Perchlorate in environmental waters of the Laurentian Great Lakes watershed: Evidence for uneven loading

A database of nearly 500 analyses of perchlorate in water samples from the Laurentian Great Lakes (LGL) watershed is presented, including samples from streams, from the Great Lakes and their connecting waters, with a special emphasis on Lake Erie. These data were assessed to test an earlier hypothesis that loading of perchlorate to the LGL watershed is relatively uniform. Higher perchlorate concentrations in streams in more developed and urban areas appear to indicate higher rates of loading from anthropogenic sources in these areas. Variable perchlorate concentrations in samples from Lake Erie indicate transient (un-mixed) conditions, and suggest loss by microbial degradation, focused in the central basin of that lake. Interpretation of the data included estimation of annual loading by streams in various sub-watersheds, and simulations (steady state and transient state) of the mass balance of perchlorate in the Great Lakes. The results suggest uneven loading from atmospheric deposition and other sources.     

Metrics of ecosystem status for large aquatic systems – A global comparison

We identified an objective set of 25 commonly available ecosystem metrics applicable across the world's large continental freshwater and brackish aquatic ecosystem. These metrics measure trophic structure, exploited species, habitat alteration, and catchment changes. We used long-term trends in these metrics as indicators of perturbations that represent an ecosystem not in homeostasis. We defined a healthy ecosystem as being in a homeostatic state; therefore, ecosystems with many changing trends were defined as more disturbed than ecosystems with fewer changing trends. Healthy ecosystems (lakes Baikal, Superior, and Tanganyika) were large, deep lakes in relatively unpopulated areas with no signs of eutrophication and no changes to their trophic structure. Disturbed ecosystems (lakes Michigan, Ontario, and Victoria) had shallow to moderately deep basins with high watershed population pressure and intense agricultural and residential land use. Transitioning systems had widely varying trends and faced increasing anthropogenic pressures. Standardized methodologies for capturing data could improve our understanding of the current state of these ecosystems and allow for comparisons of the response of large aquatic ecosystems to local and global stressors thereby providing more reliable insights into future changes in ecosystem health.     

Researcher disciplines and the assessment techniques used to evaluate Laurentian Great Lakes coastal ecosystems

The Laurentian Great Lakes of North America have been a focus of environmental and ecosystem research since the Great Lakes Water Quality Agreement in 1972. This study provides a review of scientific literature directed at the assessment of Laurentian Great Lakes coastal ecosystems. Our aim was to understand the methods employed to quantify disturbance and ecosystem quality within Laurentian Great Lakes coastal ecosystems within the last 20 years. We focused specifically on evidence of multidisciplinary articles, in authorship or types of assessment parameters used. We sought to uncover: 1) where Laurentian Great Lakes coastal ecosystems are investigated, 2) how patterns in the disciplines of researchers have shifted over time, 3) how measured parameters differed among disciplines, and 4) which parameters were used most often. Results indicate research was conducted almost evenly across the five Laurentian Great Lakes and that publication of coastal ecosystems studies increased dramatically ten years after the first State of the Great Lakes Ecosystem Conference in 1994. Research authored by environmental scientists and by multiple disciplines (multidisciplinary) have become more prevalent since 2003. This study supports the likelihood that communication and knowledge-sharing is happening between disciplines on some level. Multidisciplinary or environmental science articles were the most inclusive of parameters from different disciplines, but every discipline seemed to include chemical parameters less often than biota, physical, and spatial parameters. There is a need for an increased understanding of minor nutrient, toxin, and heavy metal impacts and use of spatial metrics in Laurentian Great Lakes coastal ecosystems.     

Canada's national aquatic biological specimen bank and database

Long-term systematic storage of environmental specimens has become an important component of formal environmental monitoring programs in many countries. In 1977, the Contaminants Surveillance Program (CSP) began in the Great Lakes Basin. In support of the CSP, Fisheries and Oceans Canada began archiving fish tissue samples and created the Great Lakes Fisheries Specimen Bank (GLFSB). In 2006, responsibility for the GLFSB was transferred to Environment Canada and it was renamed the National Aquatic Biological Specimen Bank (NABSB). The new name better reflects the current contents and purpose of the specimen bank which now supports Canada's Chemicals Management Plan (CMP). The NABSB employs standardized banking protocols, computerized sample tracking, maintenance of all data and metadata associated with each specimen, and modern storage equipment situated in a dedicated facility at the Canada Centre for Inland Waters in Burlington, Ontario. Since 1977, specimens from the NABSB have contributed to more than 60 scientific publications, reports, and/or book chapters on the status, trends, and bioaccumulation of metals and various organic contaminants such as PCBs, dioxins, furans, and aromatic hydrocarbons, in aquatic ecosystems. Collection and archiving of specimens in the NABSB continues such that the specimen bank currently holds more than 52,000 samples from 18,749 specimens of top predator fish, forage fish, plankton, and other invertebrates collected over 32 years of environmental monitoring in the Canadian waters of the Great Lakes and beyond.     

