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.     

Risk-based classification and interactive map of watersheds contributing anthropogenic stress to Laurentian Great Lakes coastal ecosystems

We describe development anthropogenic stress indices for coastal margins of the Laurentian Great Lakes basin. Indices were derived based on the response of species assemblages to watershed-scale stress from agriculture and urbanization. Metrics were calculated for five groups of wetland biota: diatoms, wetland vegetation, aquatic invertebrates, fishes, and birds. Previously published community change points of these assemblages were used to classify each watershed as ‘least-disturbed’, ‘at-risk’, or ‘degraded’ based on community response to these stressors. The end products of this work are an on-line map utility and downloadable data that characterize the degree of agricultural land use and development in all watersheds of the US and Canadian Great Lakes basin. Discrepancies between the observed biological condition and putative anthropogenic stress can be used to determine if a site is more degraded than predicted based on watershed characteristics, or if remediation efforts are having beneficial impacts on site condition. This study provides a landscape-scale evaluation of wetland condition that is a critical first step for multi-scale assessments to help prioritize conservation or restoration efforts.     

Ecological data as a resource for invasive species management in U.S. Great Lakes coastal wetlands

The coordinated use of ecological data is critical to the proper management of invasive species in the coastal wetlands of the Laurentian Great Lakes. Researchers and government programs have been increasingly calling for the use of data in management activities to increase the likelihood of success and add transparency in decision making. Web-enabled databases have the potential to provide managers working in Great Lakes coastal wetlands with relevant data to support management decisions. To assess the potential value of these databases to managers in Laurentian Great Lakes states, we surveyed wetland managers to determine their current data usage as well as their future data interests and catalogued the online databases currently available. Surveys were disseminated via email to managers in 56 different organizations overseeing invasive species management efforts in Great Lakes coastal wetlands; 46 responses were included in this analysis. Of the survey respondents, all reported using raw biotic data for decision making, (i.e. presence of target species) but many indicated that they would prefer to incorporate a greater variety of data, as well as more complex information. Our survey found that managers used web-enabled databases, but most databases that we catalogued only provided presence data for wetland biota. We concluded that databases can provide the types of data sought by invasive species managers but have unmet potential to be integrated into responsive management processes.     

Brachionus leydigii (Monogononta: Ploima) reported from the western basin of Lake Erie

Several species of non-indigenous planktonic invertebrates have historically been introduced to the Laurentian Great Lakes. Previous introductions of non-indigenous planktonic invertebrates to the Great Lakes have been crustacean zooplankton, specifically Cladocera and Copepoda. This report documents the first known occurrence of Brachionus leydigii var. tridentatus (Zernov, 1901) in Lake Erie and possibly the first detection of a non-indigenous rotifer species in the Laurentian Great Lakes. The specimen was collected from a U.S. EPA monitoring station in the western basin of Lake Erie on April 4, 2016.     

Large lakes in climate models: A Great Lakes case study on the usability of CMIP5

Large lakes have an impact on regional weather. In addition, they can be both sensitive to and influence regional climate changes. In the climate models that are used to investigate future climate changes, lakes are greatly simplified and sometimes absent. At the regional scale, this can have strong implications for the quality of the model information about the future. Through our work with climate information users in the Laurentian Great Lakes region, we have found that basic credibility of the information requires the underlying climate models simulate lake-atmosphere-land interactions. We are not aware of efforts within the scientific community to make known how individual large lakes are represented in models and how those representations translate to the quality of the data for particular regions. We share our framework for identifying how the Laurentian Great Lakes are represented in the Coupled Model Intercomparison Project (CMIP) version 5 climate models. We found that most CMIP5 models do not simulate the Great Lakes in a way that captures their impact on the regional climate, which is a credibility issue for their projections. We provide a perspective on the usability of CMIP5 for practitioners in the Great Lakes region and offer recommendations for alternative options.     

