Line transect distance sampling was employed in aerial surveys of double-crested cormorants (Phalacrocorax auritus) along the coasts of Georgian Bay and the North Channel, Lake Huron. A double-observer method was used to estimate detection probability near the transect line (g(0) = 0.724). Detection of cormorants was not consistent but varied based on group size, location (water, land, flying), and season. Probability of detection in the area covered by the survey was often below 0.5. Incorporating both lack of detection on the flight line along with lack of detection over the covered area inherent in distance sampling provided defensible density estimates of free-ranging double-crested cormorants. Most cormorants were detected loafing on shore (land) among the many islands defining this area of the Lake Huron coast. Land detections exceeded the combined detections of birds on the water and flying. Density in 2004 ranged from a peak of 2.30 cormorants per km² (95% CI = 1.72–3.03) in late July to 1.21 cormorants per km² (95% CI = 0.78–1.70) in late August in the sampled areas extending from shore to approximately 20 km offshore. Aerial surveys employing distance sampling can be useful tools in monitoring the distribution and abundance of free-ranging double-crested cormorants and other waterbirds in the Laurentian Great Lakes.

Aerial line transect distance sampling surveys of coastal areas in the North Channel and Georgian Bay, Lake Huron, were conducted to estimate density of double-crested cormorants (Phalacrocorax auritus). Surveys were approximately every two weeks through summer from 2000 to 2005. In each year, density of cormorants declined towards late summer indicating a large scale outward migration of cormorants from Lake Huron. The seasonal pattern of decline differed between the two regions based on a mixed model analysis. Seasonal patterns in apparent fledging patterns may reflect differences between the North Channel and Georgian Bay in nesting phenology, nesting synchrony or some combination of these factors. Density was generally higher in the North Channel relative to Georgian Bay seasonally and during the period 2000–2002 likely reflecting higher per unit area productivity in the North Channel. In the years 2003–2005, density was lower in both regions and similar compared to earlier years of the survey likely reflecting a regime shift that occurred in Lake Huron at that time. The effect of this change was greater in the North Channel than in Georgian Bay as indicated by a greater decline in cormorant density in the North Channel after 2002.

Lake Urmia, the second largest hypersaline lake by area in the world, has fluctuated in salinity over time, but in recent years, it has reached a maximum of 340 g/L. The lake is the main habitat for the endemic Iranian brine shrimp, Artemia urmiana, and is a protected aquatic environment. Efforts have been made by the Iranian government to enhance the diversity of its wildlife. One approach has been to look for a method to reduce the salt content of the lake. We investigate the feasibility of this by first considering the water chemistry of Lake Urmia and then the various technologies used to extract salt from marine and brackish waters. Average concentrations of Na, Mg, K, Ca, Cl, SO₄, and HCO₃ were 125 g/L, 11.3 g/L, 2.63 g/L, 0.55 g/L, 216 g/L, 22.4 g/L, and 1.38 g/L, respectively, and cations and anions were balanced, However, Lake Urmia waters have a ‘very high’ salinity hazard and a high sodium adsorption ratio (SAR). Moreover, the saturation index (SI) for each of the major cations was greater than zero, indicating that the water in Lake Urmia is supersaturated, and precipitation is likely. The extraction of available salts from the lake for the use in petrochemical industries is economically feasible. However, technologies based on removing salts by distillation or reverse osmosis and then using this fresh water to dilute lake salinity are problematic. A better strategy would be better to allow more fresh water to reach the lake rather than creating fresh water through reverse osmosis and distillations processes. While concerns have been raised about the salinity tolerance of A. urmiana, it has successfully tolerated various salinity ranges from 166 to 340 g/L, and so the species is not threatened, unless the lake desiccates. Because the lake is saturated with salts, it seems unlikely that salinity could increase much higher.

To simulate ice and water circulation in Lake Erie over a yearly cycle, a Great Lakes Ice-circulation Model (GLIM) was developed by applying a Coupled Ice-Ocean Model (CIOM) with a 2-km resolution grid. The hourly surface wind stress and thermodynamic forcings for input into the GLIM are derived from meteorological measurements interpolated onto the 2-km model grids. The seasonal cycles for ice concentration, thickness, velocity, and other variables are well reproduced in the 2003/04 ice season. Satellite measurements of ice cover were used to validate GLIM with a mean bias deviation (MBD) of 7.4%. The seasonal cycle for lake surface temperature is well reproduced in comparison to the satellite measurements with a MBD of 1.5%. Additional sensitivity experiments further confirm the important impacts of ice cover on lake water temperature and water level variations. Furthermore, a period including an extreme cooling (due to a cold air outbreak) and an extreme warming event in February 2004 was examined to test GLIM's response to rapidly-changing synoptic forcing.

