Diet of Mute Swans in Lower Great Lakes Coastal Marshes

Abstract: During the past 30 years, nonnative mute swan (Cygnus olor) populations have greatly increased, and continue to increase, in the eastern United States and within the lower Great Lakes (LGL) region. As a result, there is much concern regarding impacts of mute swan on native waterfowl, aquatic plants, and marsh habitats. There are presently only limited dietary data for mute swans in North America and none exist for birds in the LGL region. Thus, in 2001, 2002, and 2004 we collected 132 mute swans from LGL coastal marshes in Ontario, Canada, to determine dietary composition and to evaluate 1) seasonal and sex-related variation in adult diets and 2) age-related dietary differences. Adult diets did not differ among years, collection sites, or seasons, but female diets contained more pondweed spp. (Potamogeton spp.) and less slender naiad (Najas flexilis) and common waterweed (Elodea canadensis) than did diets of males. Adult males, adult females, and cygnets had similar diets during summer and autumn. Overall, mute swan diets mainly consisted of above-ground biomass of pondweed spp., muskgrass (Chara vulgaris), coontail (Ceratophyllum demersum), slender naiad, common waterweed, wild celery (Vallisneria americana), and wild rice (Zizania palustris); below-ground parts of wild celery, sago pondweed (Stuckenia pectinatus), and arrowhead spp. (Sagittaria spp.) were eaten infrequently. Comparison of our findings with those of other diet studies suggested considerable dietary overlap between mute swans and several other species of native waterfowl. Thus, we suggest that mute swans have potential to compete with native waterfowl and impact aquatic plants that are important waterfowl foods within LGL coastal marshes. Further, our results can be used to assess which aquatic plant species may be most impacted by foraging activities of mute swans at other important waterfowl stopover and wintering sites in North America. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):726–732; 2008)     

Sediment microbial enzyme activity as an indicator of nutrient limitation in Great Lakes coastal wetlands

1. We compared the extracellular enzyme activity (EEA) of sediment microbial assemblages with sediment and water chemistry, gradients in agricultural nutrient loading (derived from principal component analyses), atmospheric deposition and hydrological turnover time in coastal wetlands of the Laurentian Great Lakes. 2. There were distinct increases in nutrient concentrations in the water and in atmospheric N deposition along the gradient from Lake Superior to Lake Ontario, but few differences between lakes in sediment carbon (C), nitrogen (N) or phosphorus (P). Wetland water and sediment chemistry were correlated with the agricultural stress gradient, hydrological turnover time and atmospheric deposition. 3. The N : P ratio of wetland waters and sediments indicated that these coastal wetlands were N‐limited. Nutrient stoichiometry was correlated with the agricultural stress gradient, hydrological turnover time and atmospheric deposition. 4. Extracellular enzyme activity was correlated with wetland sediment and water chemistry and stoichiometry, atmospheric N deposition, the agricultural stress gradient and the hydrological turnover time. The ratios of glycosidases to peptidases and phosphatases yielded estimates of nutrient limitation that agreed with those based solely on nutrient chemistry. 5. This study, the first to link microbial enzyme activities to regional‐scale anthropogenic stressors, suggests that quantities and ratios of microbial enzymes are directly related to the concentrations and ratios of limiting nutrients, and may be sensitive indicators of nutrient dynamics in wetland ecosystems, but further work is needed to elucidate these relationships.     

The development of ecosystem objectives for the Laurentian Great Lakes

Historically management of human use of ecosystems has been based around engineering and chemical approaches and through the construction of treatment facilities, effluent controls and setting chemical concentrations, both at end of pipe and in the aquatic environment. However, the general continued degradation of many ecosystems shows these approaches alone are insufficient. In the Laurentian Great Lakes the Great Lakes Water Quality Agreement was first signed in 1972 and ratified in 1978 and in 1987 tacitly acknowledged the problems with a chemical only approach by requiring the development of ecosystem objectives in the 1978 agreement. Furthermore, the agreement specifically identified numerical ecosystem objectives in the 1987 agreement. The evolution of ecosystem objectives in the Great Lakes has expanded from the strictly numerical objectives such as production of lake trout and abundance of the amphipod Pontoporeia hoyi. More recent developments in ecosystem objectives have been the inclusion of indicators for wildlife, habitat, human health and stewardship.Prepared as a discussion paper presented to the United Nations Economic Commission for Europe's seminar on an Ecosystems Approach to Water Management (May 27–31, 1991).     

