GLERL Publication Abstracts: FY 2007

Arhonditsis, G.B., H.W. Paerl, L.M. Valdes-Weaver, C.A. STOW, L.J. Steinberg, and K. H. Reckhow. Application of Bayesian structural equation modeling for examining phytoplankton dynamics in the Neuse River Estuary (North Carolina, USA). Estuarine, Coastal, and Shelf Science 72:63-80 (2007).

We introduce a Bayesian structural equation modeling framework to explore the spatiotemporal phytoplankton community patterns in the Neuse River Estuary (study period 1995-2001). The initial hypothesized model considered the influence of the physical environment (flow, salinity, and light availability), nitrogen (dissolved oxidized inorganic nitrogen, and total dissolved inorganic nitrogen), and temperature on total phytoplankton biomass and phytoplankton community structure. Generally, the model gave plausible results and enabled the identification of the longitudinal role of the abiotic factors on the observed phytoplankton dynamics. River flow fluctuations and the resulting salinity and light availability changes (physical environment) dominate the up-estuary processes and loosen the coupling between nitrogen and phytoplankton. Further insights into the phytoplankton community response were provided by the positive path coefficients between the physical environment and diatoms, chlorophytes, and cryptophytes in the down-estuary sections. The latter finding supports an earlier hypothesis that these three groups dominate the phytoplankton community during high freshwater conditions as a result of their faster nutrient uptake and growth rates and their tolerance on low salinity conditions. The relationship between dissolved inorganic nitrogen concentrations and phytoplankton community becomes more apparent as we move to the down-estuary sections. A categorization of the phytoplankton community into cyanobacteria, dinoflagellates and an assemblage that consists of diatoms, chlorophytes, and cryptophytes provided the best results in the upper and middle segments of the estuary. Finally, the optimal down-estuary grouping aggregates diatoms and chlorophytes, lumps together dinoflagellates with cryptophytes, while cyanobacteria are treated separately. These structural shifts in the temporal phytoplankton community patterns probably result from combined bottom-up and top-down control effects.

BELETSKY, D., D.J. SCHWAB, and M.J. McCORMICK. Modeling the 1998-2003 summer circulation and thermal structure in Lake Michigan. Journal of Geophysical Research 111:C10010, doi:10.1029/2005JC003222 (2006).

A three-dimensional primitive equation numerical model was applied to Lake Michigan on a 2 km grid for 6 consecutive years to study interannual variability of summer circulation and thermal structure in 1998–2003. The model results were compared to long-term observations of currents and temperature at seven moorings and two NOAA buoys. The accuracy of modeled currents improved considerably relative to previous summer circulation modeling done on a 5 km grid, while the accuracy of temperature simulations remained the same. Particle trajectory model results were also compared with satellite-tracked surface drifter observations. Large-scale circulation patterns tend to be more cyclonic (counterclockwise) toward the end of summer as the thermocline deepens and density effects become more important. Circulation in southern Lake Michigan appears to be more variable than circulation in northern Lake Michigan. An important new feature not previously seen in observations was found in southern Lake Michigan: an anticyclonic gyre extending northward from the southern shore of Lake Michigan, sometimes occupying the entire southern basin.

BRANDT, S.B., and M.B. LANSING. The International Field Years on Lake Erie (IFYLE). In State of the Great Lakes Annual Report, 20th Anniversary. Office of the Great Lakes, Michigan Department of Environmental Quality, Lansing, MI, 26-28 (2006).

The National Oceanic and Atmospheric Administration’s (NOAA’s) Great Lakes Environmental Research Laboratory (GLERL), in collaboration with researchers from the U.S., Canada, and Europe, have initiated what is believed to be the largest, most comprehensive, multidisciplinary research effort ever conducted on Lake Erie: the International Field Years on Lake Erie (IFYLE). Lake Erie faces wide and varied threats to its health and integrity, including harmful algal blooms (HABs) in the west basin, recurring low oxygen episodes (“dead zones”) in the central basin, and invasive species as well as extremes in natural phenomena such as high and low water levels, and climate variability. Each of these threats has the potential to disrupt normal food webs and ecosystem processes, and thus, jeopardize Lake Erie’s ability to provide healthy fish populations, safe drinking water, and bacteria-free beaches. Since all of these factors are interrelated, the scientific framework for effective management will require ecosystem-level research, particularly relative to biological-physical-chemical interactions on a lake-wide basis and over a range of time and space scales. Full report available at:

Cangelosi, A.A., N.L. Mays, M.D. Balcer, E.D. Reavie, D.M. Reid, R. STURTEVANT, and X. Gao. The response of zooplankton and phytoplankton from the North American Great Lakes to filtration. Harmful Algae 6:547-566 (2007).

Filtration of ballast water was investigated as a means of minimizing the introduction of nonindigenous zooplankton and phytoplankton by ships visiting the North American Great Lakes-St. Lawrence Seaway system (GLSLSS). An automatic backwash screen filtration (ABSF) system with nominal filtration options of 25, 50, or 100 um was mounted on the deck of an operating Seaway-sized dry bulk carrier, the MV Algonorth. Water was pumped through the ABSF with a deck mounted pump at 341 m3 hr-1 during routine ship operations in the GLSLSS, and effectiveness of the various screen pore sizes at removing taxonomic categories of zooplankton and phytoplankton was measured using matched treatment and control ballast tanks. The smallest pore sizes (25 and 50 um) performed better than the 100 um pore size at removing biological material. There was no difference in the filtration efficiency of the 25 and 50 um screens relative to macro- or microzooplankton in these tests, but this result was probably due to low densities of macrozooplankton, and soft-bodied (aloricate) characteristics of the microzooplankton present. The 25 and 50 um pore sizes were subjected to more controlled tests on board a stationary barge platform equipped with triplicate 700 L catchment bins moored in Duluth Harbor of Lake Superior. In these tests, filter pore size, organism size and rigidity influenced zooplankton removal efficiency by the ABSF. The 25 um screen reduced both macrozooplankton and microzooplankton significantly more than the 50 um screen. Zooplankton width was more determinative of filtration performance than length, and both filters removed loricate species of rotifers significantly more efficiently than aloricate species of the same length and width size classes. The 25 and 50 um ABSF also significantly reduced algal densities, with the exception of colonial and filamentous green algae (50 um only). Filter efficiency relative to algal particles was influenced by filter pore size, organism morphology and structure, and intake density, while algal particle size was not determinative. This research provides compelling evidence that 25 or 50 um filtration is a potentially powerful means of reducing densities of organisms discharged by ships operating in the Great Lakes but an additional treatment step would be necessary to effectively minimize risk and meet the International Maritime Organization’s discharge standards associated with organisms of all sizes in the water column.

Chu, P., J.G.W. Kelley, A.-J. Zhang, G.A. LANG, and K.W. Bedford. Skill assessment of NOS Lake Erie Operational Forecast System (LEOFS). NOAA Technical Memorandum NOS CS 12. NOAA Office of Coast Survey, Coast Survey Development Lab, Silver Spring, MD, 73 pp. (2007).

This document describes the Lake Erie Operational Forecast System (LEOFS) and an assessment of its skill. The lake forecast system, based on a hydrodynamic model, uses near real-time atmospheric observations and numerical weather prediction forecast guidance to produce three-dimensional forecast guidance of water temperature and currents and two-dimensional forecasts of water levels. LEOFS is the result of technology transfer of the Great Lake Forecasting System (GLFS) and the Great Lakes Coastal Forecasting System (GLCFS) from The Ohio State University (OSU) and NOAA’s Great Lakes Environmental Research Laboratory (GLERL) to NOAA’s National Ocean Service.

CROLEY, T.E. II., J.F. Atkinson, and D.F. RAIKOW. Hydrologic - Hydraulic - Ecologic resource sheds. Proceedings of the Second IASTED International Conference, Water Resources Management, Honolulu, HI, August 20-22, 2007. 164-169 pp. (2007).

We can quantify source areas contributing material to a location during various time periods as resource sheds. Various kinds of resource sheds and their source material distributions are defined. For watershed hydrology, we compute resource sheds and their source material distributions with a spatially distributed hydrology model by tracing material departing from a cell (say 1 km2) over one time interval and arriving at the watershed mouth in another time interval. This requires modeling all cells, but only tracing contributions from one at a time. By then combining these simulations for all cell loadings, we construct a map of the contributions over the entire watershed for specific departure and arrival time intervals. We then combine results of several sets of simulations to determine the source distribution for any time period and infer resource sheds from these mappings. For lake circulation, we discuss the construction of resource sheds and their source distributions in the lake, by using lake circulation models to drive particle tracers in reverse time, and subsequent correction. We present Maumee watershed examples, discuss methods of computation reduction and linkage with lake circulation models, construct joint resource sheds in Lake Erie, and suggest areas of extension.

CROLEY, T. E. II., C. He, J.F. Atkinson, and D.F. RAIKOW. Resource shed definitions and computations. NOAA Technical Memorandum GLERL-141. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 35 pp. (2007).

When we consider a location with a material (e.g., water, pollutant, sediment) passing through it, we can ask: Where did the material come from and how long did it take to reach the location? We can quantify the answer by defining the areas contributing to this location during various time periods as resource sheds. Various kinds of resource sheds and their source material distributions are rigorously defined and properties derived. For watershed hydrology, we compute resource sheds and their source material distributions with a spatially distributed hydrology model by tracing material departing from a cell (say 1 km2) over one time interval and arriving at the watershed mouth in another time interval. This requires modeling all cells, but only tracing contributions from one at a time. By then combining these simulations for all cell loadings, we construct a map of the contributions over the entire watershed for specific departure and arrival time intervals. We then combine results of several sets of simulations to determine the source distribution for any time period and infer resource sheds from these mappings. For lake circulation, we discuss the construction of resource sheds and their source distributions in the lake, by using lake circulation models to drive particle tracers in reverse time, and subsequent correction. We present examples for the Maumee River watershed in northern Ohio, discuss methods of computation reduction, discuss linkage with a lake circulation model to construct joint resource sheds in Lake Erie, and suggest areas of extension for the future.

