GLERL Publication Abstracts: FY 2012

Capitalized names represent GLERL authors.

 


ADAMACK, A.T., C.A. STOW, D.M. MASON, L.P. Rozas, and T.J. Minello. Predicting the effects of freshwater diversions on juvenile brown shrimp production: A Bayesian-based approach. Marine Ecology Progress Series 444:155-173 (DOI:10.3354/meps09431) (2012). https://www.glerl.noaa.gov/pubs/fulltext/2012/20120001.pdf

Freshwater diversions from the Mississippi River may help restore coastal wetlands in Louisiana, but their implementation will alter temperature and salinity regimes, potentially affecting juvenile shrimp growth and production. We developed a bioenergetics model for brown shrimp Farfantepenaeus aztecus to investigate water temperature and salinity effects on brown shrimp growth. The model used a Bayesian framework that provided estimates of parameter and model uncertainty. Temperature affected shrimp metabolism, whereas salinity modified food availability. Mortality was modeled using a size-dependent function. We examined the effects of diversion timing (February, March, April and May), length (2× 14, as well as 30 and 60 d), temperature change (+1, 0, −1, −5 and –10°C), initial salinity (5, 15, 25), salinity during the diversion (2, 5, 10, 15, 20 and 25) and prey biomass response time (7, 14 and 28 d) on juvenile brown shrimp production. Diversions during February and March had little effect on shrimp, but 30 and 60 d diversions starting in April and May often had large, negative effects on production. April and May diversions that dropped water temperature by 5°C or more could decrease juvenile brown shrimp production by 40 to 60% compared with the baseline, no diversion scenarios. Whether changes in salinity had a positive or negative effect on brown shrimp production depended on the initial salinity of the scenario. Longer diversions and slower prey response times extended the duration brown shrimp were exposed to either the positive or negative effects of diversions, and this magnified the overall (positive or negative) effect on shrimp production. Limiting diversions to February and March when brown shrimp populations are not abundant would minimize negative effects on shrimp production, though managers will be constrained by the needs of other species such as oysters, as well as ecosystem considerations.

Alves, J.H., A. Chawla, H.L. Tolman, D.J. SCHWAB, G.A. LANG, and G. Mann. The Great Lakes wave model at NOAANCEP: challenges and future developments. 12th International Workshop on Wave Hindcasting and Forecasting, Kohala Coast, Hawaii, October 30, 2011 - November 4, 2011. Environment Canada, the Canadian Federal Program of Energy R&D, and the WMO/IOC Joint Technical Commission for Oceanography and Marine Meteorology (JCOMM), 6 pp. (2011). https://www.glerl.noaa.gov/pubs/fulltext/2011/20110041.pdf

In spite of a notion that the nature of wind waves in the Great Lakes is generally benign, intense storms and rapidly changing weather patterns generate severe sea states that develop into serious hazards to marine activities involving commercial and recreational vessels. The Great Lakes basin aggregates more than 1/10th and ¼ of the populations of United States and Canada, respectively. Several states with large contributions to the American economy, such as Wisconsin and Minnesota, make up the lakes margin. Commercial shipping constitutes one of the most costeffective means of transporting raw materials and goods to and from these states, as well as provides an important source of jobs for the region’s population. Providing accurate forecasts of wind waves associated with severe sea states is a critical service towards ensuring the safety of maritime operations in the Great Lakes, with critical consequences to the American economy and public safety.

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.R. 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.M. Keeler, E.A. 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.

Choi, J., C.D. Troy, T.C. Hsieh, N. HAWLEY, and M.J. McCORMICK. A year of internal Poincaré 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.

