Soil bioretention protects juvenile salmon and their prey from the toxic impacts of urban stormwater runoff.

Green stormwater infrastructure (GSI), or low impact development, encompasses a diverse and expanding portfolio of strategies to reduce the impacts of stormwater runoff on natural systems. Benchmarks for GSI success are usually framed in terms of hydrology and water chemistry, with reduced flow and loadings of toxic chemical contaminants as primary metrics. Despite the central goal of protecting aquatic species abundance and diversity, the effectiveness of GSI treatments in maintaining diverse assemblages of sensitive aquatic taxa has not been widely evaluated. In the present study we characterized the baseline toxicity of untreated urban runoff from a highway in Seattle, WA, across six storm events. For all storms, first flush runoff was toxic to the daphniid Ceriodaphnia dubia, causing up to 100% mortality or impairing reproduction among survivors. We then evaluated whether soil media used in bioretention, a conventional GSI method, could reduce or eliminate toxicity to juvenile coho salmon (Oncorhynchus kisutch) as well as their macroinvertebrate prey, including cultured C. dubia and wild-collected mayfly nymphs (Baetis spp.). Untreated highway runoff was generally lethal to salmon and invertebrates, and this acute mortality was eliminated when the runoff was filtered through soil media in bioretention columns. Soil treatment also protected against sublethal reproductive toxicity in C. dubia. Thus, a relatively inexpensive GSI technology can be highly effective at reversing the acutely lethal and sublethal effects of urban runoff on multiple aquatic species.

Zebrafish and clean water technology: assessing soil bioretention as a protective treatment for toxic urban runoff.

Urban stormwater contains a complex mixture of contaminants that can be acutely toxic to aquatic biota. Green stormwater infrastructure (GSI) is a set of evolving technologies intended to reduce impacts on natural systems by slowing and filtering runoff. The extent to which GSI methods work as intended is usually assessed in terms of water quantity (hydrology) and quality (chemistry). Biological indicators of GSI effectiveness have received less attention, despite an overarching goal of protecting the health of aquatic species. Here we use the zebrafish (Danio rerio) experimental model to evaluate bioinfiltration as a relatively inexpensive technology for treating runoff from an urban highway with dense motor vehicle traffic. Zebrafish embryos exposed to untreated runoff (48-96h; six storm events) displayed an array of developmental abnormalities, including delayed hatching, reduced growth, pericardial edema, microphthalmia (small eyes), and reduced swim bladder inflation. Three of the six storms were acutely lethal, and sublethal toxicity was evident across all storms, even when stormwater was diluted by as much as 95% in clean water. As anticipated from exposure to cardiotoxic polycyclic aromatic hydrocarbons (PAHs), untreated runoff also caused heart failure, as indicated by circulatory stasis, pericardial edema, and looping defects. Bioretention treatment dramatically improved stormwater quality and reversed nearly all forms of developmental toxicity. The zebrafish model therefore provides a versatile experimental platform for rapidly assessing GSI effectiveness.

Molecular epizootiology of genotoxic events in marine fish: linking contaminant exposure, DNA damage, and tissue-level alterations.

Molecular epizootiological studies are increasingly being used to investigate environmental effects of genotoxic contaminants. The assessment of damage to DNA and linking the damage to subsequent molecular, cellular, or tissue-level alterations is a central component of such studies. Our research has focused on the refinement of the 32P-postlabeling assay for measuring covalent DNA-xenobiotic adducts arising from exposure to polycyclic aromatic compounds, using DNA adducts as molecular dosimeters of genotoxic contaminant exposure in biomonitoring studies, and investigating the relationship of DNA adduct formation to toxicopathic liver disease, including neoplastic lesions. A combination of field and laboratory studies using the 32P-postlabeling assay has shown that DNA adducts in marine fish are effective molecular dosimeters of genotoxic contaminant exposure. Investigations of the relationship of DNA adduct formation to neoplastic liver disease have shown that elevated levels of DNA adducts in certain fish species from contaminated coastal sites are associated with increased prevalences of toxicopathic hepatic lesions, including neoplasms, and that the ability to assess DNA damage has helped to explain, in part, species differences in lesion prevalence. Moreover, in a study of a site in Puget Sound contaminated with polycyclic aromatic compounds, we have shown, for the first time, that elevated levels of hepatic DNA adducts are a significant risk factor for certain degenerative and preneoplastic lesions occurring early in the histogenesis of hepatic neoplasms in feral English sole (Pleuronectes vetulus). These latter findings coupled with our current studies of mutational events in the K-ras proto-oncogene should provide further mechanistic substantiation that mutagenic events resulting from exposure to complex mixtures of genotoxic polycyclic aromatic compounds are involved in the etiology of hepatic neoplasia in English sole.

Concentration and dispersal of a Pseudo-nitzschia bloom in Penn Cove, Washington, USA.

A bloom of the pennate diatom Pseudo-nitzschia, several species of which are associated with the production of the potent excitotoxin domoic acid, was observed in a Puget Sound, Washington embayment in July and August of 1997. Penn Cove, which receives nutrients from the nearby Skagit River and abundant sunshine during summer months due to its location in the rain shadow of the Olympic Mountains, is the home of a commercial mussel farm which supplies shellfish to many coastal areas of the USA. Levels of domoic acid in mussels increased to 3 ppm on 6 and 10 July, corresponding to the observation of a brown algal bloom in Penn Cove. Four species of Pseudo-nitzschia (P. pungens, P. multiseries, P. australis, and P. pseudodelicatissima) were present in our samples from the cove, corresponding to levels of domoic acid in seawater ranging from 0.1-0.8 mirog l(-1) as measured by a receptor binding assay. The highest Pseudo-nitzschia concentration during the time of our sampling was 13 million cells per liter on 28 July. The bloom of Pseudo-nitzschia occurred after a period of strong discharge from the Skagit River and rain accompanied by elevated south and southeasterly winds. Stratification of the cove, providing optimal bloom conditions, was facilitated by weak winds, sunshine, and a freshwater lens at the mouth of the cove. The position of the Pseudo-nitzschia bloom was influenced by buoyancy fronts caused by exchange of water within the cove with that of Saratoga Passage. The decay of this bloom in Penn Cove was accompanied by decreasing nitrate levels at all measured depths. These and future observations aid in the development of a model for prediction of toxic bloom events in the shallow embayments of Puget Sound.

Stability of cytochrome P4501A-associated enzyme activity in cryogenically stored teleost liver samples.

Induction of cytochrome P4501A (CYP1A), more specifically the associated enzyme activity aryl hydrocarbon hydroxylase (AHH), has been shown to be one of the most sensitive measures of exposure of vertebrate animals to a range of organic chemical contaminants. However, in order to reliably use this biochemical method for analyzing archived samples, the stability of the enzyme activity in storage must be ascertained. Stability of AHH activity was determined for both tissue sections and subcellular fractions of liver collected from English sole (Pleuronectes vetulus), and held in cryogenic storage for up to 24 months. Our overall recommendations for sample collection, handling, storage, and assay are given.