Annotated Checklist of the Free-Living Copepods of the Great Lakes

An annotated checklist of the free-living copepods of the Laurentian Great Lakes is developed on the basis of published records. Synonymies are included for each species, relating, wherever possible, invalid names in the literature with currently recognized taxonomy. Twelve species of calanoids, six species of planktonic cyclopoids, nine species of benthic/ littoral cyclopoids, and fourteen species of harpacticoids have been reported from the Great Lakes. Ten of the calanoids and four of the cyclopoids are characteristic of limnetic waters. Three calanoids and two planktonic cyclopoids have been reported infrequently and are perhaps accidental occurrences. The composition of the planktonic copepod fauna in most subregions of the Great Lakes is well-known. In contrast, the sampling of benthic/littoral cyclopoids and harpacticoids has been so infrequent that their kinds, areas of occurrence, and relative abundances are still poorly understood.     

Water depth and lake-wide water level fluctuation influence on α- and β-diversity of coastal wetland fish communities

Coastal wetlands in the Laurentian Great Lakes are critical habitats for supporting fish diversity and abundance within the basin. Insight into the coupling of biodiversity patterns with habitat conditions may elucidate mechanisms shaping diverse communities. Within coastal wetlands, water depth as well as fluctuations in lake-wide water levels over inter-annual timescales, both have the potential to influence fish communities. Water level fluctuation can influence fish habitat structure (e.g., vegetation) in Great Lakes coastal wetlands, but it is unclear how water depth and lake-wide water level fluctuations affect fish community composition and diversity. Using β dissimilarity indices and multivariate ordination techniques, we assessed fish community structure among bulrush (Schoenoplectus acutus)-dominated wetlands in Saginaw Bay, Lake Huron, USA. We examined whether community structure was related to wetland water depth at the time of sampling and whether fish communities were more similar among years with similar Lake Huron water levels. Results suggested relatively high levels of both spatial (among wetlands) and temporal (among year) community dissimilarity that was driven primarily by species turnover. Thus, variability in water depths among wetlands and in Lake Huron water levels among years likely both contribute to regional fish diversity. Further, fish abundance and alpha diversity were positively correlated with wetland water depth at the time of sampling. Both climate change and anthropogenic water level stabilization may alter the magnitude and timing of water level fluctuations in the Great Lakes. Our data suggest that these changes could affect local fish community composition and regional fish diversity.     

Distribution of crayfish in the Southern Basin of Lake Michigan and the Greater Chicago Region

Crayfish represent important links in aquatic food webs because they have diverse, omnivorous diets and are an important source of energy for fishes and birds. Crayfish have the ability to increase sediment transport through bioturbation, some are considered ecosystem engineers due to their burrowing habits, and crayfish invasions have been linked to large declines in biodiversity and changes in ecosystem structure and function. Despite their ecological importance and the threats that invasive crayfishes pose, the distribution of crayfishes in the Laurentian Great Lakes is not well studied. Here, we report on four years of intensive crayfish surveys in the southwestern portion of the Lake Michigan Basin, a region with diverse freshwater ecosystems and few previous records of crayfish distribution. From 2015 to 2018, baited minnow traps and SCUBA were used to document the distribution and abundance of crayfish across streams, rivers, inland lakes, and Lake Michigan. Six species of crayfish were captured, including two invasive species. The invaders are the widely distributed and abundant Faxonius rusticus (rusty crayfish) and Procambarus clarkii (red Swamp crayfish), a species early in the invasion phase. Native species were found in fewer habitat types and were less abundant than invasive F. rusticus. Comparing our results to previous sampling showed that native crayfish distribution and diversity have declined at the same time that F. rusticus has spread over recent decades. There is potential for new and recently introduced invaders, such as the red swamp crayfish, to further alter ecosystems.     