Developing ecosystem objectives for the Great Lakes: policy,progress and public participation

Under the Great Lakes Water Quality Agreement of 1978 between the United States and Canada, as amended in 1987, an ecosystem objective with associated indicators for Lake Superior was adopted, and a commitment was made to develop ecosystem objectives and indicators for each of the other Great Lakes. Building upon a history of activities within the International Joint Commission related to the development of ecosystem indicators for Lake Superior and for mesotrophic waters, a binational Ecosystem Objectives Work Group (EOWG) has been established by the U.S. and Canada and charged with developing ecosystem objectives for the Great Lakes, beginning with Lake Ontario. These objectives are primarily biological in nature, in contrast to chemical objectives. The approach of the EOWG is to identify in sequence: (1) broad ecosystem goals, (2) a suite of objectives whose attainment would ensure achievement of the goals, and (3) one or more measurable indicators of progress toward meeting each objective. Societal values are reflected in the goals and objectives following consultation with competing users of ecosystem resources. Identification of appropriate indicators requires the assistance of technical experts. The experience of the EOWG in developing ecosystem objectives for Lake Ontario illustrates the application of this process.     

Towards defining aquatic ecosystem health for the Great Lakes

The Canada — U.S. Great Lakes Water Quality Agreement defines Areas of Concern as geographic areas that fail to meet the general or specific objectives of the Great Lakes Water Quality Agreement where such failure has caused or is likely to cause impairment of beneficial use or the area's ability to support aquatic life. Impairment of beneficial use is defined by the Agreement as a change in the physical, chemical or biological integrity sufficient to cause any one of 14 designated use impairments. In 1987 the International Joint Commission's Great Lakes Water Quality Board (GLWQB) recommended that criteria be developed to determine when ecosystem conditions have been impacted enough to warrant designation as an Area of Concern and when conditions have improved sufficiently to be delisted. Based on scientific input and policy considerations, the GLWQB adopted, in principle, a set of quantitative and qualitative listing/delisting criteria for each of the 14 use impairments. These criteria can be uniformly applied throughout the basin. Further, the GLWQB recommended future refinement of these criteria based on advances in science and public input.     

Initial Development and Evaluation of a Sediment Quality Index for the Great Lakes Region

A sediment quality index (SQI) based on the Canadian Water Quality Index was developed and applied to the assessment of sediment quality in two Great Lakes Areas Of Concern where metals are the primary contaminants of potential concern, Peninsula Harbour (Lake Superior) and Collingwood Harbour (Lake Huron). The SQI was calculated according to an equation incorporating two elements; scope—the number of variables that do not meet guideline objectives; and, amplitude—the magnitude by which variables exceed guideline objectives. Categorizations of sediment quality were developed based on SQI scores. The robustness of the SQI was evaluated through comparison of the relative rankings of sediment quality in the two test areas with results obtained from principle components analysis (PCA) incorporating reference sites, and calculations of hazard quotients (HQs). Trends and rankings in sediment quality determined by the SQI were similar to those calculated using PCA at both test areas. The HQs also appeared to be good indicators of sediment quality. Both the SQI and HQ methods are based on existing Sediment Quality Guidelines, but the SQI had the added benefit of allowing straightforward integration of multiple contaminants. The SQI and PCA analyses appeared complementary in that the SQI incorporated information on the number of variables exceeding guideline values and the degree to which these guidelines were exceeded. The PCA allowed a simple check of the SQI by relating test conditions to regional background. It is recommended that this analysis be performed concurrently with SQI to ensure that non-anthropogenic sources of contaminants (metals in this case) are not considered as representing an anthropogenic hazard.     