CROLEY, T.E. II., and C.F.M. Lewis. Warmer and drier climates that make terminal Great Lakes. Journal of Great Lakes Research 32:852-869 (2006).

A recent empirical model of glacial-isostatic uplift showed that the Huron and Michigan lake level fell tens of meters below the lowest possible outlet about 7,900 14C years BP when the upper Great Lakes became dependent for water supply on precipitation alone, as at present. The upper Great Lakes thus appear to have been impacted by severe dry climate that may have also affected the lower Great Lakes. While continuing paleoclimate studies are corroborating and quantifying this impacting climate and other evidence of terminal lakes, the Great Lakes Environmental Research Laboratory applied their Advanced Hydrologic Prediction System, modified to use dynamic lake areas, to explore the deviations from present temperatures and precipitation that would force the Great Lakes to become terminal (closed), i.e., for water levels to fall below outlet sills. We modeled the present lakes with pre-development natural outlet and water flow conditions, but considered the upper and lower Great Lakes separately with no river connection, as in the early Holocene basin configuration. By using systematic shifts in precipitation, temperature, and humidity relative to the present base climate, we identified candidate climates that result in terminal lakes. The lakes would close in the order: Erie, Superior, Michigan-Huron, and Ontario for increasingly drier and warmer climates. For a temperature rise of T�C and a precipitation drop of P% relative to the present base climate, conditions for complete lake closure range from 4.7T + P > 51 for Erie to 3.5T + P > 71 for Ontario.

DeMARCHI, C., A. Georgakakos, and C. Peters-Lidard. Probabilistic estimation of precipitation combining geostationary and TRMM satellite data. Proceedings of Symposium HS3007 at IUGG2007, Remote Sensing for Environmental Monitoring and Change Detection, Perugia, Italy, July 2007. IAHS Publication 316, International Association of Hydrological Sciences, pp. 70-77 (2007).

This paper presents a methodology for estimating precipitation that combines precipitation rates observed by the TRMM satellite with infrared/-visible (IR/VIS) images by geostationary satellites. The method detects IR patterns associated with convective storms and characterizes their evolution phases. Precipitation rates are estimated for each phase using IR/VIS and terrain information. The approach is shown to improve the integration of TRMM precipitation rates and IR/VIS data by differentiating major storms from smaller events and noise, and by separating the precipitation regime characteristic of each storm phase. Further, the procedure explicitly quantifies the uncertainty of the precipitation estimates by computing their probability distribution. The methodology was tested in the Lake Victoria basin during the period 1996–1998 against data from >100 rain gauges, showing lower bias and better correlation with ground data than commonly used methods, and reproducing the variability of precipitation over a range of temporal and spatial scales.

DeMARCHI, C., A. Georgakakos, and C. Peters-Lidard. Uncertainty characterization in a combined IR/Microwave scheme for remote sensing of precipitation. Proceedings, Symposium HS2004 at IUGG2007, Quantification and Reduction of Predictive Uncertainty for Sustainable Water Resources Management, Perugia, Italy, July 2007. International Association of Hydrological Sciences , IAHS Publication 313, pp. 70-77 (2007).

This paper presents a methodology for estimating precipitation that combines data from the precipitation radar aboard the TRMM satellite with infrared/visible (IR/VIS) images by geostationary satellites. The approach estimates half-hour precipitation based on IR/VIS data, storm stage, and terrain, and quantifies the uncertainty of the precipitation estimates by computing their full probability distribution. The probabilistic characterization is composed of a binomial distribution for the probability of rain and a lognormal distribution for the conditional rain intensity. Temporal and spatial autocorrelations are fully accounted for by using spatially optimal estimator methods (kriging). The procedure is tested in the Lake Victoria basin over the period 1996–1998 against data from more than one hundred rain gauges, showing lower bias and better correlation with ground data than commonly used methods and reproducing precipitation variability over a range of temporal and spatial scales.

Fong, T.T., L.S. Mansfield, D.L. Wilson, D.J. SCHWAB, S.L. Molloy, and J.B. Rose. Massive microbiological groundwater contamination associated with a waterborne outbreak in Lake Erie, South Bass Island, Ohio. Environmental Health Perspectives 115(6):856-864 (2007).

A groundwater-associated outbreak affected approximately 1,450 residents and visitors of South Bass Island, Ohio, between July and September 2004. OBJECTIVES: To examine the microbiological quality of groundwater wells located on South Bass Island, we sampled 16 wells that provide potable water to public water systems 15–21 September 2004. METHODS: We tested groundwater wells for fecal indicators, enteric viruses and bacteria, and protozoa (Cryptosporidium and Giardia). The hydrodynamics of Lake Erie were examined to explore the possible surface water–groundwater interactions. RESULTS: All wells were positive for both total coliform and Escherichia coli. Seven wells tested positive for enterococci and Arcobacter (an emerging bacterial pathogen), and F+-specific coliphage was present in four wells. Three wells were positive for all three bacterial indicators, coliphages, and Arcobacter; adenovirus DNA was recovered from two of these wells. We found a cluster of the most contaminated wells at the southeast side of the island. CONCLUSIONS: Massive groundwater contamination on the island was likely caused by transport of microbiological contaminants from wastewater treatment facilities and septic tanks to the lake and the subsurface, after extreme precipitation events in May–July 2004. This likely raised the water table, saturated the subsurface, and along with very strong Lake Erie currents on 24 July, forced a surge in water levels and rapid surface water–groundwater interchange throughout the island. Landsat images showed massive influx of organic material and turbidity surrounding the island before the peak of the outbreak. These combinations of factors and information can be used to examine vulnerabilities in other coastal systems. Both wastewater and drinking water issues are now being addressed by the Ohio Environmental Protection Agency and the Ohio Department of Health.

Ge, J., J. Qi, B M. LOFGREN, N. Moore, N. Torbick, and J.M. Olson. Impacts of land use/cover classification accuracy on regional climate simulations. Journal of Geophysical Research 112(D05107, doi:10.1029/2006JD007404):12 (2007).

Land use/cover change has been recognized as a key component in global change. Various land cover data sets, including historically reconstructed, recently observed, and future projected, have been used in numerous climate modeling studies at regional to global scales. However, little attention has been paid to the effect of land cover classification accuracy on climate simulations, though accuracy assessment has become a routine procedure in land cover production community. In this study, we analyzed the behavior of simulated precipitation in the Regional Atmospheric Modeling System (RAMS) over a range of simulated classification accuracies over a 3 month period. This study found that land cover accuracy under 80% had a strong effect on precipitation especially when the land surface had a greater control of the atmosphere. This effect became stronger as the accuracy decreased. As shown in three follow-on experiments, the effect was further influenced by model parameterizations such as convection schemes and interior nudging, which can mitigate the strength of surface boundary forcings. In reality, land cover accuracy rarely obtains the commonly recommended 85% target. Its effect on climate simulations should therefore be considered, especially when historically reconstructed and future projected land covers are employed.

Ge, Z., and P.C. LIU. A time-localized response of wave growth process under turbulent winds. Annales Geophysicae 25:1253-1262 (2007).

Very short time series (with lengths of approximately 40 s or 5-7 wave periods) of wind velocity fluctuations and wave elevation were recorded simultaneously and investigated using the wavelet bispectral analysis. Rapid changes in the wave and wind spectra were detected, which were found to be intimately related to significant energy transfers through transient quadratic wind-wave and wave wave-induced interactions. A possible pattern of energy exchange between the wind and wave fields was further deduced. In particular, the generation and variation of the strong wave-induced perturbation velocity in the wind can be explained by the strengthening and diminishing of the associated quadratic interactions, which cannot be unveiled by linear theories. On small time scales, the wave-wave quadratic interactions were as active and effective in transferring energy as the wind-wave interactions. The results also showed that the wind turbulence was occasionally effective in transferring energy between the wind and the wave fields, so that the background turbulence in the wind cannot be completely neglected. Although these effects are all possibly significant over short times, the time-localized growth of the wave spectrum may not considerably affect the long-term process of wave development.

Godby, N.A., Jr., E.S. Rutherford, and D.M. MASON. Diet, feeding rate, growth, mortality, and production of juvenile steelhead in a Lake Michigan tributary. North American Journal of Fisheries Management 27:578-592 (2007).

Steelhead (Oncorhynchus mykiss) support valuable sport fisheries in the Great Lakes but are largely sustained by stocking. In many Great Lakes tributaries, steelhead spawning and nursery habitats are limited by hydropower dams, and natural recruitment may be supplemented by habitats in adjacent coldwater creeks. In 1998–2001, we investigated the potential for natural production of steelhead in the Muskegon River, Michigan, a tributary to Lake Michigan, through analysis of parr diet categories, consumption, growth, survival, and production in the main-stem Muskegon River and in Bigelow Creek. We used electrofishing surveys to estimate parr growth and survival from changes in fish weight and density over time. We estimated diet from gut content analysis and consumption from bioenergetics model analysis. Average fall density of parr in Bigelow Creek was 20-fold higher than in the Muskegon River. Average summer daily mortality rate of parr in the Muskegon River was nearly threefold higher than in Bigelow Creek. Overwinter mortality rates of parr were low in both habitats. Few yearling and older parr were present in the Muskegon River relative to Bigelow Creek. Age-0 parr primarily consumed benthic invertebrates. Macroinvertebrate prey densities were sufficient to support high parr growth rates in both rivers. Parr grew at similar rates but consumed 84% more per day in the Muskegon River, which had higher water temperatures than Bigelow Creek. Age-0 production was fivefold higher in Bigelow Creek than in the Muskegon River. High mortalities of parr in the Muskegon River were correlated with summer water temperatures exceeding 21oC. Average summer temperatures in Bigelow Creek (17oC) were optimal for parr survival. Our results were consistent with data from other Great Lakes tributaries and suggest that small tributary creek habitats contribute disproportionately to steelhead recruitment from large impounded watersheds by providing optimal thermal refugia for parr during summer.

