Donna R. Kashian

A Comparison of Macroinvertebrates of Two Great Lakes Coastal Wetlands: Testing Potential Metrics for an Index of Ecological Integrity

The macroinvertebrates of two northern Lake Huron wetlands were compared to assess water quality and test potential metrics for an Index of Ecological Integrity (IEI) for Great Lake coastal wetlands. Macroinvertebrates were collected using sediment coring and dip-net sampling monthly from June through September 1996. One wetland was impacted by domestic wastewater from a lagoon, urban storm-water runoff, and local marina traffic. A nearby wetland with a similar size drainage basin, no wastewater or urban storm-water input or marina traffic served as a reference. Greatest differences in chemistry between sites occurred during lagoon discharge in September. Compared to the reference, the impacted wetland had higher Cl, NH4-N, NO3-N, soluble reactive P, conductivity and lower dissolved oxygen levels. There were fewer insects, especially Ephemeroptera and Trichoptera in the impacted wetland than in the reference wetland. A greater proportion of macroinvertebrates in the impacted wetland were Amphipoda, Isopoda, and Naididae. Observed differences in macroinvertebrate communities were used to test 38 metrics, used in indices of biological integrity for streams, to determine their potential as metrics for an index of ecological integrity for Great Lake wetlands. Invertebrate attributes sensitive to water quality changes were identified as candidate metrics if they exhibited low within-site variability and detected differences between wetlands for each sampling period. Candidate metrics included relative abundance of Ephemeroptera, Isopoda, Trichoptera, predators, collector-filterers, and herbivore/detritivore ratio.

Performance of viruses and bacteriophages for fecal source determination in a multi-laboratory, comparative study.

An inter-laboratory study of the accuracy of microbial source tracking (MST) methods was conducted using challenge fecal and sewage samples that were spiked into artificial freshwater and provided as unknowns (blind test samples) to the laboratories. The results of the Source Identification Protocol Project (SIPP) are presented in a series of papers that cover 41 MST methods. This contribution details the results of the virus and bacteriophage methods targeting human fecal or sewage contamination. Human viruses used as source identifiers included adenoviruses (HAdV), enteroviruses (EV), norovirus Groups I and II (NoVI and NoVII), and polyomaviruses (HPyVs). Bacteriophages were also employed, including somatic coliphages and F-specific RNA bacteriophages (FRNAPH) as general indicators of fecal contamination. Bacteriophage methods targeting human fecal sources included genotyping of FRNAPH isolates and plaque formation on bacterial hosts Enterococcus faecium MB-55, Bacteroides HB-73 and Bacteroides GB-124. The use of small sample volumes (≤50 ml) resulted in relatively insensitive theoretical limits of detection (10-50 gene copies or plaques × 50 ml(-1)) which, coupled with low virus concentrations in samples, resulted in high false-negative rates, low sensitivity, and low negative predictive values. On the other hand, the specificity of the human virus methods was generally close to 100% and positive predictive values were ∼40-70% with the exception of NoVs, which were not detected. The bacteriophage methods were generally much less specific toward human sewage than virus methods, although FRNAPH II genotyping was relatively successful, with 18% sensitivity and 85% specificity. While the specificity of the human virus methods engenders great confidence in a positive result, better concentration methods and larger sample volumes must be utilized for greater accuracy of negative results, i.e. the prediction that a human contamination source is absent.

The cost of tolerance: sensitivity of stream benthic communities to UV-B and metals.

The ability to tolerate disturbance is a defense strategy that minimizes the effects of damage to fitness and is essential for sustainability of populations, communities, and ecosystems. Despite the apparent benefits of tolerance, there may be an associated cost that results in a deficiency of a system to respond to additional disturbances. Aquatic ecosystems are often exposed to a variety of natural and anthropogenic disturbances, and the effects of these compound perturbations are not well known. In this investigation, we examine whether tolerance to one stressor, metals, results in a cost of increased sensitivity to an additional stressor, ultraviolet-B (UV-B) radiation. Heavy metal pollution is recognized as a major environmental problem in Rocky Mountain streams. These high-elevation, typically clear streams may be at particular risk to elevated UV-B levels associated with reduced levels of ozone. Microcosm experiments were conducted using natural stream benthic communities collected from a reference site and a site with a long-term history of heavy-metal pollution. Direct and interactive effects of heavy metals and UV-B radiation on structural and functional characteristics of benthic communities were evaluated among four treatments: control, UV-B, metals, and metal and UV-B. Communities from the metal-polluted site were more tolerant of metals but less tolerant to UV-B compared to reference communities. Increased mayfly drift and reduced metabolism in response to metal exposure were observed in reference communities but not in the metal-polluted communities. In contrast to these results, UV-B radiation significantly reduced community metabolism, total macroinvertebrate abundance, and abundances of mayflies, caddisflies, and dipterans from the metal-polluted site, but had no effects on benthic communities from the reference site. ANOSIM results demonstrated that community responses differed among treatments at both sites. Metals had the largest impact on community differences at both sites, while UV-B had greater impacts at the metal-polluted site. This research demonstrates the need to account for potential costs associated with tolerance and that these costs can result in behavioral, structural, and functional impacts to benthic communities.