Stratigraphic and dynamic effects of sediment reworking by Great Lakes zoobenthos

Recent sediments of the North American Great Lakes are inhabited by numerous species of macrobenthos which alter the physical and chemical properties of sediments and modify interface transport characteristics. Distributions of such radionuclides as cesium-137, lead-210, and isotopes of plutonium exhibit a zone of constant activity extending down from the sediment-water interface from 1 to 15 cm. Recent studies have confirmed that radiometrically determined mixed depths are consistent with the vertical distribution of oligochaete worms and the amphipod,Pontoporeia hoyi. Generally, 90% of the benthos are contained within the radiometrically defined mixed zone. Where comparisons are possible, rates of sediment reworking by ‘conveyor belt’ species are comparable to or exceed sedimentation rates. Systematic variations in the mixed depth occur within depositional basins with greatest depths tending to be associated with least consolidated, organically rich materials. A quantitative steady-state mixing model accounts satisfactorily for observed radioactivity and heavy metal profiles. Bioturbation appears to be an important process, limiting the resolution with which historical records of particle-associated contaminants may be reconstructed from sediment cores. As bioturbation serves to maintain contact of contaminated sediments with overlying water, this time may also characterize the long-term lake recovery for contaminants removed by burial. As the time varies with location, a mean for an entire lake is not well known, but is on the order of 20 years for Lake Huron. Contribution No. 300 of the Great Lakes Environmental Research Laboratory, Ann Arbor, Michigan.     

Ecosystem integrity in the Great Lakes Basin: an historical sketch of ideas and actions

The concepts of ecosystem and integrity effectively entered the binational political arena in the Great Lakes Basin in the early 1970's. They were brought together explicitly in the statement of the purpose of the 1978 Great Lakes Water Quality Agreement. The 1987 Protocol to that Agreement has helped to specify the practical meaning of ecosystem integrity of the Great Lakes Basin. The proceedings of a binational workshop in 1988, titled An Ecosystem Approach to the Integrity of the Great Lakes Basin in Turbulent Times, helped to clarify the conceptual meaning. An Ecosystem Charter for the Great Lakes-St. Lawrence River Basin was proposed in 1989 to help achieve more thorough implementation of the commitment to ecosystem integrity. The evolutionary emergence of this political concept and related practice is described in the paper.List of abbreviations used in the text CUSIS Canada-U.S. Inter-University Seminar Series - LAA Environmental Lakes Area - EPA Environmental Protection Agency - GLBC Great Lakes Basin Commission - GLC Great Lakes Commission - GLER Great Lakes Ecosystem Rehabilitation - GLFC Great Lakes Fishery Commission - GLSAB Great Lakes Science Advisory Board - GLU Great Lakes United - GLWQA Great Lakes Water Quality Agreement - HASP Heritage Area Security Plan - IBP International Biological Program - IJC International Joint Commission - IZAP Inundation Zone Adaptive Plan - LAMP Lake-wide Management Plan - LLRS Lake Levels Reference Study - MAB Man and the Biosphere program - NEPA National Environmental Policy Act - PLUARG Pollution from Land Use Activities Reference Group - RAP Remedial Action Plan - SCOL Salmonid Communities in Oligotrophic Lakes - SGLFMP Strategic Great Lakes Fishery Management Plan - SPOF Strategic Plan for Ontario Fisheries - UNESCO United Nations Educational, Scientific and Cultural Organization Aquatic Ecosystem Health and Management Society. Symposium at the University of Waterloo, July 23–25, 1990.     

Feasibility study of a Great Lakes bioenergy system

A bioenergy production and delivery system built around the Great Lakes St. Lawrence Seaway (GLSLS) transportation corridor was assessed for its ability to mitigate energy security and climate change risks. The land area within 100 km of the GLSLS and associated railway lines was estimated to be capable of producing at least 30 Mt(dry) yr⁻¹ of lignocellulosic biomass with minimal adverse impacts on food and fibre production. This was estimated to be sufficient to displace all of the coal-fired electricity in Ontario plus more than 620 million L of green diesel (equivalent to 5.3% of diesel consumption in GLSLS provinces). Lifecycle greenhouse gas emissions were 88% and 76% lower than coal-fired power and conventional diesel, respectively. Production costs of $120 MWh⁻¹ for power and up to $30 GJ⁻¹ ($1.1 L⁻¹) for green diesel were higher than current market prices, but a value for low-carbon energy would narrow the price differential.     