Great Lakes Beach Association, NOAA Great Lakes Environmental Research Laboratory, Michigan Sea Grant Program, U.S. Environmental Protection Agency, and U.S. Geological Survey. Great Lakes beach health research needs: Workshop summary. NOAA Technical Memorandum GLERL-138. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 27 pp. (2006).

The Great Lakes coastline is the largest in the continental United States, containing hundreds of beaches and providing recreational opportunities for millions of visitors, thus making it a vital part of the Midwest economy. Too often the health of these beaches is compromised by water quality degradation particularly from the introduction of sewage and accompanying pathogens. These events, whether chronic or episodic, not only reduce the quality of recreation but threaten human health. Public officials responsible for protecting natural resources and visitor health seek ways to remediate these problems and to communicate any health threats in a timely manner. Increasingly sophisticated scientific information is required to provide solutions to these problems not only for the Great Lakes but along coastlines worldwide.

He, C., and T. E. CROLEY II. Application of a distributed large basin runoff model in the Great Lakes basin. Control Engineering Practice 15:1001-1011 (2007).

This paper analyzes the application of a spatially distributed large basin runoff model (DLBRM) in the Great Lakes Basin of the United States and Canada and discusses four essential components of operational hydrologic model development: model structure, model input, model calibration, and Geographical Information System (GIS)-model interface. The results indicate that large scale operational hydrologic models that are based on mass continuity equations and include land surface, soil zones, and groundwater components require fewer parameters, are less data demanding, and are particularly suitable for solving water resources problems over large spatial and temporal scales than many other models. Use of GIS-model interfaces is essential for utilizing the existing multiple digital databases in defining model input and in facilitating model implementation and applicability.

Holker, F., H. Dorner, T. Schulze, S. S. Haertel-Borer, S.D. PEACOR, and T. Mehner. Species-specific responses of planktivorous fish to the introduction of a new piscivore: implications for prey fitness. Freshwater Biology 52(doi:10.1111/j.1365-2427.2007.01810.x):1793-1806 (2007).

1. Antipredator behaviour by the facultative planktivorous fish species roach (Rutilus rutilus), perch (Perca fluviatilis) and rudd (Scardinius erythrophthalmus) was studied in a multi-year whole-lake experiment to evaluate species-specific behavioural and numerical responses to the stocking of pikeperch (Sander lucioperca), a predator with different foraging behaviour than the resident predators large perch (P. fluviatilis) and pike (Esox lucius).
2. Behavioural responses to pikeperch varied greatly during the night, ranging from reduced activity (roach and small perch) and a shift in habitat (roach), to no change in the habitat use and activity of rudd. The differing responses of the different planktivorous prey species highlight the potential variation in behavioural response to predation risk from species of similar vulnerability.
3. These differences had profound effects on fitness; the density of species that exhibited an antipredator response declined only slightly (roach) or even increased (small perch), whereas the density of the species that did not exhibit an antipredator response (rudd) decreased dramatically (by more than 80%).
4. The maladaptive behaviour of rudd can be explained by a ‘behavioural syndrome’, i.e. the interdependence of behaviours expressed in different contexts (feeding activity, antipredator) across different situations (different densities of predators).
5. Our study extends previous studies, that have typically been limited to more controlled situations, by illustrating the variability in intensity of phenotypic responses to predators, and the consequences for population density, in a large whole-lake setting.

Holloway, G., F. Dupont, E. Golubeva, S. Hakkinen, E. Hunke, M. Jin, M. Karcher, F. Kauker, M. Maltrud, M. A. Morales-Maqueda, W. Maslowski, G. Platov, D. Stark, M. Steele, T. Suzuki, J. WANG, and J. Zhang. Water properties and circulation in Arctic Ocean models. Journal of Geophysical Research 112(C04503, doi: 10.1029/2006JC003642):18 pp. (2007).

[1] As a part of the Arctic Ocean Model Intercomparison Project, results from 10 Arctic ocean/ice models are intercompared over the period 1970 through 1999. Models’ monthly mean outputs are laterally integrated over two subdomains (Amerasian and Eurasian basins), then examined as functions of depth and time. Differences in such fields as averaged temperature and salinity arise from models’ differences in parameterizations and numerical methods and from different domain sizes, with anomalies that develop at lower latitudes carried into the Arctic. A systematic deficiency is seen as AOMIP models tend to produce thermally stratified upper layers rather than the ‘‘cold halocline’’, suggesting missing physics perhaps related to vertical mixing or to shelf-basin exchanges. Flow fields pose a challenge for intercomparison. We introduce topostrophy, the vertical component of Vx?D where V is monthly mean velocity and ?D is the gradient of total depth, characterizing the tendency to follow topographic slopes. Positive topostrophy expresses a tendency for cyclonic ‘‘rim currents’’. Systematic differences of models’ circulations are found to depend strongly upon assumed roles of unresolved eddies.

HÖÖK, T.O., M.J. McCORMICK, E.S. Rutherford, D.M. MASON, and G.S. Carter. Short-term water mass movements in Lake Michigan: Implications for larval fish transport. Journal of Great Lakes Research 32:728-737 (2006).

Water mass movement within the Great Lakes may rapidly transport fish larvae from favorable nursery areas to less favorable habitats, thereby affecting recruitment success. During 2001 and 2002, we released satellite-tracked drifting buoys in eastern Lake Michigan to follow discrete water masses, and used ichthyoplankton nets to repeatedly sample larval fish within these water masses. Observed nearshore water currents were highly variable in both direction and velocity. Current velocities far exceeded potential larval fish swimming speeds, suggesting that currents can potentially rapidly advect fish larvae throughout the lake. Evidence suggests that while paired drifters released during 2002 were able to track relatively small alewife (Alosa pseudoharengus) and yellow perch (Perca flavescens) larvae within an alongshore coastal current, paired drifters released during 2001 failed to track larger alewife larvae when flow was more offshore and highly variable. These results are consistent with the decorrelation scales associated with alongshore and offshore transport.

HÖÖK, T.O., E.S. Rutherford, D.M. MASON, and G.S. Carter. Hatch dates, growth rates, and over-winter mortality of age-0 alewives in Lake Michigan: Implications for habitat-specific recruitment success. Transactions of the American Fisheries Society 136:1298-1312 (2007).

Alewives, Alosa pseudoharengus, are key components of Laurentian Great Lakes ecosystems and spawn in multiple habitat types. Exploration of alewife early life history dynamics within these different habitats should help identify important recruitment processes. During 2001–2003, we quantified physical (temperature, transparency) and biotic (chlorophyll a, zooplankton densities) habitat factors and collected age-0 alewives (using ichthyoplankton nets and trawls) in a nearshore region of Lake Michigan and Muskegon Lake, Michigan (a drowned river mouth lake connected to Lake Michigan). We characterized alewife hatch dates, individual condition, growth, mortality, and size-dependent overwinter survival to infer differences in habitat-specific recruitment success. Temperature, turbidity, chlorophyll-a concentrations, and densities of zooplankton prey were consistently higher in Muskegon Lake than in nearshore Lake Michigan. On average, young alewives in Muskegon Lake hatched earlier, grew faster, were in better condition (based on a biphasic length–weight relationship), and had greater survival than alewives in Lake Michigan. By the end of the growing season, young alewives in Muskegon Lake obtained a larger size than those residing in nearshore Lake Michigan, suggesting that they were more likely to survive through winter (a period of intense size-selective mortality) and ultimately recruit to the adult population.

Jin, M., C. Deal, J. WANG, V. Alexander, R. Gradinger, S. Saitoh, T. Iida, Z. Wan, and P. Stabeno. Ice-associated phytoplankton blooms in the southeastern Bering Sea. Geophysical Research Letters 34(L06612, doi:10.1029/2006GL028849):6 pp. (2007).

Ice-associated phytoplankton blooms in the southeastern Bering Sea can critically impact the food web structure, from lower tropic level production to marine fisheries. By coupling pelagic and sea ice algal components, our 1-D ecosystem model successfully reproduced the observed ice-associated blooms in 1997 and 1999 at the NOAA/PMEL mooring M2. The model results suggest that the ice-associated blooms were seeded by sea ice algae released from melting sea ice. For an ice-associated bloom to grow and reach the typical magnitude of phytoplankton bloom in the region, ice melting-resulted low-salinity stratification must not be followed by a strong mixing event that would destroy the stratification. The ice-associated blooms had little impacts on the annual primary production, but had significant impacts in terms of shifting phytoplankton species, and the timing and magnitude of the bloom. These changes, superimposed on a gradual ecosystem shift attributed to global warming, can dramatically alter the Bering Sea ecosystem.

KASHIAN, D.R., R. E. Zuellig, K.A. Mitchell, and W H. Clements. The cost of tolerance: Sensitivity of stream benthic communities to UV-B and metals. Ecological Applications 17(2):365-375 (2007).