Algal class biomarkers revealed the importance of diatoms and chlorophytes in the diet of dreissenids (n 18) collected from eastern Lake Erie (2–20 m depths; hard and soft substrate), during summer and fall, from 2003 to 2005. The most prominent biomarkers in dreissenids, typical of August, were fatty acid esters of carotenoids derived from diatoms (monoesters of fucoxanthinol, average 61%) and chlorophytes (diesters of mactraxanthin, average 30%), while non-esterified biomarkers from diatoms, chlorophytes, cryptophytes and cyanobacteria were below 4% of the total. At cool temperatures (June 2003, 13 °C), dreissenids had 84%:12% diatom:chlorophyte biomarkers, but with unseasonably warm temperatures (June 2004, 18 °C) and a nearshore chlorophyte bloom, dreissenids had a biomarker distribution similar to August. Bioconcentration factors in dreissenids relative to phytoplankton from Lake Erie were largest for the biomarkers from diatoms (21 L/g ww) and chlorophytes (29 L/g ww), compared to those from cryptophytes (2 L/g ww) and cyanobacteria (3 L/g ww). Unlike dreissenids (2003), matching pseudofeces (n 6) and sediments (n 16) contained a relatively large percentage of biomarkers for cryptophytes (20% June, 27% August) and cyanobacteria (31% August), suggesting that their low levels in dreissenids represent ingested feces, which are being rejected. Increased shell size (12–27 mm; surrogate for age; 3 sets) corresponded to an increase in diatom biomarkers (from 60 to 73%) but a decrease in chlorophyte biomarkers (from 31 to 17%); biomarker concentrations also decreased significantly (-3000 pmol/g ww/mm) in the most offshore collection, near Buffalo (Oct. 2005).

Land use change is profoundly influencing the environmental resources of the Great Lakes region. In West Michigan, population growth and rapid land use change have resulted in urbanization and a loss in the diversity of green infrastructure that provides a variety of benefits-ecosystem services-to regional residents and visitors. To address these changes in land use and cover in ways that are objective, transparent, and defensible, local policy makers need tools to help inform local and regional land use decisions. An interdisciplinary team, engaged by a regional policy organization, developed one such online tool, the INtegrated Valuation of Ecosystem Services Tool (INVEST). INVEST utilizes static GIS maps, graphs, and tables, to help educate local and regional decision-makers about the underlying values of ecosystem services associated with green infrastructure, particularly those services that do not pass through traditional commercial markets. In this article we provide a general overview of the development of INVEST and examine its current application as an educational tool, including the specific challenges associated with addressing the information gaps.

Cylindrospermopsis raciborskii occurs predominantly in tropical to subtropical freshwaters but appears to be spreading to temperate regions. After the hurricanes of 2005, a bloom of this organism took place in Lake Dauterive and Lake Fausse Pointe in Louisiana. The cyanobacterium dominated the phytoplankton community for three months. Of the three known morphotypes (straight, coiled and spiral) only coiled and spiral were found. In June 2006, 60% of the organisms were of the spiral morphotype but the relative abundance of this morphotype decreased dramatically within the month of June. However, the average density for both morphotypes remained the same until September. Densities (up to 160,000 cells/mL) significantly exceeded the threshold for toxicity. Because the sampled region offers optimal light and nutrient conditions, it is likely that C. raciborskii has been established in this region and future blooms can be expected. Therefore, a monitoring program should be implemented.

A linked 1-dimensional thermal-dissolved oxygen model was developed and applied in the central basin of Lake Erie. The model was used to quantify the relative contribution of meteorological forcings versus the decomposition of hypolimnetic organic carbon on dissolved oxygen. The model computes daily vertical profiles of temperature, mixing, and dissolved oxygen for the period 1987–2005. Model calibration resulted in good agreement with observations of the thermal structure and oxygen concentrations throughout the period of study. The only calibration parameter, water column oxygen demand (WCOD), varied significantly across years. No significant relationships were found between these rates and the thermal properties; however, there was a significant correlation with soluble reactive phosphorus loading. These results indicate that climate variability alone, expressed as changes in thermal structure, does not account for the interannual variation in hypoxia. Rather, variation in the production of organic matter is a dominant driver, and this appears to have been responsive to changes in phosphorus loads.