Salinity tolerance of Great Lakes invaders

1. The Laurentian Great Lakes are among the most invaded freshwater ecosystems in the world. Historically, the major vector for the introduction of non‐indigenous species (NIS) has been the release of contaminated ballast water via transoceanic ships. Despite regulations implemented in 1993, requiring vessels carrying fresh ballast water to exchange this water with saline ocean water, new reports of invasions have continued. 2. NIS often have a wide environmental tolerance allowing them to adapt to and invade a variety of habitats. It has been hypothesized that NIS with broad salinity tolerance may be able to survive ballast water exchange (BWE) and continue to pose an invasion risk to the Great Lakes. 3. We tested the short‐term salinity tolerance of eight recent invaders to the Great Lakes, specifically three cladocera (Bosmina coregoni, Bythotrephes longimanus, Cercopagis pengoi), two molluscs (Dreissena polymorpha, Dreissena rostriformis bugensis), and one species each of the families Gammaridae, Mysidae and Gobidae (Echinogammarus ischnus, Hemimysis anomala, Neogobius melanostomus) to determine if they could have survived salinities associated with BWE. 4. Overall, short‐term exposure to highly saline water dramatically reduced survival of all species. Two different methods of BWE tested, simultaneous and sequential, were equally effective in reducing survival. Species that survived the longest in highly saline water either possess behavioural characteristics that reduce exposure to adverse environments (valve closure; both Dreissena species) or are reported to have some degree of salinity tolerance in their native region (Echinogammarus). Given that exposure in our trials lasted a maximum of 48 h, and that species in ballast tanks would typically be exposed to saline water for c. 5 days, it appears that BWE is an effective method to reduce the survival of these NIS. These results provide impetus for tightening policy and monitoring of BWE, in particular for ships entering the Great Lakes from freshwater ports.     

Biogenic silica as an estimate of siliceous microfossil abundance in Great Lakes sediments

Biogenic silica concentration (BSi) in sediment cores from the Great Lakes is evaluated as an estimate of siliceous microfossil abundance. A significant linear relationship was found between measured BSi and diatom valve abundance for sediment cores from the Bay of Quinte, Lake Ontario, Lake Erie, Lake Michigan and Lake Superior and between measured BSi and diatom biovolume for Lake Erie, Lake Michigan, and Lake Superior but not for Lake Ontario. Diatom silica predicted from diatom species abundance and an estimated silica content per cell in the Lake Erie cores accounted for 117% and 103% of measured BSi, respectively. By contrast, predicted diatom silica could only account for 28% of measured BSi in the Lake Michigan core and only 25% in the Lake Superior core. A few large diatoms with a large silica content per cell comprised a major portion of predicted diatom silica in all cores. The discrepancy between chemically measured BSi and the silica predicted from diatoms in the Lake Michigan and Lake Superior cores was partially due to the inability of the regression model, used to estimate diatom silica content, to account for different degrees of silicification in the diatom asemblages from the more dissolved silica rich Lake Michigan and Lake Superior.     

Estimating phosphorus retention of existing and restored coastal wetlands in a tributary watershed of the Laurentian Great Lakes in Michigan,USA

Simulation modeling with uncertainty analysis was applied to the question of nonpoint source pollution control through extensive wetland restoration. The model was applied to the Quanicassee River basin, a tributary stream to Saginaw Bay on Lake Huron in northeastern Michigan, USA. An estimate of the role of the existing 695 ha of riverside and lake-side wetlands in the lower Quanicassee River basin suggests that they retain 1.2 metric tons of phosphorus per year (mt P/yr), or 2.5% of the total phosphorus load from the basin. A simple Vollenweider-type model of phosphorus retention by created wetlands, calibrated with 3-years of data from two wetland sites in Midwestern USA, was used to estimate the effect of major wetland restoration in the basin. For a wetland restoration project involving 15% of the Quanicassee River basin or 3,120 ha of wetlands, an estimated 33 mt P/yr could be retained, assuming a proper hydrologic connection between the wetlands and the river. This would represent a reduction of two-thirds of the existing phosphorus load to the Bay from the Quanicassee River basin. Large-scale wetland restoration appears to be a viable management practice for controlling phosphorus and other nonpoint source pollution from entering Saginaw Bay. It is an alternative that meets two major resource goals – developing wetland habitat and controlling pollution to the Great Lakes.     