DYBLE, J., D.C. GOSSIAUX, P.F. LANDRUM, D.R. Kashian, and S.A. POTHOVEN. A kinetic study of accumulation and elimination of microcystin in yellow perch (Perca flavescens) tissue and implications for human fish consumption. Marine Drugs 9:2553-2571 (DOI:10.3390/md9122553) (2011). https://www.glerl.noaa.gov/pubs/fulltext/2011/20110035.pdf

Fish consumption is a potential route of human exposure to the hepatotoxic microcystins, especially in lakes and reservoirs that routinely experience significant toxic Microcystis blooms. Understanding the rates of uptake and elimination for microcystins as well as the transfer efficiency into tissues of consumers are important for determining the potential for microcystins to be transferred up the food web and for predicting potential human health impacts. The main objective of this work was to conduct laboratory experiments to investigate the kinetics of toxin accumulation in fish tissue. An oral route of exposure was employed in this study, in which juvenile yellow perch (Perca flavescens) were given a single oral dose of 5 or 20 μg of microcystin-LR (MC-LR) via food and accumulation in the muscle, liver, and tank water were measured over 24 h. Peak concentrations of the water soluble fraction of microcystin were generally observed 8–10 h after dosing in the liver and after 12–16 h in the muscle, with a rapid decline in both tissues by 24 h. Up to 99% of the total recoverable (i.e., unbound) microcystin was measured in the tank water by 16 h after exposure. The relatively rapid uptake and elimination of the unbound fraction of microcystin in the liver and muscle of juvenile yellow perch within 24 h of exposure indicates that fish consumption may not be a major route of human exposure to microcystin, particularly in the Great Lakes.

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.

Glynn, P., L. Jacobsen, G. Phelps, G. Bawden, V. Grauch, F. Orndort, R. Winston, M. Fienen, M. Cross, and J.F. BRATTON. 3D/4D modelling, visualization and information frameworks: Current U.S. Geological Survey practice and needs. In Three-Dimensional Geological Mapping; Workshop Extended Abstracts. H.A.J. Russell, R.C. Berg, and L.H. Thorleifson (eds.). Geological Survey of Canada Open File 6998, 33-38 pp. (DOI:10.4095/289609) (2011). https://www.glerl.noaa.gov/pubs/fulltext/2011/20110040.pdf

Progress is being made in the ability to visualize and model geologic data and information in 3 spatial dimensions (3D) and sometimes adding time for 4 dimensions (4D). These abilities are enriching the conceptual models and process simulations constructed by geologists and hydrogeologists. Computer technology is also enhancing the visualization and modeling of landscapes and the hydrodynamic simulations of surface waters. Progress needs to be made in visualizing and coupling geologic, hydrologic, atmospheric, and biologic processes together into 3D/4D information frameworks that encompass and integrate observations and simulations across a diversity of spatial and temporal scales and data types. Achieving progress in these areas will also enhance the relevance and effective communication of USGS science to policy makers and to the lay public.

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 zooplankton 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 sensitivity of D. mendotae to hypoxia (≤ mg O2 l-1), supporting the field observations 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 growth 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:10.5670/oceanog.2012.64) (2012). https://dx.doi/org/10.5670/oceanog.2012.64

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., 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.

HU, H., J. WANG, and D. Wang. A model-data study of the 1999 St. Lawrence Island polynya in the Bering Sea. Journal of Geophysical Research 116(C12018):17 (DOI:10.1029/2011JC007309) (2011).

A Coupled Ice Ocean Model (CIOM) and in situ measurements were used to investigate sea ice and the St. Lawrence Island polynya (SLIP) in the Bering Sea in 1999. The modeled 1999 seasonal cycle of ice cover compared well with satellite measurements. The simulated maximum sea ice coverage was ∼0.8 × 106 km2, and the simulated maximum sea ice volume was ∼344 km3. The polynya south of St. Lawrence Island was captured by the CIOM and investigated in depth against the measurements. It was found that an offshore wind was necessary, but not sufficient on its own, for the development of the SLIP. It was found that a strong offshore wind, offshore surface water velocity, and the angle (<60°) between wind and water current are the three major factors for the development of the SLIP. Multiple-variable, linear regression models were developed to confirm these three mechanisms. Yearly potential sea ice production in the SLIP area was estimated to be about 95.7 km3, which accounts for 2.8% of the total potential production of 3393 km3 in the whole Bering Sea. Sea ice contributes to approximately 63% of winter salinity changes in the Bering Shelf (<200 m), while the SLIP can contribute more than twice the local salinity changes. The relationships among wind, sea ice, and surface ocean current were examined. The classic Ekman drift theory (that surface water velocity drifts 45° to the right of the wind direction) is modified to be 50.4° on the ice-covered Bering Shelf due to the year-round existence of a background northward ocean transport.

