic prey items in spite of bottom hypoxia, suggesting complex habitat utilisation and foraging patterns. For example, Lake Erie yellow perch (Perca flavescens) continue to consume benthic prey, despite being displaced vertically and horizontally by hypolimnetic hypoxia. 2. We hypothesised that hypolimnetic hypoxia can negatively affect yellow perch by altering their distribution and inducing energetically expensive foraging behaviour. To test this hypothesis, we used drifting hydroacoustics and trawl sampling to quantify water column distribution, sub-daily vertical movement and foraging behaviour of yellow perch within hypoxic and normoxic habitats of Lake Erie’s central basin during August-September 2007. We also investigated the effects of rapid changes in ambient oxygen conditions on yellow perch consumption potential by exposing yellow perch to various static and fluctuating oxygen conditions in a controlled laboratory experiment. 3. Our results indicate that, while yellow perch in general avoid hypoxic conditions, some individuals undertake foraging forays into hypoxic habitats where they experience greater fluctuations in abiotic conditions (pressure, temperature and oxygen concentration) than at normoxic sites. However, laboratory results suggest short-term exposure to low oxygen conditions did not negatively impact consumption potential of yellow perch. 4. Detailed understanding of sub-daily individual behaviours may be crucial for determining interactive individual- and ecosystem-level effects of stressors such as hypoxia.
Ryan, D.J., M.S. Sepulveda, T.F. NALEPA, and T.O. Hook. Spatial variation in RNA:DNA ratios of Diporeia spp. in the Great Lakes region. Journal of Great Lakes Research 38(1):9 pp. (DOI:10.1016/j.jglr.2012.01.007) (2012).
Over the past two decades, Diporeia in all of the Laurentian Great Lakes, except Superior, have declined dramatically. These declines have seemingly coincided with expansion of invasive Dreissena polymorpha and D. bugensis, however the exact mechanisms underlying decreasing Diporeia densities are obscure. We explored the use of RNA:DNA (R/D) ratios as a conditional index for Diporeia by experimentally demonstrating that Diporeia R/D responds to periods of starvation. Moreover, during 2008–2009 we collected Diporeia from throughout the Great Lakes and Cayuga Lake (New York, USA), and used R/D ratios to index condition of these in situ collected animals. We evaluated spatial and temporal variation of nucleic acid indices using classification and regression tree (CART) analysis with a suite of environmental variables included as potential predictors. Diporeia R/D of in situ collected specimens exhibited pronounced spatial and temporal variation, but multiple CART models described only a small amount of this variation. While we observed some variation in Diporeia R/D among lakes, nucleic acid ratios appeared to respond weakly to Diporeia population characteristics and local environmental conditions. Specifically, CART analyses revealed that Diporeia R/D was particularly low at extreme depths, and interestingly, Diporeia nucleic acids were not strongly associated with the presence of dreissenids. In summary, while a limited amount of variation in Diporeia R/D was attributable to environmental conditions, the majority of Diporeia R/D variation was unaccounted for. Hence, the causative factors underlying spatio-temporal variation of Diporeia R/D and the mechanistic reasons for Diporeia declines in the Great Lakes remain largely unknown.
Troy, C.D., S. Ahmed, N. HAWLEY, and A. Goodwell. Cross-shelf thermal variability in southern Lake Michigan during the stratified periods. Journal of Geophysical Research 117(C02028):16 pp. (DOI:10.1029/2011JC007148) (2012).
Results from a field experiment in southern Lake Michigan are used to quantify the cross-shelf nearshore variability in Great Lakes temperatures during the stratified season. The experiment was conducted along the Indiana coast of southern Lake Michigan, with temperature and velocity moorings arranged in a cross-shelf transect that extended to approximately 20 km from shore (40 m depth). The field site is noteworthy because of its location at the end of a major axis of an elliptical Great Lake, the relatively mild bathymetric slope, and local shoreline orientation that is perpendicular relative to the dominant summer winds. Measurements demonstrate that the location of the thermocline-bottom intersection is highly variable, causing a wide zone of extreme thermal variability in the nearshore region with time scales of variability ranging from hours to months. Near-inertial internal Poincaré waves are shown to cause large thermocline excursions but primarily only during periods of elevated activity. Several full upwelling events were observed, but in general, they were brief, lasting only 1–2 days, and had very limited spatial extent (2.5 km or less). Nonetheless, the offshore extent of the upwelling front was shown to be reasonably estimated with a simple estimate of the cross-shelf transport caused by alongshore wind events. A persistent feature that determined the zone of elevated thermal variability (the thermocline-shelf intersection point) was the strongly tilted thermocline, which resulted in the thermocline being located very close to shore. No evidence was found to support the hypothesis that internal Kelvin waves affect thermal variability at the study location.