Evaluation of sea lamprey-associated mortality sources on a generalized lake sturgeon population in the Great Lakes

Lake sturgeon populations in the Laurentian Great Lakes experience two age-specific mortality sources influenced by the sea lamprey Petromyzon marinus control program: lampricide (TFM) exposure-induced mortality on age-0 fish and sea lamprey predation on sub-adults (ages 7–24). We used a generic age-structured population model to show that although lampricide-induced mortality on age-0 lake sturgeon can limit attainable population abundance, sea lamprey predation on sub-adult lake sturgeon may have a greater influence. Under base conditions, adult lake sturgeon populations increased by 5.7% in the absence of TFM toxicity if there was no change in predation; whereas, a 13% increase in predation removed this effect, and a doubling of sea lamprey predation led to a 32% decrease in adult lake sturgeon. Our estimates of lake sturgeon abundance were highly dependent on the values of life history and mortality parameters, but the relative impacts of ceasing TFM treatment and increasing predation were robust given a status quo level of predation. The status quo predation was based on sea lamprey wounding on lake sturgeon, and improvements in this information would help better define tradeoffs between the mortality sources for specific systems. Reduction or elimination of TFM toxicity on larval lake sturgeon, while maintaining TFM toxicity on larval sea lamprey, can promote lake sturgeon restoration and minimize negative impacts on other fish community members.     

Contribution of manipulable and non-manipulable environmental factors to trapping efficiency of invasive sea lamprey

We identified aspects of the trapping process that afforded opportunities for improving trap efficiency of invasive sea lamprey (Petromyzon marinus) in a Great Lake's tributary. Capturing a sea lamprey requires it to encounter the trap, enter, and be retained until removed. Probabilities of these events depend on the interplay between sea lamprey behavior, environmental conditions, and trap design. We first tested how strongly seasonal patterns in daily trap catches (a measure of trapping success) were related to nightly rates of trap encounter, entry, and retention (outcomes of sea lamprey behavior). We then tested the degree to which variation in rates of trap encounter, entry, and retention were related to environmental features that control agents can manipulate (attractant pheromone addition, discharge) and features agents cannot manipulate (water temperature, season), but could be used as indicators for when to increase trapping effort. Daily trap catch was most strongly associated with rate of encounter. Relative and absolute measures of predictive strength for environmental factors that managers could potentially manipulate were low, suggesting that opportunities to improve trapping success by manipulating factors that affect rates of encounter, entry, and retention are limited. According to results at this trap, more sea lamprey would be captured by increasing trapping effort early in the season when sea lamprey encounter rates with traps are high. The approach used in this study could be applied to trapping of other invasive or valued species.     

Interspecific differences in omega-3 PUFA and contaminants explain the most variance in suggested Great Lakes’ fish consumption when risks/benefits are considered together

Contaminants and essential omega-3 fatty acids were analyzed in the fillets of 15 fish species from lakes Superior and Huron in order to estimate the risks and benefits of fish consumption. Additionally, literature data from lakes Ontario and Erie fish were used to provide an overall assessment for 24 fish species from the Canadian waters of the Great Lakes. The consumption advisory (based on contaminant levels) and EPA + DHA content (eicosapentanoic + docosahexanoic acid) were considered as a health risk and a health benefit, respectively.The differences in the risks and benefits of fish consumption were driven more by species than lake, indicating that within the Great Lakes advisories can focus on species rather than lakes to provide balanced risk-benefit estimates. Salmonines and coregonines had the highest EPA + DHA content; their mean EPA + DHA content ranged from 641 to 748 mg 100 g⁻¹ in salmonines, and from 340 to 728 mg 100 g⁻¹ in coregonines. The mean EPA + DHA content in Perciformes and Esociformes was 157–239 mg 100 g⁻¹ and 199–244 mg 100 g⁻¹, respectively. The species-specific consumption advisories were the most stringent for salmonines in all the lakes. For salmonines, the lake-specific advisories were the most stringent in lakes Ontario and Erie, although differences among lakes were small, indicating similar risks across all four lakes. Adherence to local species- and length-specific consumption advisories, in tandem with considering information on nutritional content, leads to evidence-based decisions regarding the optimum balance between risk and benefit with respect to fish consumption.