Widespread prevalence of hypoxia and the classification of hypoxic conditions in the Laurentian Great Lakes

Aquatic hypoxia within the Laurentian Great Lakes has contributed to various adverse ecological consequences and stimulated research interest in recent decades. An analysis of published peer-reviewed journal articles from 2000 to 2020 demonstrates an increasing trend of studies related to hypoxia in the Laurentian Great Lakes. However, the majority of these studies (78%) focus on Lake Erie and in particular the well-documented hypolimnetic hypoxic conditions that develop in the central basin of Lake Erie. This hypoxic zone is relatively large (up to 1.5 million ha), has substantial ecological effects, and motivates monitoring programs and water quality improvement initiatives. Nonetheless, the hypoxic zone in the central basin of Lake Erie is only one of over twenty documented hypoxic zones in the Laurentian Great Lakes. Moreover, hypoxic conditions in the Great Lakes are quite diverse. Here, we define and characterize a four-fold classification of Great Lakes hypoxic conditions: 1) hypolimnetic hypoxia, 2) over-winter hypoxia, 3) diel hypoxia, and 4) episodic hypoxia. We suggest that Great Lakes research and monitoring programs should seek to more broadly document hypoxic conditions and develop models to predict the temporal and spatial occurrence of hypoxia. Such efforts are particularly timely as future climatic conditions contributing to warmer temperatures, longer and more intense stratified periods, increased spring nutrient loading and more variable allocthonous inputs are expected to exacerbate three of the four hypoxic conditions described for the Great Lakes (hypolimnetic, diel, and episodic hypoxia).     

Influence of river plumes on the distribution and composition of nearshore Lake Michigan fishes

River plumes form in coastal areas where tributaries mix with their receiving waters. Plume waters are enriched with terrestrial-derived nutrients from their watersheds creating hotspots of biological productivity. The biological importance of plumes scales with the size and persistence of the plume; therefore, large, persistent plumes are more important than small, transient plumes. To date, most studies of plumes have focused on assimilation of terrestrial-derived energy by aquatic species or lower-level food web effects, primarily in marine systems. Few studies have described fish communities near plume habitats and compared them to non-plume areas, especially for the numerous small plumes in the Laurentian Great Lakes. Here we demonstrate that small plumes in the main basin of Lake Michigan enhance local primary productivity and influence distribution and abundance of nearshore Great Lakes fishes. We found that plume fish communities were relatively depauperate and did not support higher biological diversity of fishes compared to non-plume areas. However, individual species including rainbow smelt Osmerus mordax, spottail shiner Notropis hudsonius, and white sucker Catostomus commersonii were more abundant around plumes. Our results demonstrate that small plumes in the main basin of Lake Michigan support highly localized hotspots of biological productivity and fish abundance, primarily within 2?km of river mouths.     

Spectral Attenuation and Irradiance in the Laurentian Great Lakes

Optical data collected between 1973 and 1979 are utilized to study spectral attenuation and irradiance in the midlake waters of four Laurentian Great Lakes. Particular attention is given to the photosynthetic available radiation (PAR), its incident spectral distribution, its spectral attenuation, and its qualitative change with depth. Curves are shown illustrating these spectral properties as well as the relationships between PAR and the photosynthetic usable radiation (PUR) for each of the lakes. These curves, along with the included mathematical relationships, enable quantitative estimates to be obtained of incident PAR, subsurface PAR, and subsurface PUR, and qualitative information to be obtained on subsurface irradiance levels for the Laurentian Great Lakes.     

A pound of prevention,plus a pound of cure: Early detection and eradication of invasive species in the Laurentian Great Lakes

Ballast water regulations implemented in the early 1990s appear not to have slowed the rate of new aquatic invasive species (AIS) establishment in the Great Lakes. With more invasive species on the horizon, we examine the question of whether eradication of AIS is a viable management strategy for the Laurentian Great Lakes, and what a coordinated AIS early detection and eradication program would entail. In-lake monitoring would be conducted to assess the effectiveness of regulations aimed at stopping new AIS, and to maximize the likelihood of early detection of new invaders. Monitoring would be focused on detecting the most probable invaders, the most invasion-prone habitats, and the species most conducive to eradication. When a new non-native species is discovered, an eradication assessment would be conducted and used to guide the management response. In light of high uncertainty, management decisions must be robust to a range of impact and control scenarios. Though prevention should continue to be the cornerstone of management efforts, we believe that a coordinated early detection and eradication program is warranted if the Great Lakes management community and stakeholders are serious about reducing undesired impacts stemming from new AIS in the Great Lakes. Development of such a program is an opportunity for the Laurentian Great Lakes resource management community to demonstrate global leadership in invasive species management.     