VANDERPLOEG, H.A., S.A. POTHOVEN, G.L. FAHNENSTIEL, J.F. CAVALETTO, J.R. LIEBIG, C.A. STOW, T.F. NALEPA, C.P. Madenjian, and D.B. Bunnell. Seasonal zooplankton dynamics in Lake Michigan: Disentangling impacts of resource limitation, ecosystem engineering, and predation during a critical transition. Journal of Great Lakes Research 38(3):17 pp. (DOI:10.1016/j.jglr.2012.02.005) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120013.pdf
We examined seasonal dynamics of zooplankton at an offshore station in Lake Michigan from 1994 to 2003 and 2007 to 2008. This period saw variable weather, declines in planktivorous fish abundance, the introduction and expansion of dreissenid mussels, and a slow decline in total phosphorus concentrations. After the major expansion of mussels into deep water (2007–2008), chlorophyll in spring declined sharply, Secchi depth increased markedly in all seasons, and planktivorous fish biomass declined to record-low levels. Overlaying these dramatic ecosystem-level changes, the zooplankton community exhibited complex seasonal dynamics between 1994–2003 and 2007–2008. Phenology of the zooplankton maximum was affected by onset of thermal stratification, but there was no other discernable effect due to temperature. Interannual variability in zooplankton biomass during 1994 and 2003 was strongly driven by planktivorous fish abundance, particularly age-0 and age-1 alewives. In 2007–2008, there were large decreases in Diacyclops thomasi and Daphnia mendotae possibly caused by food limitation as well as increased predation and indirect negative effects from increases in Bythotrephes longimanus abundance and in foraging efficiency associated with increased light penetration. The Bythotrephes increase was likely driven in part by decreased predation from yearling and older alewife. While there was a major decrease in epilimnetic–metalimnetic herbivorous cladocerans in 2007–2008, there was an increase in large omnivorous and predacious calanoid copepods, especially those in the hypolimnion. Thus, changes to the zooplankton community are the result of cascading, synergistic interactions, including a shift from vertebrate to invertebrate planktivory and mussel ecosystem impacts on light climate and chlorophyll.
WANG, H.-Y., D.W. Einhouse, D.G. Fielder, L.G. Rudstam, C.S. Vandergoot, A.J. VanDeValk, T.G. Zorn, and T.O. Hook. Maternal and stock effects on egg-size variation among walleye Sander vitreus stocks from the Great Lakes region. Journal of Great Lakes Research 38:477-489 (DOI:10.1016/j.jglr.2012.06.002) (2012).
Fish egg sizes vary intra-specifically among stocks and individuals, and such variation may reflect a combination of maternal and environmental influences. As egg size variation has important implications for individual and population recruitment success, it is useful to quantify egg-size variation and identify potential factors underlying such variation. We evaluated 1) within-stock maternal influences on egg size and 2) the relative elucidatory power of maternal effects versus stock in explaining inter-individual mean egg size based on eggs collected during 2007–2008 from five walleye Sander vitreus stocks in the North American Laurentian Great Lakes region. We used both linear regression models and classification and regression trees (CART) to describe egg-size variation. Egg size tended to increase with female length and for some stocks was greatest for intermediate maternal ages. However, maternal influences on egg size were relatively low and variable between years. In contrast, stock had a stronger effect; walleye egg-size variation was greater among stocks than within stocks. After controlling for the influence of maternal age and length, we found that egg size was relatively small for fish spawning in Maumee and Sandusky Rivers (western Lake Erie), intermediate in Oneida Lake and Tittabawassee River (Saginaw Bay, Lake Huron), and relatively large in Van Buren Bay (eastern Lake Erie) and Little Bay de Noc (northern Green Bay, Lake Michigan). Such inter-stock differences in maternal influence adjusted egg size appeared to be negatively associated with a system's productivity; suggesting a potential adaptive response of egg size to early life habitat conditions.
WANG, J., R.A. ASSEL, S. WALTERSCHEID, A.H. CLITES, and X. BAI. Great Lakes ice climatology update: Winter 2006-2011. Description of the digital ice cover dataset. NOAA Technical Memorandum GLERL-155. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 37 pp. (2012). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-155/tm-155.pdf
A 6-winter digital ice cover data set consisting of 389 ice charts of total ice concentration (the fraction of a unit of surface area covered by ice), was downloaded from the National Ice Center (NIC) website, https://www.natice.noaa.gov/products/great_lakes.html. This report updates GLERL’s 33-winter ice climatology dataset for total ice concentration (Assel 2003, Assel 2005). Data processing and quality control procedures, file structure, format, and naming conventions are described. The data are available as fixed formatted ASCII grids (2.55 km for winter 2006 and 1.275 km for winters 2007-2011) and has been converted to ArcMap feature classes for GIS users. Temporal distribution of the ice charts is summarized in tables. A planned companion report will contain an analysis of these data including spatial patterns of dates of first ice, last ice, ice duration, and ice concentration anomalies [relative to a 30-winter (1973-2002) base period] for each lake by winter season. It will also contain lake averages of total ice cover concentration that portray the seasonal progression of ice cover each winter. Since the last updated ice atlas (Assel 2005), there has been significant change in ice cover on the Great Lakes. This update of the ice atlas should be useful to the research community as well as others who rely on Great Lakes ice data for planning purposes. The technical memorandum that updated the ice atlas for winters 2003, 2004, and 2005 (Assel 2005) did not include ArcGIS feature classes, so those are included here.