Effects of vertebrate hormones on development and sex determination in Daphnia magna

Daphnia (Crustacea) are extensively used as model organisms in ecotoxicology; however, little is known regarding their endocrine system. This study examines Daphnia vulnerability to vertebrate hormones. Twelve natural or synthetic vertebrate hormones were screened for activity on developmental and reproductive processes in Daphnia magna. Natural hormones tested included: beta-estradiol, gonadotropin, hydrocortisone, insulin, melatonin, progesterone, somatostatin, testosterone, and thyroxine at concentrations ranging from 1 to 100 microg/L. Synthetic hormones tested included diethylstilbestrol (estrogenic), R-1881 (androgen), and ICI-182,780 (antiestrogen); all hormones were screened with a 6-d assay. Additionally, progesterone, insulin, testosterone, and thyroxine were screened for 25 d. Diethylstilbestrol decreased D. magna growth rate while thyroxine increased it. Short-term testosterone exposure reduced D. magna fecundity; however, long-term exposure did not, potentially indicating testosterone hydroxylation with long-term exposure. Hormones commonly considered sex-hormones (estrogens and androgens) in vertebrates do not appear to control sexual differentiation in D. magna; however, several vertebrate hormones do affect reproduction and development in D. magna making D. magna a potentially useful tool in monitoring for the presence of these hormones or compounds that mimic them.

Effects of common-use pesticides on developmental and reproductive processes in Daphnia:

Daphnia magna were evaluated for use as a screen for pesticides that have been demonstrated to have estrogenic (o?p?-DDT, di-n-butyl phthalate, toxaphene), anti-androgenic (p?p-DDE, linuron), thyroid (acetochlor, alachlor, metribuzin), insulin (amitraz) or lutenizing hormone (2,4-D) activity in vertebrates, and to establish daphnid sensitivity to these compounds. Pesticides with unknown effects on vertebrate endocrine systems (chlorosulfuran, cyanazine, diflubenzuron, metolachlor, and diquat) were also evaluated. Compounds were assayed for six days at environmentally relevant concentrations ranging from 0.001 to 100 mg/L, using female Daphnia and their offspring. Sublethal endpoints included offspring sex (sex determination), clutch size (fecundity), and adult size (growth rate). Toxaphene was the only compound that affected sexual differentiation, increasing male production. Daphnia fecundity declined with exposure to toxaphene, and daphnid growth rates were reduced by acetochlor exposure. Diflubenzuron, o?p?-DDT, and p?p-DDE significantly reduced Daphnia survival. No correlation existed between affected reproductive or developmental processes and specific endocrine systems or subsystems. Results from this study indicate that Daphnia make a good screen for assessing potential environmental impacts but are not a useful indicator of pesticide hormonal activity in vertebrates. This assay consistently detected sublethal but ecologically relevant effects of these pesticides on Daphnia at environmentally relevant concentrations typically below their listed EC50 value.

Invading the invaders: reproductive and other mechanisms mediating the displacement of zebra mussels by quagga mussels

Dreissenids are invasive bivalves, native to water bodies of the Ponto-Caspian region of southwestern Asia. Following dispersion in Europe in the early nineteenth century, they were accidentally introduced into the Great Lakes region of North America in the 1980s and 1990s. Recently, they were discovered in the southwestern USA. Initially, Dreissena polymorpha (zebra mussel, ZM) spread more rapidly than Dreissena rostriformis bugensis (quagga mussel, QM); however, QM is becoming predominant in many areas of the Great Lakes and was the first to appear west of the Continental Divide, in Lake Mead. In Europe, as well, ZM was the first species to spread widely in western Europe from its endemic range; however, QM have recently been found in areas previously colonized only by ZM. This article reviews the dynamics of this double dreissenid invasion and considers the question: what mechanisms mediate the displacement of ZM by QM? Despite their similar appearance, QM differ from ZM in temperature and salinity tolerance, byssal thread attachment, growth, respiration rates, assimilation efficiency, enzymes such as thiaminase, depth of occurrence, and reproduction. Differences in reproduction include the depth at which reproductively active animals are found, the temperature at which spawning can be initiated, number of gametes produced, and length and timing of their annual reproductive cycle. A hypothetical role of hybrids between the species mediating species change is suggested. Future investigations of the displacement of ZM by QM should consider the role of reproductive differences (hybrids, responses to environmental chemicals, etc.) in mediating the change.