This study, motivated by a resurgence in Cladophora, investigates changes in the nutrient environment in the littoral zone of Lake Ontario. We measured nutrient concentrations from 2004 to 2008 at two littoral zone (2–12 m) sites on the north shore of Lake Ontario where Cladophora has experienced a resurgence and compared concentrations with data collected in the late 1970s. Spring total phosphorus (TP) and soluble reactive P (SRP) concentrations have significantly declined at these two sites. Furthermore, P loading from the major tributaries to our study sites declined between 1964 and 2008. Upwelling events were not detectably associated with increases in P concentrations at our sites. We conclude that a recent upsurge in nuisance Cladophora, at least at these sites, cannot be explained by deteriorating littoral zone water quality in terms of P concentrations or by changes in catchment loading. For additional context, we also examined trends in coastal (14–20m) and offshore (>50m) nutrients using Environment Canada epilimnetic surveillance data, 1975–2008. Significant declines in TP and SRP concentrations have occurred in north coast waters, concurrent with declines in the offshore. However, nutrient concentrations, notably spring SRP, have not decreased among south coast stations, potentially reflecting greater coastal entrapment of catchment-derived waters. We infer that EC-monitored north coast stations reflect integrated interannual water quality, while south coast stations are more strongly influenced by catchment loading. The effects of higher nutrient concentrations along the south coast, which co-occur with lower water transparency, on benthic algal growth have yet to be determined.

Few active fish spawning grounds have been found in channels connecting the Great Lakes. Here, we describe one near Belle Isle in the Detroit River, part of the channel connecting lakes Huron and Erie. There, in 2005, we collected 1,573 fish eggs, cultured them, and identified the hatched larvae as walleye (Sander vitreus) and white sucker (Catostomus commersoni). Walleye spawning peaked during the week of April 12–19; white sucker spawning peaked on May 10. Average areal rate of egg deposition by walleye and white sucker at this spawning ground in 2005 was 346 and 25 eggs/m², respectively. Our environmental measurements showed that bottom substrates on this spawning ground were largely sand, not optimal for fish reproduction. We hypothesize that reproduction of these fish at this spawning ground could be enhanced by adding rock and gravel substrates for protection of deposited fish eggs and suggest that reproduction by walleye in the Detroit River may add resilience to production of walleye in western Lake Erie.

Hemimysis anomala, a Ponto-Caspian littoral mysid, is an emerging Great Lakes invader that was discovered in Lakes Michigan and Ontario in 2006. Similar to the native mysid Mysis diluviana, Hemimysis exhibits a diel vertical migration pattern but generally inhabits shallower and warmer waters than M. diluviana. Because basic information on the distribution, habitat use, and biology of Hemimysis in the Great Lakes is scarce, the potential for food web disruption by Hemimysis cannot easily be predicted. Preliminary observations indicate widespread invasion of Hemimysis in Lake Ontario. In this study, we confirm the presence of Hemimysis at sites spanning the northern and southern shores of Lake Ontario and the presence of the individuals during winter months. In one horizontal tow in November 2007, over 26,000 individuals were collected with a length range of 4.4 to 9.0 mm and an average caloric density of 611 cal/g wet weight. The most effective methods for sampling Hemimysis were horizontal tows with either a Zooplankton net in the water column or a benthic sled near the lake bottom. Although more quantitative data on the life history and distribution of this species is necessary, our preliminary observations support the prediction that the potential for Hemimysis to impact the nearshore food web in Lake Ontario appears high.

Michigan stream fish and macroinvertebrate community data from multiple sources were combined to conduct a statewide assessment of riverine ecological condition. Using regionally normalized metrics to correct for methodological inconsistencies and natural variation and statistically based scoring criteria, about 50% of all sampled sites were in expected or better ecological condition, 30% were ecologically impaired, and 20% were marginal. Structural Equation Modeling with this regional assessment dataset indicated that land use effects were more important than effects of point-source discharges. Biological metrics appeared to be more sensitive to urban than agricultural land use, and riparian than basin-wide agricultural land use. Invertebrate communities were marginally more sensitive than fish communities to the suite of anthropogenic stressors examined. Using the observed assessment status from sampled sites, Classification and Regression Tree models were used to estimate ecological condition in the state's remaining unsampled river segments. Combining observed and estimated site scores, 25% of the state's river kms were estimated to be impaired, with the Erie and St Clair basins having the highest degree of impairment (52% and 44% of total channel lengths, respectively) and lakes Superior, Michigan, and Huron basins had the lowest degree of impairment at 4%, 21% and 31%, respectively. We argue that correlations between the state of the Great Lakes and the ecological conditions of their tributary systems reflect both direct impact transmission from watershed to receiving waters, and also non-causal correlation due to shared anthropogenic stressors.