Aquatic insect emergence in two Great Lakes marshes

This study determined total number, biomass, taxa, and seasonal occurrence of adult aquatic insects emerging from four vegetation zones in one diked and one undiked freshwater coastal marsh on hypereutrophic lower Green Bay, Lake Michigan, USA during the summer of 1984. Floating box traps were placed in open water, sparse emergent, dense emergent, and wet meadow vegetation zones in each marsh. Insects were collected during 20 24-hour periods, each four days apart, from June 11 to August 26. Two-way ANOVA was used to test differences in number and biomass of insects between marshes and among vegetation zones. Polynomial regression was used to evaluate seasonal emergence patterns. More insects, insect biomass, and insect taxa were found in the diked marsh, especially during the first half of the sampling period. Damselflies were much more abundant in the diked marsh. Most insects and insect biomass were found in the sparse emergent vegetation zone of both marshes. The emerging insect community in the diked marsh appears enhanced by its separation from the hypereutrophic and turbid waters of lower Green Bay.     

Parasites of Aquatic Exotic Invertebrates: Identification of Potential Risks Posed to the Great Lakes

Exotic species typically lose most of their associated parasites during long-distance spread. However, the few parasites that are co-introduced may have considerable adverse impacts on their novel hosts, including mass mortalities. We present a comprehensive inventory of parasites known to infect 38 species of exotic invertebrates established in the Great Lakes, as well as 16 invertebrate species predicted to arrive in the near future, all of them crustaceans. Based on a literature analysis, we identified a total of 277 parasite taxa associated with the examined invertebrates in their native ranges and/or invaded areas. Of these parasites, 56 species have been documented to cause various pathologies in their intermediate or final hosts, with humans and fishes being the most frequently affected host categories. Potentially harmful parasites were identified in 61% of the invaders for which published information was retrieved (in their ranges outside of the Great Lakes), with molluscs and crustaceans hosting the highest numbers of such parasites. The results of our study provide a baseline for further assessment and management of the parasitological risks posed by exotic species to the Great Lakes.     

Effects of Habitat on Mallard Duckling Survival in the Great Lakes Region

Abstract: Habitat provides food and shelter resources for prefledgling waterfowl and thus plays a critical role in their growth, development, and survival. However, few studies have examined whether and how particular elements of habitat affect duckling survival. We investigated relationships of duckling survival rates with distance of overland travel, wetland vegetation composition, water permanency, and surrounding upland vegetation for 116 mallard (Anas platyrhynchos) broods in the Great Lakes region from 2001 to 2003. We found that the probability, on hatch day, that a mallard duckling will survive to 55 days was positively related to the proportion of wetland area that was vegetated and negatively related to the proportion of forest cover within 500 m of duckling locations. We found little support for relationships between duckling survival rates and the proportions of grasslands or seasonal wetlands or to distances traveled overland by broods. Our results suggest that conservation groups and wildlife managers in the Great Lakes region can improve mallard duckling survival rates by managing for, creating, and protecting vegetated wetlands and focusing efforts within lightly-forested areas.     

Contaminant Trends in Freshwater Fish from the Laurentian Great Lakes: A 20-Year Analysis

Although dietary concerns of Laurentian Great Lakes (GL) fish focus on the risk from persistent bioaccumulative toxicant (PBT) contaminants, fish are also an important source of nutrients beneficial to human health such as polyunsaturated fatty acids (e.g., eicosapentanoic acid and docosahexanoic acid). This study presents PBT trend data from the GL tribal fisheries over the past 20 years. PBT contaminants (282 analytes) from fillet portions of lake trout and whitefish were analyzed for trending patterns from 1992 to 2011 and are reported on five of the ATSDR/USEPA Great Lakes biomonitoring legacy contaminants (Hg, ΣDDE, ΣDDT, HCB, mirex, and ΣPCBs), two of the optional biomonitoring PBTs (toxaphene and Σdioxins/furans) and PCB 153 as a specific congener marker. Similar to other recent reports our data indicate that most PBT contaminant concentrations in the GL biota have decreased, which may indicate progress in reducing environmental emissions. Our research confirms that all contaminants demonstrate significant declines except Hg and toxaphene. Both of those remained constant after correcting for known independent factors of age, lipid, and size. These results are potentially encouraging and may provide useful data for the long distance and perhaps global influences of PBTs on the safety of fish consumption.