Ivan, L.N., E.S. RUTHERFORD, and T.H. JOHENGEN. Impacts of adfluvial fish on the ecology of two Great Lakes tributaries. Transactions of the American Fisheries Society 140:1670-1682 (DOI:10.1080/00028487.2011.642233) (2011).

Anadromous and adfluvial fish can transport high concentrations of nutrients and energy into streams during spawning runs. While the ecological effects of their spawning migrations are variable, in some instances these fish contribute to increased nutrient concentrations, primary productivity, invertebrate biomass, and resident fish growth and survival in the nutrient-poor streams of the Pacific Northwest. In tributaries of the Great Lakes, the effects of introduced salmonid and native adfluvial fish are poorly documented. We conducted field experiments to determine the effects of a semelparous fall fish, Chinook salmon Oncorhynchus tshawytscha, and an iteroparous spring fish, steelhead O. mykiss, on the ecology and productivity of two tributaries to the Muskegon River, Michigan, a Lake Michigan tributary. We sampled stream biota and water chemistry before and after the introduction of Chinook salmon carcasses and eggs in the fall and steelhead eggs in the spring in a tributary stream with natural spawning runs and in another tributary stream without runs but with carcass and egg additions. There was no response in terms of invertebrate density or water chemistry to spawning migrations or salmon carcass introductions in either tributary. The density of resident brown trout Salmo trutta increased in both stream types after the introduction of salmon carcasses in the fall, and energy consumption increased after the addition of salmon eggs in the fall and spring in the manipulated stream. Based on stomach content analysis, fish that had eggs in their stomachs also consumed more energy than fish that did not consume eggs. The results suggest that adfluvial fish may affect some tributaries of the Great Lakes by providing high-energy food sources to resident stream fish, but the potential effect of this egg consumption on resident fish growth and survival requires more research

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 245:199-207 (DOI:10.1016/j.ecolmodel.2012.03.030) (2012). https://dx.doi.org/10.1016/j.ecolmodel.2012.03.030

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.

Liu, Y., G.B. Arhonditsis, C.A. STOW, and D. Scavia. Predicting the hypoxic-volume in Chesapeake Bay with the Streeter-Phelps model: A Bayesian approach. Journal of the American Water Resources Association 47(6):1348-1363 (DOI:10.1111/j.1752-1688.2011.00588.x) (2011).

Hypoxia is a long-standing threat to the integrity of the Chesapeake Bay ecosystem. In this study, we introduce a Bayesian framework that aims to guide the parameter estimation of a Streeter–Phelps model when only hypoxic volume data are available. We present a modeling exercise that addresses a hypothetical scenario under which the only data available are hypoxic volume estimates. To address the identification problem of the model, we formulated informative priors based on available literature information and previous knowledge from the system. Our analysis shows that the use of hypoxic volume data results in reasonable predictive uncertainty, although the variances of the marginal posterior parameter distributions are usually greater than those obtained from fitting the model to dissolved oxygen (DO) profiles. Numerical experiments of joint parameter estimation were also used to facilitate the selection of more parsimonious models that effectively balance between complexity and performance. Parameters with relatively stable posterior means over time and narrow uncertainty bounds were considered as temporally constant, while those with time varying posterior patterns were used to accommodate the interannual variability by assigning year-specific values. Finally, our study offers prescriptive guidelines on how this model can be used to address the hypoxia forecasting in the Chesapeake Bay area.

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. ASME, 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?

LOFGREN, B.M., T.S. HUNTER, and J. Wilbarger. Effects of using air temperature as a proxy for potential evapotranspiration in climate change scenarios of Great Lakes basin hydrology. Journal of Great Lakes Research 37:744-752 (DOI:10.1016/j.jglr.2011.09.006) (2011).