Environmental modeling has been an indispensable tool of the Hamilton Harbour restoration efforts, where a variety of data-oriented and process-based models have been used for linking management actions with potential ecosystem responses. In this study, our objective is to develop a biogeochemical model that can effectively describe the interplay among the different ecological mechanisms modulating the eutrophication problems in Hamilton Harbour, Ontario, Canada. First, we provide the rationale for the model structure adopted, the simplifications included, and the formulations used during the development phase of the model. We then present the results of a calibration exercise and examine the ability of the model to sufficiently reproduce the average observed patterns along with the major cause—effect relationships underlying the Harbour water quality conditions. The present modeling study also undertakes an estimation of the critical nutrient loads in the Harbour based on acceptable probabilities of compliance with different water quality criteria (e.g., chlorophyll a, total phosphorus). Our model suggests that the water quality goals for TP (17 µg L^-1) and chlorophyll a concentrations (5–10µg L^-1) will likely be met, if the Hamilton Harbour RAP phosphorus loading target at the level of 142 kg day^-1 is achieved. We also provide evidence that the anticipated structural shifts of the Zooplankton community will determine the restoration rate as well as the stability of the new trophic state in the Harbour.

For decades the Great Lakes have been subject to invasive species introductions through the discharge of ships' ballast water. Several treatment technologies involving physical, chemical, and biological processes have been developed to remove or inactivate organisms in this discharge. Assessing the efficacy of these technologies involves estimating the number of viable propagules in treated discharge relative to untreated controls. For organisms in the 10–50 µm size range, for example, the International Maritime Organization (IMO) mandates that fewer than 10 viable organisms per milliliter may be discharged. To date, however, there is no standard method to assess viability of natural assemblages of organisms in this size group (largely phytoplankton and protozoans) in freshwater environments. We report here on a process of assemblage concentration, staining with fluorescein diacetate (FDA), and microscopic observation as a reliable and efficient method to assess densities of viable freshwater organisms in this size category in ballast discharge. A number of other methods, including digestion with enzymes, flow cytometry, and a variety of vital and mortal stains, were tested and discarded during this vetting process due to inconsistent or ambiguous results.

We compared polychlorinated biphenyl (PCB) congener profiles of embryos of black-crowned night-herons (Nycticorax nycticorax) nesting in an urban-industrialized area of Chicago, Illinois, USA with those of regurgitated food boluses from nestlings and their primary prey. Consistent with previous studies of piscivorous birds, the PCB burden of embryos was shifted towards more heavily chlorinated congeners (those with 6, 7, and 8 chlorines), when compared to prey. The PCB congener profiles for measured and homolog concentrations in alewife (Alosa pseudoharengus) collected from Lake Michigan at the Chicago, Illinois, waterfront, closely resembled that of regurgitated food boluses collected from nestlings at the Lake Calumet colony. Also, alewife from Illinois and regurgitates were not clearly differentiated by the discriminant analyses for measured, proportional, and homolog concentrations. Congener profiles in alewife from the highly contaminated Indiana Ship Canal, which had a much higher PCB burden (geometric average = 1061.7 ng/g ww [95% CI = 648.6–1061.7 ng/g ww]) than did alewife from Illinois (158.1 [135.8–184.5]ng/gww) and regurgitates (212.3 [177.0–254.7]ng/g ww), reflected a less-chlorinated mixture (i.e., Aroclor 1242). These results are consistent with our observations, which indicated that many of the adults of this colony were foraging along the Chicago waterfront, where alewife had lower PCB burdens. Because the congener patterns of the prey differ, the PCB congener profiles can be used to elucidate foraging patterns of colonial piscivorous birds and determine relative risks to exposed populations.

