Corlis W. West

Development and evaluation of test methods for benthic invertebrates and sediments: Effects of flow rate and feeding on water quality and exposure conditions

In order to ensure among-laboratory comparability in the results of sediment toxicity tests, it is necessary to characterize the influence of variations in test regimes on organism responses and exposure conditions. The objective of these studies was to develop and document an optimized combination of overlying water renewal (flow) and feeding rates for sediment tests with three commonly used benthic species (midges, Chironomus tentans; amphipods, Hyalella azteca; oligochaetes, Lumbriculus variegatus). Optimal conditions were defined by a number of chemical and biological considerations including: (1) flow rate through the system, (2) amount of food added, (3) acceptable responses (survival, growth, reproduction) of the organisms over the course of a 10-day test, and (4) maintenance of an adequate concentration of dissolved oxygen in overlying water. The goal was to minimize factors (1) and (2), while maximizing criteria (3) and (4). The major reason for minimizing (1) and (2) was the concern that excessive water flow or addition of food could reduce exposure of the test organisms to sediment-associated contaminants. To evaluate this, interstitial (pore) water concentrations of contaminants (ammonia, zinc, copper, dieldrin) were measured over the course of 10 day tests conducted with a number of different sediments under various flow and feeding regimes. The different combinations of flow/feeding had variable effects upon pore water concentrations of contaminants; for example under our optimized regime, in some instances slight decreases in interstitial water contaminant concentrations were observed, whereas in other cases contaminant concentrations remained constant or even increased. Overall, the use of minimal water renewal and feeding rates should result only in small changes in exposure of benthic organisms to contaminants in pore water over the course of 10-day tests.

Seasonal toxicity of ammonia to five fish and nine invertebrate species

Ammonia is a widely distributed chemical found in surface waters. Its toxicity to aquatic life is principally due to the un-ionized (NH3) form. An extensive review on ammonia toxicity to aquatic life has been recently compiled by the US EPA with most information consisting of fish test values and limited data available for aquatic plants and invertebrates. Invertebrates were found to be generally more tolerant to ammonia than were fishes. This laboratory study is part of a larger evaluation in assessing the impact of ammonia nitrogen in outdoor experimental streams at and above derived water quality criteria concentrations. Primary objective for this laboratory study was to determine the relative sensitivity of un-ionized ammonia to fish and invertebrates in river water at ambient seasonal temperatures.

Integrated assessment of contaminated sediments in the lower Fox River and Green Bay, Wisconsin.

Samples of sediment and biota were collected from sites in the lower Fox River and southern Green Bay to determine existing or potential impacts of sediment-associated contaminants on different ecosystem components of this Great Lakes area of concern. Evaluation of benthos revealed a relatively depauperate community, particularly at the lower Fox River sites. Sediment pore water and bulk sediments from several lower Fox River sites were toxic to a number of test species including Pimephales promelas, Ceriodaphnia dubia, Hexagenia limbata, Selenastrum capricornutum, and Photobacterium phosphorum. An important component of the observed toxicity appeared to be due to ammonia. Evaluation of three bullhead (Ictalurus) species from the lower Fox River revealed an absence of preneoplastic or neoplastic liver lesions, and the Salmonella typhimurium bioassay indicated relatively little mutagenicity in sediment extracts. Apparent adverse reproductive effects were noted in two species of birds nesting along the lower Fox River and on a confined disposal facility for sediments near the mouth of the river, and there were measurable concentrations of potentially toxic 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), and planar polychlorinated biphenyls (PCBs) both in the birds and in sediments from several of the study sites. Based on toxic equivalency factors and the results of an in vitro bioassay with H4IIE rat hepatoma cells, it appeared that the majority of potential toxicity of the PCB/PCDF/PCDD mixture in biota from the lower Fox River/Green Bay system was due to the planar PCBs. The results of these studies are discussed in terms of an integrated assessment focused on providing data for remedial action planning.

Comparison of the relative sensitivity of three benthic invertebrates to copper-contaminated sediments from the Keweenaw Waterway

The Keweenaw Peninsula in northern Michigan was once a major copper mining area and these mining activities were responsible for depositing tons of tailings in and around the Keweenaw Waterway. In recent years there has been concern about possible toxic effects of the contaminated sediments on aquatic communities in the system. In the fall of 1990, sediments were collected from various locations along the Waterway. Ten-day tests were conducted with the samples using three species of benthic invertebrates that have been proposed as suitable for evaluating the toxicity of freshwater sediments: Hyalella azteca (amphipods), Chironomus tentans (chironomids) and Lumbriculus variegatus(oligochaetes). A number of sediments were toxic to one or more of the three species and, in general, there was good agreement among the tests with regard to identifying toxic samples. Unexpectedly, the relative sensitivity of the three species to the test sediments was not accurately predicted from water-only copper exposures. This indicates that factors modifying exposure, such as different lifestyles and/or varying sensitivity to physico-chemical characteristics of sediments can influence results of sediment toxicity tests.

