Unraveling associations between cyanobacteria blooms and in-lake environmental conditions in Missisquoi Bay, Lake Champlain, USA, using a modified self-organizing map.

Exploratory data analysis on physical, chemical, and biological data from sediments and water in Lake Champlain reveals a strong relationship between cyanobacteria, sediment anoxia, and the ratio of dissolved nitrogen to soluble reactive phosphorus. Physical, chemical, and biological parameters of lake sediment and water were measured between 2007 and 2009. Cluster analysis using a self-organizing artificial neural network, expert opinion, and discriminant analysis separated the data set into no-bloom and bloom groups. Clustering was based on similarities in water and sediment chemistry and non-cyanobacteria phytoplankton abundance. Our analysis focused on the contribution of individual parameters to discriminate between no-bloom and bloom groupings. Application to a second, more spatially diverse data set, revealed similar no-bloom and bloom discrimination, yet a few samples possess all the physicochemical characteristics of a bloom without the high cyanobacteria cell counts, suggesting that while specific environmental conditions can support a bloom, another environmental trigger may be required to initiate the bloom. Results highlight the conditions coincident with cyanobacteria blooms in Missisquoi Bay of Lake Champlain and indicate additional data are needed to identify possible ecological contributors to bloom initiation.

Investigating public preferences for managing Lake Champlain using a choice experiment.

The Lake Champlain Basin in Vermont and New York, USA and Quebec, Canada includes a large lake and watershed with complex management issues. A transboundary comprehensive management plan prepared for the lake includes 11 goals across many issue areas. We developed a choice experiment to examine public preferences for alternative Lake Champlain management scenarios across these issue areas. Five ecosystem attributes (water clarity-algae blooms, public beach closures, land use change, fish consumption advisories and the spread of water chestnut, an invasive plant) were varied across three levels and arrayed into paired comparisons following an orthogonal fractional factorial design. Two thousand questionnaires were distributed to basin residents, each including nine paired comparisons that required trading off two, three or four attributes. Completed surveys yielded 6541 responses which were analyzed using binary logistic regression. The results showed that although water clarity and beach closures were important, safe fish consumption was the strongest predictor of choice. Land use pattern and water chestnut distribution were weaker but also significant predictors, with respondents preferring less land development and preservation of the agricultural landscape. Current management efforts in the Lake Champlain Basin are heavily weighted toward improving water clarity by reducing phosphorus pollution. Our results suggest that safe fish consumption warrants additional management attention. Because choice experiments provide information that is much richer than the simple categorical judgments more commonly used in surveys, they can provide managers with information about tradeoffs that could be used to enhance public support and maximize the social benefits of an ecosystem management program.

Elevated concentrations of ethinylestradiol, 17beta-estradiol, and medroxyprogesterone have little effect on reproduction and survival of Ceriodaphnia dubia.

Wastewater effluent contains synthetic and natural hormones, often in complex mixtures, that may be associated with reproductive abnormalities in fish and other aquatic biota. We exposed the sentinel invertebrate Ceriodaphnia dubia to the natural estrogen 17beta-estradiol (E(2)), a synthetic estrogen, ethinylestradiol (EE(2)), and a synthetic progestin, medroxyprogesterone in a 7-day test. These compounds had no significant effect on reproduction or survival even at 10(6) times the concentrations at which reproductive effects have been documented in several fish species. C. dubia is routinely used for screening the toxicity of wastewater effluent. However, in the standard chronic 7-day exposure the endpoints of survival and reproduction were insensitive to several synthetic and natural vertebrate hormones. The C. dubia 7-day chronic toxicity test is probably not a useful monitoring tool for vertebrate hormones and their pharmaceutical analogs unless other sensitive endpoints such as maturation rates, molt frequency, and offspring sex ratios are incorporated in a practical manner.

The effects of environmentally relevant mixtures of estrogens on Japanese medaka (Oryzias latipes) reproduction.