Hydrologic impacts of climate change are regularly assessed with hydrologic models that use air temperature as a proxy to compute potential evapotranspiration (PET). This approach is taken in the Large Basin Runoff Model (LBRM), which has been used several times for calculation of the runoff from the terrestrial part of the Great Lakes basin under climate change scenarios, with the results widely cited. However, a balance between incoming and outgoing energy, including the latent heat of evaporation, is a fundamental requirement for a land surface, and is not enforced under this approach. For calculating PET and evapotranspiration (ET) in climate change scenarios, we use an energy budget-based approach to adjusting the PET as an alternative that better satisfies conservation of energy. Using this new method, the increase in ET under enhanced greenhouse gas concentrations has reduced magnitude compared to that projected using the air temperature proxy. This results in either a smaller decrease in net basin supply and smaller drop in lake levels than using the temperature proxy, or a reversal to increased net basin supply and higher lake levels. An additional reason not to rely on a temperature proxy relation is that observational evidence demonstrates that the correlation between air temperature and ET (or PET) is restricted to the mean annual cycle of these variables. This brings into question the validity of air temperature as a proxy for PET when considering non-annual variability and secular changes in the climate regime.

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.

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.

Madenjian, C.P., E.S. RUTHERFORD, M. Blouin, B.J. Sederberg, and J.R. Elliott. Spawning habitat unsuitability: An impediment to Cisco rehabilitation in Lake Michigan? Journal of North American Fisheries Management 31:905-913 (DOI:10.1080/02755947.2011.632065) (2011). https://www.tandfonline.com/doi/abs/10.1080/02755947.2011.632065

The cisco Coregonus artedi was one of the most important native prey fishes in Lake Michigan and in the other four Laurentian Great Lakes. Most of the cisco spawning in Lake Michigan was believed to have occurred in Green Bay. The cisco population in Lake Michigan collapsed during the 1950s, and the collapse was attributed in part to habitat degradation within Green Bay. Winter water quality surveys of lower Green Bay during the 1950s and 1960s indicated that the bottom dissolved oxygen (DO) concentration was less than 2 mg/L throughout much of the lower bay, and most cisco eggs would not successfully hatch at such low DO concentrations. To determine present-day spawning habitat suitability in lower Green Bay, we compared cisco egg survival in lower Green Bay with survival at a reference site (St. Marys River, Michigan–Ontario) during 2009. We also conducted winter water quality surveys in lower Green Bay and the St. Marys River during 2009 and 2010. Cisco egg survival in lower Green Bay averaged 65.3%, which was remarkably similar to and not significantly different from the mean at the St. Marys River site (64.0%). Moreover, the lowest bottom DO concentrations recorded during the winter surveys were 11.2 mg/L in lower Green Bay and 12.7 mg/L in the St. Marys River. These relatively high DO concentrations would not be expected to have any negative effect on cisco egg survival. We conclude that winter water quality conditions in lower Green Bay were suitable for successful hatching of cisco eggs and that water quality during the egg incubation period did not represent an impediment to cisco rehabilitation in Lake Michigan. Our approach to determining spawning habitat suitability for coregonids would be applicable to other aquatic systems.

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.

Manley, T.O., M.J. McCORMICK, J.C. Gascard, P. Tillier, K.L. Hunkins, and P.L. Manley. An initial view of subsurface Lagrangian observations in Lake Champlain: General patterns, cross-lake flow and coastal currents. Journal of Great Lakes Research:76-87 (DOI:10.1016/j.jglr.2011.07.006) (2012).

Subsurface free-drifting floats operating in the Main Lake of Lake Champlain in 2002 and 2004 showed the presence of 1) small circular to elliptical motion away from coastal boundaries, 2) linear to curvilinear motion associated with alongshore currents and 3) subsurface westward cross-lake flow located within the base of the epilimnion and upper metalimnion (10–16 m) followed by large displacements up to 48 km by a coastal current. This subsurface westward flow is believed to be driven by linked upwelling and downwelling regimes on either side of the lake. Subsurface moorings deployed for ~34 days in 2007 and within1 km of Whallon Bay's (NY) western shore showed that Kelvin wave dynamics and a high-speed subsurface jet located above the metalimnic core and > 600 m offshore could account for these large southerly transports. This subsurface jet may be linked to the cross-lake flow due to similar vertical positioning. The southern concave shape of Whallon Bay also appears to be the cause of high-speed northward-flowing currents within 400 m of the shore.