The Quagga Mussel Invades the Lake Superior Basin

ABSTRACT Prior studies recognized the presence of a single dreissenid species in Lake Superior—the zebra mussel Dreissena polymorpha. However, taxonomic keys based on traditional shell morphology are not always able to differentiate dreissenid species with confidence. We thus employed genetic and morphological analyses to identify dreissenids in a major river-embayment of Lake Superior—the lower St. Louis River/Duluth-Superior Harbor—during 2005–2006. Our results revealed the presence of a second dreissenid species—the quagga mussel D. bugensis (alternatively known as D. rostriformis bugensis). Both species occurred in mixed clusters, in which zebra mussels outnumbered quagga mussels (20–160:1). The largest quagga mussel collected in 2005 was 26.5 mm long and estimated to be two years old, suggesting that the initial introduction occurred no later than 2003. Further monitoring is necessary to determine whether the quagga mussel will colonize Lake Superior. Our results indicate that the coupling of conventional morphological and molecular approaches is essential for monitoring dreissenid species.

HYDROMORPHIC DETERMINANTS OF AQUATIC HABITAT VARIABILITY IN LAKE SUPERIOR COASTAL WETLANDS

Despite the recognized importance of wetlands as habitat for fishes and the growing need to assess and manage human impacts on that habitat, there is little information on patterns and variability of habitat within Great Lakes coastal wetlands. Our goal was to describe wetland aquatic habitat patterns and the natural factors that organize them as a step towards developing habitat assessment schemes and identifying experimental design elements for future synoptic surveys. We analyzed data on aquatic vegetation structure, water chemistry, and water movement (inferred from gypsum plug dissolution) in relation to hydrology and morphology in inundated segments of ten relatively un-impacted coastal marshes of western Lake Superior. Spatial differences in aquatic habitat within wetlands were as large or larger than differences among wetlands, and habitat patterns were strongly associated with morphology and hydrology. Back-bay segments tended to have greater vegetation cover and structural complexity and lower levels of water movement, and they were prone to high water temperatures and low dissolved oxygen levels in wetlands having little seiche activity. Increasing seiche inputs tended to homogenize habitat elements among wetland segments, while increasing tributary inputs tended to increase spatial variability. Patterns in emergent vegetation differed from patterns in submerged/floating vegetation, and different assessment metrics may be needed for different plant zones. Segment-scale sampling schemes like those used in this study have the potential to elucidate habitat patterns within inundated portions of wetlands with a reasonable level of effort. Human impacts on coastal wetland fish habitat must be interpreted in the context of natural spatial heterogeneity as structured by wetland morphology and magnitude of seiche and tributary inputs.

Hydrology and nutrient effects on food-web structure in ten lake superior coastal wetlands

We examined the effects of hydrology and nutrients on the food webs of ten coastal wetlands on Lake Superior, using published stable isotope food web data for three wetlands and original data from seven additional systems in order to span regional hydrologic and nutrient enrichment gradients. We used a dual-source isotope mixing model to estimate the proportion of carbon in fish that originated from planktonic versus periphytic invertebrates, and we related carbon source to 1) nutrient enrichment, 2) hydraulic residence time, and 3) an index of nutrient loading that incorporates residence time and nutrient concentrations. There was no relationship between nutrient enrichment and the proportion of planktonic versus periphytic C in fish. Proportion of planktonic C in fish increased significantly with hydraulic residence time (F = 5.68, R2 = 0.42, p = 0.044). Riverine wetlands generally had lowest proportions of planktonic C in fish, dendritic wetlands were intermediate, and lagoon wetlands had highest proportions. A regression between the loading index and planktonic C in fish was an improvement over the residence time regression (F = 11.7, R2 = 0.59, p = 0.009). We conclude that coastal wetland food webs are strongly affected by hydrology and further by nutrient enrichment. This work has implications for the development of food web-based ecological indicators of nutrient enrichment and the use of hydrology as a classification factor in the prediction of nutrient effects on food webs.