The ability to tolerate disturbance is a defense strategy that minimizes the effects of damage to fitness and is essential for sustainability of populations, communities, and ecosystems. Despite the apparent benefits of tolerance, there may be an associated cost that results in a deficiency of a system to respond to additional disturbances. Aquatic ecosystems are often exposed to a variety of natural and anthropogenic disturbances, and the effects of these compound perturbations are not well known. In this investigation, we examine whether tolerance to one stressor, metals, results in a cost of increased sensitivity to an additional stressor, ultraviolet-B (UV-B) radiation.
Heavy metal pollution is recognized as a major environmental problem in Rocky Mountain streams. These high-elevation, typically clear streams may be at particular risk to elevated UVB levels associated with reduced levels of ozone. Microcosm experiments were conducted using natural stream benthic communities collected from a reference site and a site with a long-term history of heavy-metal pollution. Direct and interactive effects of heavy metals and UV-B radiation on structural and functional characteristics of benthic communities were evaluated among four treatments: control, UV-B, metals, and metal and UV-B. Communities from the metal-polluted site were more tolerant of metals but less tolerant to UV-B compared to reference communities. Increased mayfly drift and reduced metabolism in response to metal exposure were observed in reference communities but not in the metal-polluted communities. In contrast to these results, UV-B radiation significantly reduced community metabolism, total macroinvertebrate abundance, and abundances of mayflies, caddisflies, and dipterans from the metal-polluted site, but had no effects on benthic communities from the reference site. ANOSIM results demonstrated that community responses differed among treatments at both sites. Metals had the largest impact on community differences at both sites, while UV-B had greater impacts at the metal-polluted site. This research demonstrates the need to account for potential costs associated with tolerance and that these costs can result in behavioral, structural, and functional impacts to benthic communities.

Kelley, J.G.W., P. Chu, A.-J. Zhang, and G.A. LANG. Skill assessment of NOS Lake Superior Operational Forecast System (LSOFS). NOAA Technical Memorandum NOS CS 9. NOSS Office of Coast Survey, Coast Survey Development Lab, Silver Spring, MD, 48 pp. (2007).

This document describes the Lake Superior Operational Forecast System (LSOFS) and an assessment of its skill. The lake forecast system, based on a hydrodynamic model, uses near real-time atmospheric observations and numerical weather prediction forecast guidance to produce three-dimensional forecast guidance of water temperature and currents and two-dimensional forecasts of water levels for Lake Superior. LSOFS is the result of technology transfer of the Great Lake Forecasting System (GLFS) and Great Lakes Coastal Forecasting System (GLCFS) from The Ohio State University (OSU) and NOAA’s Great Lakes Environmental Research Laboratory (GLERL) to NOAA’s National Ocean Service.

Kelley, J G.W., P. Chu, A.-J. Zhang, G.A. LANG, and D.J. SCHWAB. Skill assessment of NOS Lake Michigan Operational Forecast System (LMOFS). NOAA Technical Memorandum NOS CS 8. NOAA, Office of Coast Survey, Coast Survey Development Laboratory, Silver Spring, MD, 67 pp. (2007).

This document describes the Lake Michigan Operational Forecast System (LMOFS) and an assessment of its skill. The lake forecast system, based on a hydrodynamic model, uses near real-time atmospheric observations and numerical weather prediction forecast guidance to produce three-dimensional forecast guidance of water temperature and currents and two-dimensional forecasts of water levels for Lake Michigan. LMOFS is the result of technology transfer of the Great Lake Forecasting System (GLFS) and Great Lakes Coastal Forecasting System (GLCFS) from The Ohio State University (OSU) and NOAA’s Great Lakes Environmental Research Laboratory (GLERL) to NOAA’s National Ocean Service.

Lee, C., D.J. SCHWAB, D. BELETSKY, J. Stroud, and B.M. Lesht. Numerical modeling of mixed sediment resuspension, transport, and deposition during the March 1998 episodic events in southern Lake Michigan. Journal of Geophysical Research 112(C02018, doi:10.1029/2005JC003419):17 pp. (2007).

A two-dimensional sediment transport model capable of simulating sediment resuspension of mixed (cohesive plus noncohesive) sediment is developed and applied to quantitatively simulate the March 1998 resuspension events in southern Lake Michigan. Some characteristics of the model are the capability to incorporate several floc size classes, a physically based settling velocity formula, bed armoring, and sediment availability limitation. Important resuspension parameters were estimated from field and laboratory measurement data. The model reproduced the resuspension plume (observed by the SeaWIFS satellite and field instruments) and recently measured sedimentation rate distribution (using radiotracer techniques) fairly well. Model results were verified with field measurements of suspended sediment concentration and settling flux (by ADCPs and sediment traps). Both wave conditions and sediment bed properties (critical shear stress, fine sediment fraction, and limited sediment availability or source) are the critical factors that determine the concentration distribution and width of the resuspension plume. The modeled sedimentation pattern shows preferential accumulation of sediment on the eastern side of the lake, which agrees with the observed sedimentation pattern despite a predominance of particle sources from the western shoreline. The main physical mechanisms determining the sedimentation pattern are (1) the two counter-rotating circulation gyres producing offshore mass transport along the southeastern coast during northerly wind, and (2) the settling velocity of sediment flocs which controls the deposition location.

LESHKEVICH, G.A., and S.V. Nghiem. Algorithm development for operational satellite SAR classification and mapping of Great Lakes ice cover. Proceedings, OceanSAR 2006 - Third Workshop on Coastal and Marine Applications of SAR, St. John's, Newfoundland, Canada, October 25, 2006. 3 pp. (2006).

During the 1997 winter season, shipborne polarimetric backscatter measurements of Great Lakes (freshwater) ice types using the Jet Propulsion Laboratory (JPL) C-band scatterometer, together with surface-based ice physical characterization measurements and environmental parameters were acquired. This polarimetric data set, measured at incident angles from 0o to 60o for all polarizations, was processed to radar cross-section to establish a library of signatures (look-up table) for different ice types. Using this library of signatures, computer analysis of calibrated ERS-2 and RADARSAT ScanSAR images of Great Lakes ice cover using a supervised classification technique indicates that different ice types in the ice cover can be identified and mapped, and that wind speed and direction can have an influence on the classification of water as ice based on single frequency, single polarization data.

LIU, P.C. A chronology of freaque wave encounters. Geofizika 24(1):57-70 (2007).

Freaque waves is a newly coined term that combines the two common synonymously used terms of rogue and freak waves. Long before the recent sweeping recognition of the existence of freaque waves, stories of encounters with the unexpected and unusually large waves in the ocean have been told and proffered among seafarers throughout the ages. After being ignored or dismissed for decades, freaque waves have now emerged as an apropos oceanographic research subject. The current literature consists of various conjectured mechanisms aimed at explaining some aspects for the occurrence of freak waves. Examples are: the linear or nonlinear superposition of waves that lead to larger instability and wave heights, and the focusing of wave energy through time and space, through areas of variable surface ocean currents, and through nonlinear systems such as various attributes of the nonlinear Schrodinger equation. These diversified theoretical postulations mainly demonstrate that it is possible to simulate some wave profiles that might resemble the appearance of freaque waves. At the present, however, none of these conjectures can be readily substantiated by measurements or shed new light on how a freak wave can be recognized before its encounter. There is not even an available universal definition for freaque waves beyond the simple rule of thumb of a height greater than twice the significant wave height. Contrary to some claims, freaque waves are presently not predictable. The following compilation is an attempt to create a chronology of some of the most-well-known or reliably reported freaque wave encounters, along with their respective, relevant, and easily accessible sources. Each case is generally composed of year, date, location, name of the vessel, a brief description of the encounter, and extent of damages if known. While efforts have been made to incorporate all known cases of freaque waves that were witnessed, alleged, or adverted to, clearly no premise of accuracy or completeness can be vouched for here. Additions, corrections, and modifications are sincerely welcome.

LIU, P.C., C.-H. Tsai, and H.S. Chen. On the growth of ocean waves. Ocean Engineering 34:1472-1480 (2007).

The availability of 10 h of continuous, uninterrupted field measurements of wind waves recorded in the western Pacific and containing a complete wave growth episode, has provided a distinct opportunity for us to make a novel, unprecedented examination of detailed wave growth processes. We found that the significance of the size of data used in the measurement, which can only be addressed with continuous and uninterrupted measurements, reflected the ineptness of the conventional approach toward further detailed understanding of realistic wave growth processes, as the conventional 20 min data size essentially stamped out any dynamics with time scale below 20 min. While our conventional understanding and modeling were generally operative and useful, they left no real vestige on time localized mechanisms such as wave grouping or wave breaking processes all with time scales much less than 20 min.

LOFGREN, B.M. Land surface roughness effects on lake effect precipitation. Journal of Great Lakes Research 32:839-851 (2006).

The land use of the Great Lakes region has changed significantly during historical times, and continues to change. As a preliminary step in investigating the overall effect that this might have on climate, attention is focused here on one forcing factor and one effect—land surface roughness length and lake effect precipitation, respectively—that are anticipated to be particularly sensitive pieces of the land use-climate interaction. On both a monthly basis and in an individual case of lake effect precipitation, a reduction of land surface roughness reduces the total amount of lake effect precipitation. It also reduces the degree to which the precipitation is focused on the area closest to the lakeshore. The largest reductions occur immediately adjacent to the lakeshore in an area smaller than the overall lake effect zone. In the individual lake effect event that is investigated here, precipitation increases in some places farther inland when surface roughness is reduced. Because this increase in precipitation farther inland appears to be associated with significant topography, this result is most valid for lake effect zones where there is a high topographic relief, such as near southeastern Lake Erie (the main focus of this study), and to the south and east of Lake Ontario. This displacement in location of precipitation is particularly crucial where the boundary of the drainage basin is near the shoreline, and can indicate a flux of moisture out of the Great Lakes drainage basin and into another basin.

LUDSIN, S. A., C. H. HAND, J. E. Marsden, B. J. Fryer, and E. A. Howe. Micro-elemental analysis of statoliths as a tool for tracking tributary origins of sea lamprey. 2006 Project Completion Report, Great Lakes Fishery Commission, Ann Arbor, MI, 106 pp. (2006).