MIEHLS, A.L.J., S.D. Peacor, and A.G. McAdam. Genetic and maternal effects on tail spine and body length in the invasive spiny water flea (Bythotrephes longimanus). Evolutionary Applications:11 pp. (DOI:10.1111/j.1752-4571.2011.00221.x) (2011). https://onlinelibrary.wiley.com/doi/10.1111/j.1752-4571.2011.00221.x/abstract

Interest in the evolution of invasive species has grown in recent years, yet few studies have investigated sources of variation in invasive species traits experiencing natural selection. The spiny water flea, Bythotrephes longimanus, is an invasive zooplankton in the Great Lakes that exhibits seasonal changes in tail spine and body length consistent with natural selection. Evolution of Bythotrephes traits, however, depends on the presence and magnitude of quantitative genetic variation, which could change within or across years. Clonal analysis of wild-captured Bythotrephes indicated that variance components for distal spine length were variable among but not within years. Spine length was always heritable but was not always influenced by maternal effects. In contrast, variance components for body length varied both within and among years, but likewise body length was always heritable and not always influenced by maternal effects. Results indicate that important Bythotrephes traits have heritable variation comparable to native species and other invasive species that would enable an evolutionary response to natural selection. This evolutionary capacity could contribute to the widespread success and dramatic effects of Bythotrephes invasion in systems with diverse biotic and abiotic conditions.

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 >13mm 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.

POTHOVEN, S.A., H.A. VANDERPLOEG, D.M. Warner, J.S. Schaeffer, S.A. Ludsin, R.M. Claramunt, and T.F. NALEPA. Influences on Bythotrephes longimanus life-history characteristics in the Great Lakes. Journal of Great Lakes Research:134-141 (DOI:10.1016/j.jglr.2011.10.003) (2012).

We compared Bythotrephes population demographics and dynamics to predator (planktivorous fish) and prey (small-bodied crustacean zooplankton) densities at a site sampled through the growing season in Lakes Michigan, Huron, and Erie. Although seasonal average densities of Bythotrephes were similar across lakes (222/m2 Erie, 247/m2 Huron, 162/m2 Michigan), temporal trends in abundance differed among lakes. In central Lake Erie where Bythotrephes' prey assemblage was dominated by small individuals (60%), where planktivorous fish densities were high (14,317/ha), and where a shallow water column limited availability of a deepwater refuge, the Bythotrephes population was characterized by a small mean body size, large broods with small neonates, allocation of length increases mainly to the spine rather than to the body, and a late summer population decline. By contrast, in Lake Michigan where Bythotrephes' prey assemblage was dominated by large individuals (72%) and planktivorous fish densities were lower (5052/ha), the Bythotrephes population was characterized by a large mean body size (i.e., 37–55% higher than in Erie), small broods with large neonates, nearly all growth in body length occurring between instars 1 and 2, and population persistence into fall. Life-history characteristics in Lake Huron tended to be intermediate to those found in Lakes Michigan and Erie, reflecting lower overall prey and predator densities (1224/ha) relative to the other lakes. Because plasticity in life history can affect interactions with other species, our findings point to the need to understand life-history variation among Great Lakes populations to improve our ability to model the dynamics of these ecosystems.

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., S.B. Brandt, D.L. FANSLOW, S.A. Ludsin, S.A. POTHOVEN, D. Scavia, and T.O. Hook. Effects of hypoxia on consumption, growth, and RNA:DNA ratios of young yellow perch. Transactions of the American Fisheries Society 140:1574-1586 (DOI:10.1080/00028487.2011.638576) (2011).