Benthic Versus Planktonic Foundations of Three Lake Superior Coastal Wetland Food Webs

Abstract The structure of aquatic food webs can provide information on system function, trophic dynamics and, potentially, responses to anthropogenic stressors. Stable isotope analyses in a Lake Superior coastal wetland (Allouez Bay, WI, USA) revealed that the food web was based upon carbon fixed by phytoplankton. We report analyses of two Lake Superior coastal wetland food webs not based upon plankton, indicating that Allouez Bay is not the prototype. In Lost Creek and West Fish Creek wetlands (WI, USA), upper trophic levels appear to be supported by benthic, rather than planktonic, food web pathways. Also, zooplankton in Lost Creek and West Fish Creek wetlands are enriched in 13 C relative to periphyton, rather than 13 C-depleted as reported in most other systems. This appears to be a consequence of zooplankton feeding on detrital seston that is 13 C-enriched relative to phytoplankton. We suggest possible causes for the observed differences in food web structure among these wetlands, including hydrologic differences among the systems, and responses to nutrient enrichment among the dominant forms of primary producers, similar to those described in lakes.

Equilibrium partitioning as the basis for an integrated laboratory and field assessment of the impacts of DDT, DDE and DDD in sediments

Many of the most biologically productive portions of streams are backwater areas which support large populations of benthic macroinvertebrates. The sediments in these locations and their associated macroinvertebrate communities are frequently subjected to chemical inputs and physical perturbations. Historically, assessment of the effects of contaminants in sediments have emphasized chemical analyses and either laboratory toxicity tests or in-stream monitoring of benthic macroinvertebrate community structure. However, combining the chemical and biological approaches provides a more powerful assessment technique. Such an integrated approach, combining laboratory water-only and sediment toxicity tests with Hyalella azteca and Chironomus tentans, field surveys of benthic macroinvertebrate community structure and evaluation of chemical data using equilibrium partitioning theory was used to assess the effects of DDT, DDE and DDD (collectively termed DDTR) in the sediments of the Huntsville Spring Branch-- Indian Creek (HSB--IC) stream system in the southeastern USA. Benthic macroinvertebrate populations in the HSB--IC system still appear to be adversely affected by DDTR residues within the sediments even though DDT discharges to the stream were stopped over 20 years ago and a major remediation project was completed in the late 1980s. This conclusion is based on a weight of evidence approach which incorporates (1) the observed sediment toxicity to C. tentans and H. azteca in laboratory tests, (2) the identification of DDTR as the likely cause of effects observed during laboratory toxicity tests, (3) the absence of appropriate sensitive species from groups such as the Ephemeroptera, Plecoptera, Trichoptera and Amphipoda, (4) the presence of reduced numbers of both total individuals and species of chironomids and oligochaetes relative to nearby streams not contaminated by DDTR and (5) the observed distribution of benthic macroinvertebrates in relation to organic carbon-normalized concentrations of DDTR and equilibrium partitioning-based predicted sediment toxic units of DDTR

Status of Non-Indigenous Benthic Invertebrates in the Duluth-Superior Harbor and the Role of Sampling Methods in Their Detection

ABSTRACT As part of a study to develop recommendations for non-indigenous species (NIS) monitoring in Great Lakes areas at risk of invasion, we conducted intensive sampling in the Duluth-Superior Harbor and lower St. Louis River in 2005 and 2006. Of the ∼240 benthic invertebrate taxa identified, 19 were non-indigenous, including 8 first detection records for this system: New Zealand mud snail Potamopyrgus antipodarum; African/Asianorigin cladoceran Daphnia lumholtzi; Eurasian-origin amphipod Echinogammarus ischnus; Eurasian-origin bivalves Dreissena bugensis, Pisidium henslowanum and Pisidium supinum; and possibly range expanding oligochaetes Paranais frici and Pristina acuminata. Dreissenids were by far the most abundant NIS. Several other NIS were also common, but others were detected in only a few of the >200 samples taken. Non-indigenous amphipods and Dreissena were most frequently detected in sweep net and colonization plate samples of littoral vegetation, while NIS oligochaetes, gastropods, and non-dreissenid bivalves were most frequently detected in ponar and bottom sled samples of sediments. Our findings confirm that this major shipping port remains a NIS “hotspot” and emphasize that regular surveys covering a range of habitats with multiple sampling gears and thorough taxonomic effort are needed to detect and monitor non-indigenous species.