Wastewater effluent contains a variety of estrogenic compounds that vary in potency, but each of which contributes to the overall estrogenicity of the effluent. We hypothesized that the effects of mixtures of estrogens on reproduction in pair breeding medaka (Oryzias latipes) could be predicted by their relative estrogenicity. Relative estrogenicity was defined by the ability of estrogenic compounds to induce vitellogenesis in various species of male fish. We exposed reproducing pairs of medaka to mixtures of the environmental estrogens nonylphenol (NP), 17alpha-ethinylestradiol (EE(2)), and natural 17beta-estradiol (E(2)), as well as treatments of equivalent estrogenicity that were composed of E(2) alone. Reproducing medaka exposed to mixtures of estrogenic compounds and equipotent treatments of estradiol alone had very similar responses in mortality and reproduction (fecundity, number of spawns). However, mixtures of NP, E(2), and EE(2) elicited lower vitellogenic induction than equipotent concentrations of E(2) alone. Therefore, relative estrogenicity was a good model for predicting some, but not all, reproductive responses, and simple additive mixture models may not predict all relevant physiological responses.

Defining acceptable levels for ecological indicators: an approach for considering social values.

Ecological indicators can facilitate an adaptive management approach, but only if acceptable levels for those indicators have been defined so that the data collected can be interpreted. Because acceptable levels are an expression of the desired state of the ecosystem, the process of establishing acceptable levels should incorporate not just ecological understanding but also societal values. The goal of this research was to explore an approach for defining acceptable levels of ecological indicators that explicitly considers social perspectives and values. We used a set of eight indicators that were related to issues of concern in the Lake Champlain Basin. Our approach was based on normative theory. Using a stakeholder survey, we measured respondent normative evaluations of varying levels of our indicators. Aggregated social norm curves were used to determine the level at which indicator values shifted from acceptable to unacceptable conditions. For seven of the eight indicators, clear preferences were interpretable from these norm curves. For example, closures of public beaches because of bacterial contamination and days of intense algae bloom went from acceptable to unacceptable at 7-10 days in a summer season. Survey respondents also indicated that the number of fish caught from Lake Champlain that could be safely consumed each month was unacceptably low and the number of streams draining into the lake that were impaired by storm water was unacceptably high. If indicators that translate ecological conditions into social consequences are carefully selected, we believe the normative approach has considerable merit for defining acceptable levels of valued ecological system components.

Application of the WHO alert level framework to cyanobacterial monitoring of Lake Champlain, Vermont.

The increasing incidence of toxic cyanobacteria blooms worldwide has created a need for practical and efficient monitoring in order to protect public health. We developed a monitoring and alert framework based on World Health Organization (WHO) recommendations and applied it on Lake Champlain during the summers of 2002-2004. The protocol began with collection of net samples of phytoplankton in order to maximize the chance of finding potential toxin-producing cyanobacteria. Samples were collected lake-wide in partnership with ongoing monitoring efforts, but because open water sample sites did not capture conditions along the shoreline, we added near-shore and shoreline stations in problem areas. Samples were examined qualitatively until potential toxin-producing taxa were found. Then quantitative analyses began, using a rapid screening method to estimate cell density based on colony size. A final cell density of 4000 cells/mL triggered toxin analyses. Primary analysis was for microcystins using ELISA methods. Cell densities, locations of colonies, and toxin concentrations were reported weekly to public health officials. We found that screening for potential toxin-producing cyanobacteria and then measuring toxin concentrations when cell densities reached critical levels worked well to identify problem locations. Although the WHO recommends using chlorophyll a concentration, it was not a good indicator of problem densities of potential toxin-producing cyanobacteria. Our cell density screening method missed no developing blooms but produced less precise density estimates at high cell counts. Overall, our framework appears to provide an efficient and effective method for monitoring cyanotoxin risks.

Effects of metal and organophosphate mixtures on Ceriodaphnia dubia survival and reproduction.