The Eurasian genotype of common reed (Phragmites australis) is one of the most aggressive plant invading North American wetlands. There is, however, little published evidence on establishment patterns of populations along lakes of the St. Lawrence River—Great Lakes watershed. We tested the hypothesis that the recent invasion of Great Lake Saint-François (Québec, Canada) by common reed was facilitated by a dense road system and by an intense residence construction activity along lakeshores. A total of 345 and 2914 reed stands were mapped along lakeshores, and along the road system of the study area, respectively. The probability of finding a reed stand on a lakeshore increases with the proximity of the lake's outlet, and of a paved road, but decreases with the proximity of a residence built since 1990. It is likely that common reed first spread along the road system, and that wind dispersal of seeds then favored the establishment of populations on lakeshores. Our model does not support the hypothesis that residential construction facilitated the establishment of reed stands, probably because the recent residential construction boom occurred essentially in the southern part of the lake, where the number of roadside reed populations is much lower than in the northern part (lower seed rain). The invasion of Great Lake Saint-François shows that the spread of the plant is not restricted to major river or road systems. Large or small lakes, if submitted to intense diaspore pressure, can also be at risk.

We measured concentrations of DDE, total PCBs, and mercury in bald eagle (Haliaeetus leucocephalus) nestlings at three locations in the upper Midwest: Lake Superior, the upper Mississippi River, and the St. Croix River, 2006–2008. We also analyzed trends in concentrations of these contaminants for eagles on the southern shore of Lake Superior, from 1989 to 2008, using the current and previously published data.' Concentrations of DDE in nestling blood plasma samples were greatest on Lake Superior (geometric mean: 16.2 µg/kg, n = 29), whereas concentrations of total PCBs were highest in Mississippi River samples (88.6 µg/ kg, n = 51). Mercury concentrations were highest along the upper St. Croix River (6.81 µg/g wet weight in feathers, n =19). For Lake Superior, DDE concentrations declined significantly in nestling blood plasma samples from 1989 to 2008, an average of 3.0% annually. Similarly, total PCBs in Lake Superior eaglets decreased 4.0% annually from 1989 to 2008, and mercury concentrations in nestling feathers from Lake Superior nests also decreased significantly from 1991 to 2008, 2.4% per year. With the possible exception of mercury on the upper St. Croix River, mean concentrations in 2006–2008 of all three compounds were below levels associated with significant impairment of reproduction for all sites, and reproductive rates at all three sites averaged >1.2 young per occupied territory, which is greater than the rate indicative of a healthy population.

Measurements of the thermal stratification at 3 locations within Fathom Five National Marine Park in Lake Huron, Ontario during the summers of 2006 and 2007 found large oscillations in the position of the thermocline. These oscillations led to considerable variability in the temperature at a given depth, with frequent changes in temperature at a rate of 5 °C per hour, and brief periods where temperatures changed at the rate of 10 °C per hour. The thermal stress due to such fast rates of temperature change has been previously implicated in negative effects on many aquatic organisms. The thermocline was observed to move by as much as 20 m vertically, and had dominant periods of oscillation of 12, 17 and 24 h. The strongest temperature variability occurs in the depth range of 10–20 m, which accounts for 20% of the total lakebed area within Fathom Five. The temperature variability was lowest in deep regions well below the thermocline and at a sheltered area behind a reef. This variability was a ubiquitous feature of the water column of Fathom Five during the summer stratification, and the impact of these frequent short-term thermal fluctuations on benthic and fish habitat is discussed in this note.

Hemimysis anomala (Crustacea, Mysidae) is a recent invader to North America that until now was reported only from the Laurentian Great Lakes and their immediate embayments, along with the St. Lawrence River. In August 2009, we identified Hemimysis in diets of white perch and yellow perch in Oneida Lake, NY. Night time vertical plankton net tows detected Hemimysis at four sites across the lake. Hemimysis in fish diets (5.5– 8.6 mm) were larger than in net tows (2.2–7.0 mm) and reproduction is occurring as some females had brood sacs. This is the first documented introduction of Hemimysis to an inland lake in North America, outside the Great Lakes. Oneida Lake is located 53 river km upstream from Lake Ontario, the nearest known source of Hemimysis. No genetic differences were found between Hemimysis in Oneida Lake and Lake Ontario, indicating this is likely the source of introduction. Several large rapids, locks, and dams separate the two lakes, and as a result the most likely vector of introduction to Oneida Lake is pleasure boat or light commercial traffic via the canal system or overland transport. The presence of Hemimysis in Oneida Lake 3 years after it was first found in Lake Ontario suggests this species may spread rapidly throughout the basin. Despite an intensive monitoring program on Oneida Lake directed at fish, Zooplankton, and limnology, Hemimysis was only detected in fish diets and night time Zooplankton tows, indicating it may go undetected in lakes for some time using traditional daytime net tows.