The analysis of otolith micro-elemental composition has been a valuable tool for differentiating among local spawning populations, and identifying origins of recruits to the fishery. Herein, we explored whether the analysis of sea lamprey (Petromyzon marinus) statolith micro-elemental composition by laser-ablation inductively-coupled plasma-mass spectrometry (LA-ICP-MS) could be used as a tool to 1) discriminate among sea lamprey larvae collected from Lake Huron tributaries, and 2) classify a mixed-sample of unknown-origin parasites or spawners back to their natal source. By providing the GLFC with an alternate means, to labor-intensive tagging studies, to determine relative contributions of parasites and spawners from various spawning tributaries, we sought to enhance the GLFC’s ability to prioritize sea lamprey control efforts. As part of this effort, we analyzed statoliths of larvae collected in 45 Lake Huron tributaries during 2004 and 2005, as well as 72 female spawners collected in the Thessalon and Opequeoc rivers during 2005. Our analyses were conducted at three different classification scales: by geologic zone (n = 4 zones), by watershed (n = 9 watersheds), and by individual stream (n = 45 streams). Similar to a previous GLFC pilot study conducted using Proton Induced X-ray Emission (PIXE), we found that LA-ICP-MS analysis of statolith micro-elemental composition could be used to reliably differentiate among individuals produced in different regions (i.e., geologic zones, watersheds, streams), with the level of successful discrimination varying with classification scale. Regardless of the scale of classification, rubidium (Rb), strontium (Sr), manganese (Mn), and barium (Ba) were always most important for discrimination, with zinc (Zn), magnesium (Mg), and lead (Pb) being less useful. Analysis of water and sediment samples from 31 Lake Huron and Lake Champlain tributaries helps to understand these differences in utility for discrimination in that concentrations of Rb, Sr, Mn, and Ba in larval statoliths and ambient water were correlated, whereas concentrations of Zn, Mg, and Pb were not. Analysis of left-right statolith pairs also demonstrate that Zn, Mg, and Pb were not analytically stable in our analyses for reasons that are not entirely clear. Ultimately, using Rb, Sr, Mn, and Ba in maximum-likelihood estimation analyses conducted on a mixed-stock of adult spawners collected in 2005, we found that the sources contributing the greatest proportion of adults to our mixed sample were: 1) the Southern Lake Superior geologic zone (located north of Lake Huron); 2) the Wanipiti-French watershed; and 3) Beavertail Creek, Mississagi River, Lauzon Creek, Garden River, and Musquash River. However, these results need to be viewed with some caution, given our lack of success in accurately typing a sample of known-origin (tagged) spawners back to their natal streams in parallel study conducted in Lake Champlain. In discussing these results, we identify analytical and research needs that could further support our findings, and advance the use of statolith microchemistry as a means to identify natal origins of parasitic and adult sea lamprey in Lake Huron.

MacHutchon, K.R., and P.C. LIU. Measurement and analysis of ocean wave fields in four dimensions. Proceedings of the 26th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2007, San Diego, CA, June 10-15, 2007. 5 pp. (2007).

Ocean wave data comprises either instrumentally-measured data or model-derived data, and the former type of data is preferred in the offshore industry. Instrumental data can be considered to be comprised of both directly measured sea surface displacement data and derived data, from the acceleration of buoys. It has been found that significant differences can occur between sea surface displacements, which are recorded in steep waves by fixed probes or lasers (Eulerian), or by free-floating buoys (Lagrangian). This has given rise to the situation where wave buoy data should not be used to estimate wave profiles in steep waves. Short crested and heaped waves, in moderate to high sea states, can also cause a problem when recording wave data at a fixed point, when it comes to determining the representivity of the results across a wave field. Recorded wave data is used as the basis for the development as well as the verification of all wave models and, given the above uncertainties, the authors propose a new wave measurement method, using the recently developed Automated Trinocular Stereo Imaging System (ATSIS), for the recording of three-dimensional surface wave displacements with respect to time. The ATSIS is a novel system, which measures the temporal evolution of three- dimensional wave characteristics for analysis. An oblique configuration for the system effectively increases spatial coverage, allowing observations of wave phenomena over a broad range of temporal and spatial scales. The details in the paper provide a solution of quantifying the behaviour of irregular, non-linear, and directionally spread (short crested waves), and provides an efficient method for developing better design criteria in the future.

MASON, D.M., B. Nagy, M. Butler, S. Larsen, D.J. Murie, and W.J. Lindberg. Integration of technologies for understanding the functional relationship between reef habitat and fish growth and production. In Emerging Technologies for Reef Fisheries Research and Management. J.C. Taylor (Ed.). NOAA Professional Paper NMFS No. 5. NOAA National Marine Fisheries Service, Seattle, WA, 105-116 (2006).

Functional linkage between reef habitat quality and fish growth and production has remained elusive. Most current research is focused on correlative relationships between a general habitat type and presence/absence of a species, an index of species abundance, or species diversity. Such descriptive information largely ignores how reef attributes regulate reef fish abundance (density-dependent habitat selection), trophic interactions, and physiological performance (growth and condition). To determine the functional relationship between habitat quality, fish abundance, trophic interactions, and physiological performance, we are using an experimental reef system in the northeastern Gulf of Mexico where we apply advanced sensor and biochemical technologies. Our study site controls for reef attributes (size, cavity space, and reef mosaics) and focuses on the processes that regulate gag grouper (Mycteroperca mscrolepis) abundance, behavior and performance (growth and condition), and the availability of their pelagic prey. We combine mobile and fixed-active (fisheries) acoustics, passive acoustics, video cameras, and advanced biochemical techniques. Fisheries acoustics quantifies the abundance of pelagic prey fishes associated with the reefs and their behavior. Passive acoustics and video allow direct observation of gag and prey fish behavior and the acoustic environment, and provide a direct visual for the interpretation of fixed fisheries acoustics measurements. New application of biochemical techniques, such as Electron Transport System (ETS) assay, allow the in situ measurement of metabolic expenditure of gag and relates this back to reef attributes, gag behavior, and prey fish availability. Here, we provide an overview of our integrated technological approach for understanding and quantifying the functional relationship between reef habitat quality and one element of production - gag grouper growth on shallow coastal reefs.

Moisander, P.H., H.W. Paerl, J. DYBLE, and K. Sivonen. Phosphorus limitation and diel control of nitrogen-fixing cyanobacteria in the Baltic Sea. Marine Ecology Progress Series 345:41-50 (2007).

Up to half of the annual new nitrogen inputs into the Baltic Sea originate from blooms of N2-fixing cyanobacteria. Estimates of the magnitude of this new nitrogen vary, partially because relatively few studies have investigated short-term changes in N2-fixation rates in response to environmental changes in situ, including phosphorus availability, one of the major factors limiting N2 fixation in the system. We examined cyanobacterial N2 fixation in response to phosphorus amendments over the diel cycle during 2002 and 2003 in the Baltic Sea, when both Nodularia spumigena and Aphanizomenon sp. formed blooms. Phosphorus stimulated N2 fixation in the open-sea areas in the Northern Baltic Proper and Gulf of Finland during both years. In microcosm experiments, both chlorophyll a concentration and N2 fixation were positively related to time (R2 = 0.79 and 0.54, respectively) for at least 4.5 d after the P amendment. N2 fixation was enhanced up to 3-fold within 4.5 d by a single P pulse. N2 fixation continued in the dark at 16 to 61% of maximum rates during the day, and there were no consistent changes in nitrogenase enzyme abundance in response to darkness. Immunoblotting showed that N2 fixation is not regulated in response to darkness by size modifications of the Fe and MoFe proteins in N. spumigena or of the Fe protein of Aphanizomenon sp. Capability to fix N2 at high rates at night allows these cyanobacteria to maximize their utilization of periodic P pulses for subsequent growth.

NALEPA, T.F., D.L. FANSLOW, S.A. POTHOVEN, A.J. FOLEY III, and G.A. LANG. Long-term trends in benthic macroinvertebrate populations in Lake Huron over the past four decades. Journal of Great Lakes Research 33(2):421-436 (2007).

Surveys of the benthic macroinvertebrate community were conducted in the main basin of Lake Huron in 2000 and 2003, and in Georgian Bay and North channel in 2002. Results were compared to surveys conducted in the 1960s and early 1970s. Although data of earlier surveys were inconsistent, our best estimates suggest that total density of the four major benthic taxa (Diporeia spp., Oligochaeta, Sphaeriidae, and Chironomidae) in the main basin declined dramatically between the early 1970s and 2000. Populations of all major taxa continued to decline between 2000 and 2003, particularly Diporeia and Sphaeriidae. Diporeia was rare or absent in the southern end of the lake and in some nearshore areas in 2000, and by 2003 was not found at depths < 50 m except in the far northeastern end of the lake. Densities of the major taxa in Georgian Bay and North Channel in 2002 were not different from densities in 1973 despite differences in survey methods. A limited study in southern Georgian Bay, however, found that densities of both Diporeia and Sphaeriidae declined to zero at most sites between 2000 and 2004. The population of Dreissena polymorpha was stable in all lake areas, but Dreissena bugensis increased, particularly at the 31–50 m depth interval in the main basin. Since there were no extensive surveys in Lake Huron in the period between nutrient abatement (late 1970s) and the establishment of Dreissena (early 1990s), it is difficult to determine relative roles of these events on observed declines. However, since phosphorus loads have been stable since the early 1980s, declines between 2000 and 2003 can likely be attributed to Dreissena.

NALEPA, T.F., D.L. FANSLOW, S.A. POTHOVEN, A.J. FOLEY III, G.A. LANG, S.C. Mozley, and M.W. Winnell. Abundance and distribution of benthic macroinvertebrate populations in Lake Huron in 1972 and 2000-2003. NOAA Technical Memorandum GLERL-140. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 33 pp. (2007).