The toxicity of mixtures of copper, zinc, and diazinon were determined for Ceriodaphnia dubia using 7-d survival and reproduction tests. Fifteen treatments, including combinations of the chemicals at 0, 25, 50, 75, and 100% of their individual median lethal concentrations, adding up to one toxic unit (TU) were tested. The TU was then used to classify each mixture response as additive, greater than additive, or less than additive. For survival, additive responses occurred in the 75% zinc plus 25% diazinon and the 50% copper plus 25% zinc plus 25% diazinon treatments. For reproduction, additive responses occurred in the 75% copper plus 25% zinc, 75% copper plus 25% diazinon, and 75% zinc plus 25% diazinon treatments. Copper and zinc played a greater role in toxicity than diazinon did. Less-than-additive interactions were found in all remaining mixtures, perhaps because of differences in mode of action between diazinon and metals. Consideration of dose-response curves can help to explain inconsistencies regarding toxic response in treatments with different ratios of the same chemicals. As TU percentages changed, mixture components were taken from different locations on differently shaped dose-response curves. Because most responses were less than additive, however, water-quality criteria based on individual concentrations probably are protective for most metal-organophosphate mixtures.

Understanding stream geomorphic state in relation to ecological integrity: evidence using habitat assessments and macroinvertebrates.

Scientists have long assumed that the physical structure and condition of stream and river channels have pervasive effects on biological communities and processes, but specific tests are few. To investigate the influence of the stream-reach geomorphic state on in-stream habitat and aquatic macroinvertebrate communities, we compared measures of habitat conditions and macroinvertebrate community composition between stable and unstable stream reaches in a paired-study design. We also explored potential associations between these ecological measures and individual geomorphic characteristics and channel adjustment processes (degradation, aggradation, overwidening, and change in planform). We found that habitat quality and heterogeneity were closely tied to stream stability, with geomorphically stable reaches supporting better habitat than unstable reaches. Geomorphic and habitat assessment scores were highly correlated (r = 0.624, P < 0.006, n = 18). Stable reaches did not support significantly greater macroinvertebrate densities than unstable reaches (t = -0.415, P > 0.689, df = 8). However, the percent of the macroinvertebrate community in the Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa was significantly correlated with the overall habitat assessment scores as well as with individual measures of geomorphic condition and habitat quality. While there is a clear need for more work in classifying and quantifying the responses of aquatic and aquatic-dependent biota to various geomorphic states and processes, this study provides solid preliminary evidence that macroinvertebrate communities are affected by the geomorphic condition of the stream reaches they inhabit and that geomorphic assessment approaches can be used as a tool for evaluating ecological integrity.

INTERACTIONS AMONG TEMPORARY AND PERMANENT MEIOFAUNA: OBSERVATIONS ON THE FEEDING AND BEHAVIOR OF SELECTED TAXA.

Meiofauna diets and behavioral patterns are relatively unknown despite the fact that in any system, predatory relationships and behavioral responses may play an important role in determining community structure. Therefore, observations on food preferences, feeding behavior, and encounter interactions of members of a meiofauna assemblage were made in the laboratory in dishes of natural sediment. The diets and behavior of two turbellarian species, Neochildia fusca and Archiloa wilsoni were examined in detail. Both are predators and both feed on a variety of other taxa, including the temporary meiofauna. Based upon the results of these experiments, a potential food web was constructed among the temporary and permanent meiofauna. The behavioral responses of these turbellarians and other members of the meiofaunal assemblage at times of encounter were also observed, categorized, and quantified. Implications of these behaviors are discussed.

The effects of meiofauna on settling macrofauna: meiofauna may structure macrofaunal communities.

When macrofaunal larvae and juveniles recruit into the benthos, they are in the same size catagory as the meiofauna. These small size classes have been consistently ignored in macrofaunal studies despite the increasingly accepted idea that communities are structured not only by interactions between adults, but also by interactions which occurred when the animals were young and in the meiofaunal size catagory. I have tested the effects of turbellarians and other meiofauna on settling macrofaunal larvae and young juveniles in a one-week field experiment. Increased densities of both turbellarians and other meiofauna (tested separately) significantly reduced densities of juvenile spionids and deposit feeders. Syllid abundances increased in high density turbellarian treatments. Nereid polychaete, other predatory polychaete, and bivalve densities showed no significant differences among treatments. By both altering densities and acting selectively on various groups of macrofaunal juveniles, meiofauna may significantly affect the structure of macrofaunal communities.