The Present Status of Research on the Zooplankton and Zoobenthos of the Great Lakes

A brief evaluation of the present status of knowledge concerning the basic ecology of the zooplankton and zoobenthos of the Great Lakes is presented by considering (1) the species of invertebrates that occur in the Great Lakes, (2) how these species are distributed in space and time, and (3) the factors that cause the observed distributions. It is concluded that we are well along at describing what invertebrates occur in the lakes, but there are still major gaps in our knowledge. Regarding distribution, there is now a good data base for describing the distributions of a number of the most important species, but in most cases the results from separate surveys have not been pulled together to develop generalizations with broad application throughout the Great Lakes. Finally, understanding concerning the control of distributions of Great Lakes invertebrates is still at a rudimentary stage, even though such understanding is a basic requirement for evaluating natural and man-induced changes or potential changes in these ecosystems.     

Colonization of the Laurentian Great Lakes by the Amphipod Gammarus tigrinus,a Native of the North American Atlantic Coast

Gammarus tigrinus, whose natural distribution is restricted to the North American Atlantic coast, has been found at numerous localities across the Laurentian Great Lakes. This amphipod was first discovered in Saginaw Bay of Lake Huron in 2002. However, analysis of archived samples and new material collected during 2001–2004 revealed that G. tigrinus is present in all of the Great Lakes. During August 2002, it occurred at an average density of 283 individuals·m⁻² in Saginaw Bay, where it was outnumbered by the resident amphipods G. fasciatus and Hyalella azteca. In terms of frequency of occurrence, G. tigrinus was the second most numerous amphipod in beds of Typha in lower Great Lakes coastal wetlands during July 2004, being outnumbered only by native G. pseudolimnaeus. Gammarus tigrinus has a history of ballast water transfer in Europe and it likely exploited this transport vector during its recent colonization of the Great Lakes.     

Spatial ecology of reintroduced walleye (Sander vitreus) in Hamilton Harbour of Lake Ontario

Many coastal embayments in the Laurentian Great Lakes have been subjected to extensive human physical modification and pollution that has led to the loss of freshwater biodiversity. For example, Hamilton Harbour is a large coastal embayment situated at the western end of Lake Ontario, with a long history of industrial and urban development that has resulted in the loss and degradation of aquatic habitat and the extirpation of several fish species. To restore the fish community in Hamilton Harbour, several attempts have been made to increase apex predator biodiversity by reintroducing native walleye (Sander vitreus). To assess how reintroduced (i.e., stocked) walleye use Hamilton Harbour, we used acoustic telemetry to characterize the residency of individuals within the boundaries of the harbour as well as their seasonal space use, with a focused interest on the spring spawning period. During the 1?yr tracking period tagged walleye spent an average of 357?days (range 135–365?days) within the harbour. Most individuals (12/15) remained within the harbour during the entire spring spawning period, and over half of the tagged fish departed (n?=?7) at the end of summer and beginning of fall. Core use areas appeared to gradually shift more easterly as the seasons progressed from winter to summer. Results from this study indicate that stocked fish are resident within Hamilton Harbour for most of the year, including the reproductive period, which suggests that stocking efforts to re-establish walleye populations may be an effective restoration strategy if recruitment is successful.     