This technical report gives results of benthic macroinvertebrate surveys conducted in Lake Huron between 2000 and 2003, and in 1972. Objectives of the former surveys were to document the status of benthic communities, and to assess changes over time. Over the past 20-30 years, the benthic community of Lake Huron has been the least studied of all the Great Lakes. While a number of benthic surveys were conducted in Lake Huron in the early 1970s (Schelske and Roth 1972; Shrivastava 1974; Loveridge and Cook 1976; Great Lakes Research Division-University of Michigan, unpublished data), no wide-scale surveys have been conducted in the lake since this time period. With broad changes now occurring in many of the other Great Lakes because of phosphorus abatement and the introduction of invasive species, an assessment of the benthic community in Lake Huron is both timely and needed. Of particular interest is the status of the benthic amphipod Diporeia spp. This ecologically-important organism has declined dramatically in Lakes Erie, Michigan, and Ontario (Dermott and Kerec 1997, Nalepa et al. 1998, Lozano et al 2001, Nalepa et al 2006) since the introduction and spread of Dreissena polymorpha (zebra mussel) and Dreissena bugensis (quagga mussel), and information is needed to determine if similar declines have occurred in Lake Huron.

PANGLE, K.L., S.D. PEACOR, and O.E. Johansson. Large nonlethal effects of an invasive invertebrate predator on zooplankton population growth rate. Ecology 88(2):402-412 (2007).

We conducted a study to determine the contribution of lethal and nonlethal effects to a predator’s net effect on a prey’s population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus, on zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both systems indicated that the prey species Daphnia mendotae, Daphnia retrocurva, and Bosmina longirostris inhabited deeper portions of the water column as Bythotrephes biomass increased, possibly as an avoidance response to predation. This induced migration reduces predation risk but also can reduce birth rate due to exposure to cooler temperatures. We estimated the nonlethal (i.e., resulting from reduced birth rate) and lethal (i.e., consumptive) effects of Bythotrephes on D. mendotae and Bosmina longirostris. These estimates used diel field survey data of the vertical gradient of zooplankton prey density, Bythotrephes density, light intensity, and temperature with growth and predation rate models derived from laboratory studies. Results indicate that nonlethal effects played a substantial role in the net effect of Bythotrephes on several prey population growth rates in the field, with nonlethal effects on the same order of magnitude as or greater (up to 10-fold) than lethal effects. Our results further indicate that invasive species can have strong nonlethal, behaviorally based effects, despite short evolutionary coexistence with prey species.

PEACOR, S.D. Behavioural response of bullfrog tadpoles to chemical cues of predation risk are affected by cue age and water source. Hydrobiologia 573:39-44 (doi 10.1007/s10750-006-0256-3) (2006).

When confronted by signals of predators presence, many aquatic organisms modify their phenotype (e.g., behaviour or morphology) to reduce their risk of predation. A principal means by which organisms assess predation risk is through chemical cues produced by the predators and/or prey during predation events. Such responses to predation risk can directly affect prey fitness and indirectly affect the fitness of species with which the prey interacts. Accurate assessment of the cue will affect the adaptive nature, and hence evolution, of the phenotypic response. It is therefore, important to understand factors affecting the assessment of chemical cues. Here I examined the effect of the age of chemical cues arising from an invertebrate predator, a larval dragonfly (Anax junius), which was fed bullfrog tadpoles, on the behavioural response (activity level and position) of bullfrog tadpoles. The bullfrog response to chemical cues declined as a function of chemical cue age, indicating the degradation of the chemical cue was on the order of 2–4 days. Further, the decay occurred more rapidly when the chemical cue was placed in pond water rather than well water. These results indicate a limitation of the tadpoles to interpret factors that affect the magnitude of the chemical cue and hence accurately assess predation risk. These findings also have implications for experimental design and the adaptation of phenotypic responses to chemical cues of predation risk.

PEACOR, S.D., J. R. Bence, and C.A. Pfister. The effect of size-dependent growth and environmental factors on animal size variability. Theoretical Population Biology 71(2007):80-94 (2006).

The origin of variation in animal growth rate and body size is not well understood but central to ecological and evolutionary processes. We develop a relationship that predicts the change in relative body size variation within a cohort will be approximately equal to the relative change in mean per unit size growth rate, when only size-dependent factors affect growth. When modeling cohort growth, relative size variation decreased, remained unchanged, or increased, as a function of growth rate-size scaling relationships, in a predictable manner. We use the approximation to predict how environmental factors (e.g., resource level) affect body size variation, and verified these predictions numerically for a flexible growth model using a wide range of parameter values. We also explore and discuss the assumptions underlying the approximation. We find that factors that similarly affect mean growth rate may differently affect size variation, and competition may increase body size variation without changing size-independent relationships. We discuss implications of our results to the choice of growth equations used in models where body size variation is an important variable or output.

PEACOR, S.D., S. Allesina, R L. Riolo, and M. Pascual. Phenotypic plasticity opposes species invasions by altering fitness surface. PLoS Biology 4(11):9 pp. (2006).

Understanding species invasion is a central problem in ecology because invasions of exotic species severely impact ecosystems, and because invasions underlie fundamental ecological processes. However, the influence on invasions of phenotypic plasticity, a key component of many species interactions, is unknown. We present a model in which phenotypic plasticity of a resident species increases its ability to oppose invaders, and plasticity of an invader increases its ability to displace residents. Whereas these effects are expected due to increased fitness associated with phenotypic plasticity, the model additionally reveals a new and unforeseen mechanism by which plasticity affects invasions: phenotypic plasticity increases the steepness of the fitness surface, thereby making invasion more difficult, even by phenotypically plastic invaders. Our results should apply to phenotypically plastic responses to any fluctuating environmental factors including predation risk, and to other factors that affect the fitness surface such as the generalism of predators. We extend the results to competition, and argue that phenotypic plasticity’s effect on the fitness surface will destabilize coexistence at local scales, but stabilize coexistence at regional scales. Our study emphasizes the need to incorporate variable interaction strengths due to phenotypic plasticity into invasion biology and ecological theory on competition and coexistence in fragmented landscapes.

PEACOR, S.D., L. Schiesari, and E.E. Werner. Mechanisms of nonlethal predator effect on cohort size variation: ecological and evolutionary implications. Ecology 88(6):1536-1547 (2007).

Understanding the factors responsible for generating size variation in cohorts of organisms is important for predicting their population and evolutionary dynamics. We group these factors into two broad classes: those due to scaling relationships between growth and size (size-dependent factors), and those due to individual trait differences other than size (size-independent factors; e.g., morphology, behavior, etc.). We develop a framework predicting that the nonlethal presence of predators can have a strong effect on size variation, the magnitude and sign of which depend on the relative influence of both factors. We present experimental results showing that size-independent factors can strongly contribute to size variation in anuran larvae, and that the presence of a larval dragonfly predator reduced expression of these size-independent factors. Further, a review of a number of experiments shows that the effect of this predator on relative size variation of a cohort ranged from negative at low growth rates to positive at high growth rates. At high growth rates, effects of size-dependent factors predominate, and predator presence causes an increase in the scaling of growth rate with size (larger individuals respond less strongly to predator presence than small individuals). Thus predator presence led to an increase in size variation. In contrast, at low growth rates, size-independent factors were relatively more important, and predator presence reduced expression of these size-independent factors. Consequently, predator presence led to a decrease in size variation. Our results therefore indicate a further mechanism whereby nonlethal predator effects can be manifest on prey species performance. These results have strong implications for both ecological and evolutionary processes. Theoretical studies indicate that changes in cohort size variation can have profound effects on population dynamics and stability, and therefore the mere presence of a predator could have important ecological consequences. Further, changes in cohort size variation can have important evolutionary implications through changes in trait heritability.

POTHOVEN, S.A., I. A. Grigorovich, G.L. FAHNENSTIEL, and M.D. Balcer. Introduction of the Ponto-Caspian bloody-red mysis Hemimysis anomala into the Lake Michigan basin. Journal of Great Lakes Research 33:285-292 (2007).

Hemimysis anomala G.O. Sars, 1907, a mysid species native to the Ponto-Caspian region, was discovered during fall 2006 in the Lake Michigan basin. Large numbers of individuals formed aggregations (averaging 1,540 ± 333 individuals/m2) in a shallow docking basin connected to the channel linking Lake Michigan and Muskegon Lake. The population included females (63%), males (35%), and juveniles (2%). The global invasion pattern in H. anomala is similar to that in another Ponto-Caspian peracarid crustacean, Echinogammarus ischnus. As with E. ischnus, the expansion of H. anomala in North America is anticipated.

POTHOVEN, S.A., H.A. VANDERPLEOG, J.F. CAVALETTO, D.M. KRUEGER, D.M. MASON, and S.B. BRANDT. Alewife planktivory controls the abundance of two invasive predatory cladocerans in Lake Michigan. Freshwater Biology 52(doi:10.1111/j.1365-2427.2007.01728.x):561-573 (2007).

1. We sampled along a nearshore transect (10-m bathymetric contour) in Lake Michigan to determine diet, 24-h feeding periodicity, daily ration and food requirements of an invasive fish, the alewife, Alosa pseudoharengus, relative to zooplankton abundance and production. Our objective was to determine whether the alewife controls the abundance of two invasive, predatory cladocerans, Bythotrephes longimanus and Cercopagis pengoi.
2. Bosminidae was the most abundant prey taxon and Chydoridae, Leptodora, Chironomidae and Bythotrephes were the least abundant. Neither Bythotrephes nor Cercopagis were important prey for small alewives (≤100 mm). Bythotrephes was eaten by over 50% of large alewives (>100 mm) and accounted for 10–27% of the diet weight. Cercopagis was eaten by about 30% of the large alewives but only accounted 1% of the diet weight.
3. Food weight in stomachs was highest early in the night for small alewives and lowest at night for large alewives. Chironomidae and large Chydoridae were the preferred prey of small alewives. Bythotrephes and large Chydoridae were the preferred prey for large alewives.
4. Food requirements of alewife were much less than production for most prey taxa, although the consumption of Bythotrephes greatly exceeded production on both dates. Alewives consumed only 3% of Cercopagis production. High selectivity and food requirements of alewife for Bythotrephes, and low selectivity and food requirements for Cercopagis, probably explain the difference in abundance between these two invasive cladocerans at our nearshore site in Lake Michigan.