WANG, J., X. BAI, H. HU, A.H. CLITES, M.C. COLTON, and B.M. LOFGREN. Temporal and spatial variability of Great Lakes ice cover, 1973-2010. Journal of Climate 25(4):1318-1329 (DOI:10.1175/2011JCLI4066.1) (2012). https://journals.ametsoc.org/doi/pdf/10.1175/2011JCLI4066.1
In this study, temporal and spatial variability of ice cover in the Great Lakes are investigated using historical satellite measurements from 1973 to 2010. The seasonal cycle of ice cover was constructed for all the lakes, including Lake St. Clair. A unique feature found in the seasonal cycle is that the standard deviations (i.e., variability) of ice cover are larger than the climatological means for each lake. This indicates that Great Lakes ice cover experiences large variability in response to predominant natural climate forcing and has poor predictability. Spectral analysis shows that lake ice has both quasi-decadal and interannual periodicities of ~8 and ~4 yr. There was a significant downward trend in ice coverage from 1973 to the present for all of the lakes, with Lake Ontario having the largest, and Lakes Erie and St. Clair having the smallest. The translated total loss in lake ice over the entire 38-yr record varies from 37% in Lake St. Clair (least) to 88% in Lake Ontario (most). The total loss for overall Great Lakes ice coverage is 71%, while Lake Superior places second with a 79% loss. An empirical orthogonal function analysis indicates that a major response of ice cover to atmospheric forcing is in phase in all six lakes, accounting for 80.8% of the total variance. The second mode shows an out-of-phase spatial variability between the upper and lower lakes, accounting for 10.7% of the total variance. The regression of the first EOF-mode time series to sea level pressure, surface air temperature, and surface wind shows that lake ice mainly responds to the combined Arctic Oscillation and El Nino-Southern Oscillation patterns.
WANG, J., X. BAI, D. Wang, D. Wang, H. HU, and X.Y. Yang. Impacts of the Siberian High and Arctic Oscillation on the East Asia winter monsoon: Driving downwelling in the western Bering Sea. Aquatic Ecosystem Health and Management 15(1):20-30 (DOI:10.1080/14634988.2012.648860) (2012).
The relationships between the wind fields of the East Asia winter monsoon (EAWM), the Siberian High (SH), and the Arctic Oscillation (AO) were investigated using reanalysis products. The winter anomalies of the wind fields were systematically examined from the Bering Sea, the Sea of Okhotsk (SoO), the Sea of Japan (SOJ), the East China Sea (ECS), and all the way to the South China Sea (SCS). The sea-level pressure (SLP) difference between the SH and the Aleutian Low (AL) determines the intensity of the EAWM. Wind field anomalies are controlled directly by the SH and indirectly by the AO that has significant impacts on the SH and AL. It is found that +SH enhances the EAWM, while +AO reduces the intensity of the EAWM by reducing the SLP difference (gradient) between the SH and AL; vice versa for the –SH and –AO, respectively. The surface air temperature (SAT) anomalies caused by the +SH result in a significant cooling in the downstream regions and a warming in the upstream regions; vice versa for the negative phase of the SH. The +AO produces a large warming in northern Eurasian and a cooling in the Bering Sea. Furthermore, using a Coupled Ice-Ocean Model (CIOM), it is found that the EAWM can produce a downwelling and dense water formation along the Siberian coast in the western Bering Sea, and also a significant surface-to-bottom convection over the Bering shelf, forming the winter shelf water, which can survive the summer as the so-called cold pool. The cold pool in the Bering Sea has significant impacts on marine ecosystems and habitat including fisheries, which has much implication to other marginal seas of East Asia.
Zorn, T.G., P.W. Seelbach, and E.S. RUTHERFORD. A regional-scale habitat suitability model to assess the effects of flow reduction on fish assemblages in Michigan streams. Journal of the American Water Resources Association 25 pp. (DOI:10.1111 ⁄ j.1752-1688.2012.00656.x) (2012).
In response to concerns over increased use and potential diversion of Michigan’s freshwater resources, and the resulting state legislative mandate, an advisory council created an integrated assessment model to determine the potential for water withdrawals to cause an adverse resource impact to fish assemblages in Michigan’s streams. As part of this effort, we developed a model to predict how fish assemblages characteristic of different stream types would change in response to decreased stream base flows. We describe model development and use in this case study. The model uses habitat suitability information (i.e., catchment size, base-flow yield, and July mean water temperature) for over 40 fish species to predict assemblage structure in an individual river segment under a range of base-flow reductions. By synthesizing model runs for individual fish species at representative segments for each of Michigan’s 11 ecological stream types, we developed curves describing how typical fish assemblages in each type respond to flow reduction. Each stream type-specific, fish response curve was used to identify streamflow reduction levels resulting in adverse resource impacts to characteristic fish populations, the regulatory standard. Used together with a statewide map of stream types, our model provided a spatially comprehensive framework for evaluating impacts of flow withdrawals on biotic communities across a diverse regional landscape.
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