Optical bioassay for measuring sublethal toxicity of insecticides in Daphnia pulex

Many emerging contaminants tend to be biologically active at very low concentrations, occur in water as part of complex mixtures, and impact biota in ways that are not detected using traditional toxicity tests (e.g., median lethal concentration). To evaluate emerging contaminants, the authors developed a method for detecting sublethal behavioral effects by quantifying the swimming behavior of Daphnia pulex, a model organism for studying aquatic toxicity. This optical tracking technique is capable of measuring many swimming parameters, 2 of which-cumulative distance and angular change-are presented. To validate this technique, 2 prototypical compounds that exhibit different modes of action as well as corresponding insecticides that are commonly found in surface waters were investigated. The acetylcholinesterase (AChE) inhibitor physostigmine was used as the prototypical compound for the large number of AChE inhibitor insecticides (e.g., chlorpyrifos). Nicotine was used as the prototypical compound for neonicotinoid insecticides (e.g., imidacloprid). Results demonstrate that this assay is capable of detecting sublethal behavioral effects that are concentration-dependent and that insecticides with the same mode of action yield similar results. The method can easily be scaled up to serve as a high-throughput screening tool to detect sublethal toxic effects of a variety of chemicals. This method is likely to aid in enhancing the current understanding of emerging contaminants and to serve as a novel water-quality screening tool.

Quantifying uncertainty in the trophic magnification factor related to spatial movements of organisms in a food web

Trophic magnification factors (TMFs) provide a method of assessing chemical biomagnification in food webs and are increasingly being used by policy makers to screen emerging chemicals. Recent reviews have encouraged the use of bioaccumulation models as screening tools for assessing TMFs for emerging chemicals of concern. The present study used a food web bioaccumulation model to estimate TMFs for polychlorinated biphenyls (PCBs) in a riverine system. The uncertainty associated with model predicted TMFs was evaluated against realistic ranges for model inputs (water and sediment PCB contamination) and variation in environmental, physiological, and ecological parameters included within the model. Finally, the model was used to explore interactions between spatial heterogeneity in water and sediment contaminant concentrations and theoretical movement profiles of different fish species included in the model. The model predictions of magnitude of TMFs conformed to empirical studies. There were differences in the relationship between the TMF and the octanol-water partitioning coefficient (KOW ) depending on the modeling approach used; a parabolic relationship was predicted under deterministic scenarios, whereas a linear TMF-KOW relationship was predicted when the model was run stochastically. Incorporating spatial movements by fish had a major influence on the magnitude and variation of TMFs. Under conditions where organisms are collected exclusively from clean locations in highly heterogeneous systems, the results showed bias toward higher TMF estimates, for example the TMF for PCB 153 increased from 2.7 to 5.6 when fish movement was included. Small underestimations of TMFs were found where organisms were exclusively sampled in contaminated regions, although the model was found to be more robust to this sampling condition than the former for this system.

Identification of the critical timing of sex determination in Daphnia magna (Crustacea, Branchiopoda) for use in toxicological studies

Daphnia are often used as test organisms to determine toxicity of chemicals found in the environment. Fecundity and mortality are the classic endpoints in such tests; however, there is increased interest in other sub-lethal endpoints. Most Daphnia reproduce by cyclic parthenogenesis, typically reproducing asexually to produce genetically identical females. Environmental cues trigger the production of males allowing for sexual reproduction. This ability to switch reproductive strategies has been increasingly used as a bioassay endpoint in screens for sub-lethal effects of contaminants. In order to optimize such test, it is necessary to know when sex is determined during Daphnia development. A previous study using the insect juvenile hormone methyl farnesoate has shown that sex determination occurred during the egg maturation period in Daphnia. Our study exposed female Daphnia magna carrying eggs and embryos at different stages of maturation, to the insecticide toxaphene to determine if the timing of sex determination is similarly influenced by a pesticide. Our results suggest that in response to toxaphene exposure sex is determined in the immature oocyte, before the final maturation cleavage, and before the developing egg is extruded into the brood chamber. Thus, sex determination is transgenerational, being determined while the egg is still immature and in the mother’s ovary.

A kinetic study of accumulation and elimination of microcystin-LR in yellow perch (Perca flavescens) tissue and implications for human fish consumption.

Fish consumption is a potential route of human exposure to the hepatotoxic microcystins, especially in lakes and reservoirs that routinely experience significant toxic Microcystis blooms. Understanding the rates of uptake and elimination for microcystins as well as the transfer efficiency into tissues of consumers are important for determining the potential for microcystins to be transferred up the food web and for predicting potential human health impacts. The main objective of this work was to conduct laboratory experiments to investigate the kinetics of toxin accumulation in fish tissue. An oral route of exposure was employed in this study, in which juvenile yellow perch (Perca flavescens) were given a single oral dose of 5 or 20 μg of microcystin-LR (MC-LR) via food and accumulation in the muscle, liver, and tank water were measured over 24 h. Peak concentrations of the water soluble fraction of microcystin were generally observed 8–10 h after dosing in the liver and after 12–16 h in the muscle, with a rapid decline in both tissues by 24 h. Up to 99% of the total recoverable (i.e., unbound) microcystin was measured in the tank water by 16 h after exposure. The relatively rapid uptake and elimination of the unbound fraction of microcystin in the liver and muscle of juvenile yellow perch within 24 h of exposure indicates that fish consumption may not be a major route of human exposure to microcystin, particularly in the Great Lakes.