RAIKOW, D. F., P. F. LANDRUM, and D. F. REID. Aquatic invertebrate resting egg sensitivity to glutaraldehyde and sodium hypochlorite. Environmental Toxicology and Chemistry 26(8):1770-773 (2007).

Ballast tank treatment technologies are currently in development to reduce the risk of acquiring or transporting viable aquatic organisms that could be introduced to ecosystems and become invasive. Aquatic invertebrate resting eggs represent a challenge to such technologies because of morphological and biochemical adaptations to stress that also protect eggs from artificial stressors. To evaluate the potential efficacy of chemical biocides for ballast tank treatment, the present study examined the acute toxicity of glutaraldehyde and sodium hypochlorite on resting eggs of the freshwater cladoceran Daphnia mendotae and marine brine shrimp (Artemia sp.). Glutaraldehyde was toxic to resting eggs of Artemia sp., as indicated by a lethal concentration to 90% of organisms (LC90) of 95% confidence interval (226 ± 10 mg/L). Daphnia mendotae, in contrast, displayed erratic responses to glutaraldehyde. Sodium hypochlorite was similarly toxic to resting eggs of Artemia sp. and D. mendotae, which displayed LC90s of 86.5 ± 3.0 and 78.3 ± 1.6 mg/L, respectively. Burial in sediment protected resting eggs from toxicants. The present results corroborate those from previous investigations of resting egg sensitivity to artificial stressors, supporting the conclusions that resting eggs are less sensitive than other life stages to artificial stressors and that chemical biocide concentrations effective against other life stages may be ineffective against resting stages.

RAIKOW, D. F., D. F. REID, E. R. Blatchley, G. JACOBS, and P. F. LANDRUM. Effects of proposed physical ballast tank treatments on aquatic invertebrate resting eggs. Environmental Toxicology and Chemistry 26(4):717-725 (2007).

Adaptations in aquatic invertebrate resting eggs that confer protection from natural catastrophic events also could confer protection from treatments applied to ballast water for biological invasion vector management. To evaluate the potential efficacy of physical ballast water treatment methods, the present study examined the acute toxicity of heat (flash and holding methods), ultraviolet (UV) radiation (254 nm), and deoxygenation (acute and chronic) on resting eggs of the freshwater cladoceran Daphnia mendotae and the marine brine shrimp Artemia sp. Both D. mendotae and Artemia sp. were similarly sensitive to flash exposures of heat (100% mortality at 70oC), but D. mendotae were much more sensitive to prolonged exposures. Exposure to 4,000 mJ/cm2 of UV radiation resulted in mortality rates of 59% in Artemia sp. and 91% in D. mendotae. Deoxygenation to an oxygen concentration of 1 mg/L was maximally toxic to both species. Deoxygenation suppressed hatching of D. mendotae resting eggs at oxygen concentrations of less than 5.5 mg/L and of Artemia sp. resting eggs at concentrations of less than 1 mg/L. Results suggest that UV radiation and deoxygenation are not viable treatment methods with respect to invertebrate resting eggs because of the impracticality of producing sufficient UV doses and the suppression of hatching at low oxygen concentrations. Results also suggest that the treatment temperatures required to kill resting eggs are much higher than those reported to be effective against other invertebrate life stages and species. The results, however, do not preclude the effectiveness of these treatments against other organisms or life stages. Nevertheless, if ballast tank treatment systems employing the tested methods are intended to include mitigation of viable resting eggs, then physical removal of large resting eggs and ephippia via filtration would be a necessary initial step.

Rao, Y.R., and N. HAWLEY. Interbasin exchange flows in Lake Erie. Proceedings, Sixth International Symposium on Stratified Flows, Perth, Australia, December 11-14, 2006. International Association of Hydraulic Engineering and Research, 245-250 pp. (2006).

Exchange processes between the three basins of Lake Erie relevant to water quality during summer stratified season are discussed in this paper. Currents, water temperature, winds, radiation, and waves were recorded at fixed moorings in Lake Erie during 2004 and 2005. Circulation within and between the basins is studied. The thermal structure and exchange processes during summer stratification and early fall indicates that both barotropic and baroclinic processes influence the exchange flows.

Rao, Y.R., and D.J. SCHWAB. Transport and mixing between the coastal and offshore waters in the Great Lakes: A review. Journal of Great Lakes Research 33:202-218 (2007).

The Laurentian Great Lakes of North America have horizontal scales of hundreds of kilometers and depth scales of hundreds of meters. In terms of coastal dynamics, they behave much like inland seas and exhibit physical processes characteristic of the coastal oceans. The lakes are dynamically similar to the coastal ocean in that their horizontal dimensions are larger than the vertical dimensions, and the principal source of mechanical energy is the wind. The major difference in dynamical processes is that the lakes are enclosed basins and are not connected to the deep ocean. This paper presents an overview of some of the significant aspects of physical processes in the coastal zones of the Great Lakes. The review is based on examples ranging from lake-wide experiments like the International Field Year on the Great Lakes (IFYGL) to several process-oriented coastal boundary layer experiments. The basic circulations in the nearshore zone and coastal boundary layer are summarized. The review concludes with suggestions for future work on the understanding of the physical processes that would have a bearing on lake management in the coastal zones of the Great Lakes.

REID, D.F. Conversion of specific gravity to salinity for ballast water regulatory management. NOAA Technical Memorandum GLERL-139. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 24 pp. (2006).

To reduce the risk of new aquatic species introductions to coastal ecosystem via the ballast tanks of ocean-going ships, both the United States and Canada have established regulatory and/or policy requirements based on assuring that the salinity of incoming ballast water, including residual ballast water, is 30 ppt or greater. However, common shipboard practice for management of ballast water is to determine the specific gravity of the water, not the salinity. Thus there is a technical disconnect between the information the ship typically records and what the regulatory agencies need. In 1981 a new equation of state for seawater was established, including a highly accurate mathematical relationship between density, salinity, temperature, and pressure. The equation is valid for salinity from 2 to 42 (practical salinity) and temperature from -2 to 35oC. The equation of state for seawater was used to calculate a set of tables relating salinity to density and specific gravity, which were then converted into a related series of graphs, presented in this report, that can be used by ship’s crews and regulators alike to convert between salinity and specific gravity.

REID, D.F., R. STURTEVANT, and S.A. POTHOVEN. Calling on the public: Where in the Great Lakes basin is the newest aquatic invader, Hemimysis anomala? Aquatic Invaders 18(1):1-7 (2007).

A new aquatic invader, the bloody-red mysid shrimp (Figure 1), was discovered in the Great Lakes in 2006, but has been confirmed only at two locations (Figure 2). Scientists believe it probably has a wider distribution, but has not been previously reported either because people didn’t recognize it as a new organism, or simply didn’t see it. Hemimysis anomala is difficult to locate because it is nocturnal, preferring to hide in rocky cracks and crevices near the bottom along the shoreline during daylight. However, it also sometimes exhibits a unique swarming behavior, forming small dense reddish-tinged clouds containing thousands of individuals concentrated in one location, usually visible just below the water surface in a shadow zone (Figure 3). This is the basis for a new survey and monitoring program being established which is asking for public assistance in locating other occurrences of this organism.

RUBERG, S.A., S.B. BRANDT, R.W. MUZZI, N. HAWLEY, T. Bridgeman, G.A. LESHKEVICH, J.C. LANE, and T.C. MILLER. A wireless real-time coastal observation network. EOS Transactions 88(28):285-286 (2007).

A new integrated coastal observation system is providing preliminary data from the North American Great Lakes. This system can be implemented in other coastal regions. To date, it has been successfully deployed on Lakes Michigan, Huron, and Erie to make seabed to sea-surface measurements of chemical, biological, and physical parameters, which are transmitted wirelessly through buoys and permanent stations. Called the Real-Time Coastal Observation Network (ReCON), the new system leverages existing networking technology to provide universal access to a wide variety of instrumentation through the use of an underwater Ethernet port server [Austin, 2002]. A team of NOAA engineers and scientists has completed the development and testing of this integrated coastal observation network.

Ruiz, G.M., and D.F. REID. Current state of understanding about the effectiveness of Ballast Water Exchange (BWE) in reducing Aquatic Nonindigenous Species (ANS) introductions to the Great Lakes basin and Chesapeake Bay, USA: Synthesis and analysis of existing information. NOAA Technical Memorandum GLERL-142. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 127 pp. (2007).

This report summarizes the current state of knowledge about ballast water exchange (BWE) as a management strategy by ships to reduce the risk of invasions, with emphasis on two major U.S. ecosystems, the Great Lakes and Chesapeake Bay. Today, most global trade occurs by shipping among ports, creating unintended opportunities for transfer of aquatic species that result in biological invasions. Ships transfer organisms in their ballast tanks and on their hulls. To reduce the risk of invasions from ballast water discharge, estimated annually to exceed 70,000,000 metric tons in the U.S., ships arriving from foreign ports are required to conduct ballast water exchange (BWE) or alternative treatment before discharging ballast. This management strategy became mandatory in the United States for the Great Lakes and upper Hudson River in 1993, and it has been required for ships arriving to the Chesapeake Bay and all other ports since September 2004.

Schuler, L.J., P.F. LANDRUM, and M.J. Lydy. Response spectrum for fluoranthene and pentachlorobenzene for the fathead minnow (Pimephales promelas). Environmental Toxicology and Chemistry 26(1):139-148 (2007).