As in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring phenomenon in Lake Erie’s central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to affect the growth rates of yellow perch Perca flavescens, a species of ecological and economic importance in the lake. To this end, we (1) conducted laboratory experiments to quantify the effects of reduced dissolved oxygen on consumption, somatic growth, and RNA:DNA ratios (an index of short-term growth) of young yellow perch and (2) explored the effects of bottom hypoxia on young yellow perch growth in Lake Erie’s central basin by collecting individuals in hypoxic and normoxic regions of the lake and quantifying their RNA:DNA ratios. Yellow perch consumption and growth in our experiments declined under hypoxic conditions (≤2 mg O2/L). While yellow perch RNA:DNA ratios responded strongly to experimental temperature, nucleic acid ratios were not significantly affected by dissolved oxygen or feeding ration. We did, however, observe a positive correlation between yellow perch growth and RNA:DNA ratios at low temperatures (11oC). The nucleic acid ratios of yellow perch collected in Lake Erie varied spatiotemporally, but their patterns were not consistent with hypoxia. In short, while yellow perch consumption and growth rates respond directly and negatively to low oxygen conditions, these responses are not necessarily reflected in RNA:DNA ratios. Moreover, in central Lake Erie, where yellow perch can behaviorally avoid hypoxic areas, the RNA:DNA ratios of yellow perch do not respond strongly to bottom hypoxia. Thus, this study suggests that there is no strong negative effect of bottom hypoxia on the growth of young yellow perch in Lake Erie.

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.pdf

1. 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(2):187-195 (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(2):336-352 (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 Nin´┐Żo Southern Oscillation patterns.

WANG, J., X. BAI, D. Wang, D. Wang, H. HU, and X. 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.

Wang, T.N., S.A. Bailey, D.F. REID, T.H. JOHENGEN, P.T. Jenkins, C.J. Wiley, and H.J. MacIsaac. Efficacy of NaCl brine for treatment of ballast water against freshwater invasions. Journal of Great Lakes Research:72-77 (DOI:10.1016/j.lglr.2011.10.001) (2012).

Currently, all transoceanic vessels entering the Great Lakes must perform ballast water exchange or saltwater flushing, procedures designed to reduce the risk of new biological invasions from ballast water. Vessels not in compliance with these regulations presently have limited, often costly, and/or time-consuming alternatives available. Treatment with sodium chloride brine at an initial concentration of 230‰ has been proposed as an emergency ballast water management option and is examined here. Six shipboard trials were conducted under operational conditions to determine the efficacy of brine ballast water treatment. Trials were conducted on three vessels with full ballast tanks and on three vessels with only residual ballast water. Brine distribution in tanks was adequate, noting that vessel movement was essential to ensure mixing into ballast water or ballast residuals. Once mixing has occurred, approximately 25 hour exposure to 45‰ brine or 1 hour exposure to 115‰ brine is required to effectively exterminate freshwater zooplankton. Brine appears to be a cost-effective and relatively safe procedure that could be implemented immediately for emergency treatment of non-compliant ballast water to reduce risk of new invasions in the Great Lakes.

Wynne, T.T., R.P. Stumpf, M.C. Tomlinson, D.J. SCHWAB, G.Y. Watabayashi, and J.D. Christensen. Estimating cyanobacterial bloom transport by coupling remotely sensed imagery and a hydrodynamic model. Ecological Applications 21(7):2709-2721 (DOI:10.1890/10-1454.1) (2011).

The ability to forecast the transport of harmful cyanobacterial blooms in the Laurentian Great Lakes is beneficial to natural resource managers concerned with public health. This manuscript describes a method that improves the prediction of cyanobacterial bloom transport with the use of a preoperational hydrodynamic model and high temporal resolution satellite imagery. Two scenarios were examined from separate cyanobacterial blooms in western Lake Erie, USA. The first scenario modeled bloom position and extent over the span of 13 days. A geographic center, or centroid, was calculated and assigned to the bloom from observed satellite imagery. The bloom centroid was projected forward in time, and the projected position was compared to the final observed bloom centroid. Image pixels flagged as cyanobacterial bloom were compared between the initial image and the final image, and this was assumed as persistence. The second bloom scenario was modeled for a period of 12 days, and the results were framed in an ecological context in an effort to gain further understanding of cyanobacterial bloom dynamics. These modeling techniques can be incorporated into an operational forecasting system.

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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