Foreword: Response of beach and dune systems to changing natural and anthropogenic controls

This Special Section brings together 10 papers with a focus on historical and contemporary processes operating on sandy beach and dune systems in the Great Lakes. Three groupings of papers can be recognised, encompassing the Holocene evolution of dune systems in the Great Lakes, processes operating on modern systems, and the impacts of water level changes on processes operating on sandy beaches and dune complexes. While the research is primarily focused on the Laurentian Great Lakes, the results are relevant to sandy beach and dune systems on both fresh water and marine coasts, and to modelling coastal responses to relative sea level rise over the next century.     

Historical changes and current status of crayfish diversity and distribution in the Laurentian Great Lakes

Despite increasing recognition of the importance of invertebrates, and specifically crayfish, to nearshore food webs in the Laurentian Great Lakes, past and present ecological studies in the Great Lakes have predominantly focused on fishes. Using data from many sources, we provide a summary of crayfish diversity and distribution throughout the Great Lakes from 1882 to 2008 for 1456 locations where crayfish have been surveyed. Sampling effort was greatest in Lake Michigan, followed by lakes Huron, Erie, Superior, and Ontario. A total of 13 crayfish species occur in the lakes, with Lake Erie having the greatest diversity (n = 11) and Lake Superior having the least (n = 5). Five crayfish species are non-native to one or more lakes. Because Orconectes rusticus was the most widely distributed non-native species and is associated with known negative impacts, we assessed its spread throughout the Great Lakes. Although O. rusticus has been found for over 100 years in Lake Erie, its spread there has been relatively slow compared to that in lakes Michigan and Huron, where it has spread most rapidly since the 1990s and 2000, respectively. O. rusticus has been found in both lakes Superior and Ontario for 22 and 37 years, respectively, and has expanded little in either lake. Our broad spatial and temporal assessment of crayfish diversity and distribution provides a baseline for future nearshore ecological studies, and for future management efforts to restore native crayfish and limit non-native introductions and their impact on food web interactions.     

Trends in herring gull egg quality over four decades reflect ecosystem state

Egg quality (size, energy density) is important in determining early survival of birds. Here, we examine temporal (1981–2019) trends in herring gull (Larus argentatus) egg volume and energy density at breeding colonies on all five Laurentian Great Lakes. Temporal declines in egg volume were observed at 4/6 colonies on the upper Great Lakes (Lakes Superior, Michigan, Huron). On the lower Great Lakes (Lakes Erie, Ontario, and connecting channels) egg volume declined at 3/8 colonies and increased at one site. Egg energy density (kJ/g of egg contents) declined at 4/6 upper Great Lakes colonies and at 2/8 lower Great Lakes colonies. All of the upper Great Lakes colonies showed declines in either egg volume or energy density, or both, and these declines were related to dietary markers in eggs (fatty acids, stable nitrogen and carbon isotopes). On the lower Great Lakes and connecting channels, declines in egg volume or energy density were related to dietary endpoints in 3/5 instances. An information-theoretic approach indicated that trends in egg volume were best explained at the colony level while egg energy density trends were best explained by lake of origin. Diet-related declines in herring gull egg quality are likely a reflection of broad-scale ecosystem changes limiting aquatic food availability for gulls, particularly on the upper Great Lakes. These changes may be contributing to population declines in herring gulls and other surface-feeding aquatic birds. This study highlights the value of long-term monitoring of wildlife for identifying ecosystem change.     

Pelagic Bird Survey on Lake Ontario Following Hurricane Isabel,September 2003: Observations and Remarks on Methodology

The abundance and dispersion of pelagic waterbirds was measured on Lake Ontario during the aftermath of the storm system generated by Hurricane Isabel, September 2003. The purpose of this study was to determine whether standard shipboard methodologies developed for surveying pelagic seabirds from ships on the ocean are applicable on the Laurentian Great Lakes, and if so whether such surveys may provide information that cannot be acquired from shore-based surveys. The abundance of waterbirds was low in offshore Lake Ontario, but similar to oligotrophic ocean environments. Our results suggest that bird surveys are easy to conduct from Great Lakes research vessels, and are likely to provide information useful for monitoring ecosystem health in the Lakes.