Internal body residue has been recognized as a potential dose metric for toxicological assessments. This relationship between body residue and biological effects, including both lethal and sublethal effects, is critically important for determining environmental quality in risk assessments. The present study identified the toxic equivalent body residues for fluoranthene (FLU) and pentachlorobenzene (PCBz) associated with mortality, reduced growth, and decreased hatchability in the fathead minnow. The toxic equivalent body residue was defined as the total of the parent compound and the organically extractable metabolites for FLU and of the parent compound only for PCBz, because no biotransformation was measurable. The lethal body residues corresponding to 50% mortality were 0.80 and 1.26 umol/g wet weight for FLU and PCBz, respectively. As expected, residues associated with sublethal effects generally are 2- to 40-fold lower than the lethal residues for FLU and PCBz. Juvenile fish growth was the most sensitive endpoint examined for both compounds. The maximum allowable toxicant residues were 0.02 and 0.43 umol/g wet weight for FLU and PCBz, respectively. The information collected from the present study will permit a greater understanding of residue–response relationships, which will be useful in risk assessments.

Schuler, L.J., P.F. LANDRUM, and M.J. Lydy. Response spectrum of pentachlorobenzene and fluoranthene for Chironomus tentans and Hyalella azteca. Environmental Toxicology and Chemistry 26(6):1248-1257 (2007).

The whole-body residues of pentachlorobenzene (PCBz) and fluoranthene (FLU) in Hyalella azteca and Chironomus tentans were determined for a variety of chronic sublethal effects. The endpoints evaluated for H. azteca included 28-d growth and survival and 42-d growth, survival, and reproduction. Adverse effects to C. tentans also were determined at multiple endpoints including 10-d growth, cumulative pupation and emergence, and reproduction. The lowest-observed-effect residue (LOER) based on whole-body residues associated with growth was consistent between compounds and species tested with concentrations ranging from 0.17 to 0.33 umol/g. For H. azteca, the most sensitive endpoints were growth at 0.23 umol/g and reproduction at 0.11 umol/g for PCBz and FLU, respectively. For C. tentans, the most sensitive endpoints were emergence, development and reproduction at 0.02 umol/g, and development and reproduction at 0.15 umol/g for PCBz and FLU, respectively. Compared to residues associated with acute lethality, the most sensitive sublethal endpoints were approximately 4 and 60 times lower for PCBz and FLU, respectively. The relative consistency of the sublethal endpoints suggests that body residues can be a valuable tool to evaluate bioaccumulation data as part of a risk assessment to predict adverse effects to biota.

STOW, C.A., C.R. Allen, and A.S. Garmestani. Evaluating Discontinuities in Complex Systems: Toward Quantitative Measures of Resilience. Ecology and Society 12(1):26 pp. (2007).

The textural discontinuity hypothesis (TDH) is based on the observation that animal body mass distributions exhibit discontinuities that may reflect the texture of the landscape available for exploitation. This idea has been extended to other complex systems, hinting that the identification and quantification of discontinuities in the distributions of appropriate variables may provide clues to emergent system properties such as resilience. We propose a discontinuity index, based on the vector norm of the full assemblage of observed discontinuities, as a means to quantify and compare this characteristic among systems. We also evaluate four methods to identify the number and location of the most prominent discontinuities. Although results of the four methods are similar, they are not identical, and we conclude that this problem is best addressed with a consistent operationally defined approach in an adaptive inference framework.

STOW, C.A., M.E. Borsuk, and K.H. Reckhow. Chapter 5 - Ecosystem Risk Assessment: The Neuse River Estuary, North Carolina. In Risk Assessment for Environmental Health. M. Robson and W. Toscano (Eds.). John Wiley and Sons, San Francisco, CA, 563-585 (2007).

Students who complete this chapter will be able to: (1) Appreciate the role of models in ecological risk assessment, (2) Recognize the high intrinsic uncertainties in making ecological forecasts, (3) Understand the distinction between science and policy in environmental decision making, and (4) Become familiar with the concept of "adaptive management". Ecosystem risk assessment involves evaluating the current state of an ecosystem, deciding what state the system should be in, and forecasting its future state under alternative management options so that decision makers can choose the management actions that are most likely to attain the desired ecosystem state.

VANDERPLEOG, H.A., T.H. JOHENGEN, P.J. Lavrentyev, C. Chen, G.A. LANG, M.A. Agy, M.H. Bundy, J.F. CAVALETTO, B.J. EADIE, J.R. LIEBIG, G.S. MILLER, S.A. RUBERG, and M.J. McCORMICK. Anatomy of the recurrent coastal sediment plume in Lake Michigan and its impacts on light climate, nutrients, and plankton. Journal of Geophysical Research 112(C03S90, doi:10.1029/2004JC002379):23 pp. (2007).

As part of the Episodic Events Great Lakes Experiment, we sampled total suspended matter (TSM), light climate, nutrients, and plankton along cross-margin transects in southern Lake Michigan during February, March, and April 1998–2000 to capture conditions before, during, and after the occurrence of storm-driven recurrent coastal sediment plumes to define the anatomy of the resuspension events and get insights into their interactions with nutrients and plankton. Variability in timing and strength of winter storms among years led to different timing, intensity, and extent of plumes among years. TSM concentrations in the core of plumes varied between 15 and 30 mg L-1, and photic depth was reduced to ~1 to 2 m, thus potentially seriously limiting phytoplankton growth in plume areas. Total P concentration was highly correlated with TSM and river influence. Chlorophyll concentrations were lower in plume regions than in adjacent areas, in contrast to the relatively constant chlorophyll concentration across the plume predicted by a coupled hydrodynamic and nutrient-phytoplankton-zooplankton model. Contrary to expectation, protozoan microzooplankton (MZ) biomass was not more abundant in the plume than adjacent waters, but was highest in nearshore areas receiving river inflow. Storms affected horizontal distribution of zooplankton. Because of the lower concentrations of phytoplankton in the plume, the plume over the short term had a negative impact on zooplankton during this food-limiting season. Our results combined with those of other EEGLE studies lead us to conclude that storms and storm-driven plumes had a negative effect on the planktonic food web.

Yang, X.-Y., D. Wang, J. WANG, and R.X. Huang. Connection between the decadal variability in the southern ocean circulation and the southern annual mode. Geophysical Research Letters 34(L16604, doi:10.1029/2007GL030526):5 pp. (2007).

Previous studies demonstrated the remarkable upward trend of the Southern Annular Mode (SAM) and Southern Ocean wind stress in association with anthropogenic forcing. An oceanic reanalysis data set is used to investigate the response of the circulation in the Southern Ocean to the decadal variability of SAM. Our results indicate the strengthening and the poleward shift of the northward Ekman velocity as well as the Ekman pumping rate, which led to a corresponding strengthening trend in the Deacon Cell. This strengthening, in turn, intensified the meridional density gradient and the tilting of the isopycnal surfaces. On the interannual time scale, the Antarctic Circumpolar Currents (ACC) transport exhibits a positive correlation with SAM index as seen separately in observations. However, there is no significant trend in the total transport of ACC. Possible reasons are discussed.

You, J., P.F. LANDRUM, T.A. Trimble, and M.J. Lydy. Availability of polychlorinated biphenyls in field-contaminated sediment. Environmental Toxicology and Chemistry 26(9):1940-1948 (2007).

Two chemical approaches, Tenax extraction and matrix solid phase microextraction (matrix-SPME), were evaluated as surrogates to estimate bioavailability of polychlorinated biphenyls (PCBs) from field-contaminated sediment. Aroclor 1254 was the primary contaminant found in sediment from Crab Orchard Lake in Marion, Illinois, USA, and a total of 18 PCB congeners were selected for study. Bioaccumulation was determined by exposing the freshwater oligochaete, Lumbriculus variegatus, to the sediment for 28 d. Differences in the rapidly desorbing fraction of PCBs and fraction desorbed within 6 h, defined by Tenax extraction, accounted for 39 and 31% of the differences among biota-sediment accumulation factor values, respectively. A better relationship (r2= 0.95) was found between the oligochaete PCB body residues and the concentration of PCBs in the rapidly desorbing fraction of sediment. The degree of chlorination and planarity of the PCB congeners affected both desorption and bioaccumulation. The higher chlorine substituted and planar PCBs showed less chemical and biological availability, due to their stronger sorption to sediment, compared to the lower chlorinated and nonplanar PCBs. Accumulation of PCBs by L. variegatus correlated well (r2=0.88) with matrix-SPME fiber concentrations. The ratio of measured body residue to estimated body residue from the pore water concentration measured by matrix-SPME ranged from 0.4 to 1.3 with an average of 0.9. Overall, both Tenax and matrix-SPME approaches were useful surrogates of bioaccumulation for a field-contaminated sediment.

Zaiko, A., S. Olenin, D. Daunys, and T.F. NALEPA. Vulnerability of benthic habitats to the aquatic invasive species. Biological Invasions 9:(doi 10.1007/s10530-006-9070-0):703-714 (2007).

A comparative vulnerability analysis of 16 selected benthic habitat types in the SE Baltic Sea waters and the Curonian lagoon, including Klaipeda strait, was performed using long-term monitoring datasets (1980–2003) and results of several other surveys in the lagoon and the sea. Results indicated that invasive species richness (number of alien species per habitat) in lagoon habitats was significantly higher than in the sea. Habitats formed by artificial rock and stone, sand, mud, and habitats modified by zebra mussel shell deposits appeared to be the most invaded. Highest invasive species richness occurred in habitats with high native species richness indicating that the main factors driving native species distribution (such as favourable physical conditions, habitat alterations generated by human or/and biotic activities) are also driving aquatic invaders. Physical factors distinguished to be the most important for native and invasive species distribution were salinity, depth range (expressed by the maximal and minimal depths difference within a habitat), shallowness of a habitat (expressed by a minimal depth), and availability of a hard substrate.


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