Peter R. Lazaro

Acute and chronic toxicity of technical-grade pesticides to glochidia and juveniles of freshwater mussels (unionidae)

Chemical contaminants are among many potential factors involved in the decline of freshwater mussel populations in North America, and the effects of pesticides on early life stages of unionid mussels are largely unknown. The objective of this study was to determine the toxicity of technical-grade current-use pesticides to glochidia and juvenile life stages of freshwater mussels. We performed acute toxicity tests with glochidia (five species) and juveniles (two species) exposed to a suite of current-use pesticides including herbicides (atrazine and pendimethalin), insecticides (fipronil and permethrin), and a reference toxicant (NaCl). Because of limited availability of test organisms, not all species were tested with all pesticides. Toxicity tests with fungicides (chlorothalonil, propiconazole, and pyraclostrobin) were performed with one species (Lampsilis siliquoidea). Lampsilis siliquoidea glochidia and juveniles were highly sensitive to the fungicides tested but the technical-grade herbicides and insecticides, at concentrations approaching water solubility, were not acutely toxic to this or the other unionid species. In a 21-d chronic test with four-month-old juvenile L. siliquoidea, the 21-d median effective concentration (EC50) with atrazine was 4.3 mg/L and in atrazine treatments >or=3.8 mg/L mussel growth was significantly less than controls. The relatively high sensitivity of L. siliquoidea to chlorothalonil, propiconazole, and pyraclostrobin is similar to that reported for other aquatic organisms commonly used for toxicity testing. The relative risk associated with acute exposure of early life stages of mussels to technical-grade atrazine, pendimethalin, fipronil, and permethrin is likely low; however, survival and growth results with juvenile L. siliquoidea indicate that chronic exposure to high concentrations (>/=3.8 mg/L) of atrazine may have the potential to impact mussel populations and warrants further investigation.

Acute and chronic toxicity of pesticide formulations (atrazine, chlorpyrifos, and permethrin) to glochidia and juveniles of Lampsilis siliquoidea

Freshwater mussels are among the most imperiled faunal groups in North America; approximately 67% of the nearly 300 native freshwater mussel species (family Unionidae) are listed as endangered, threatened, or of special concern. Despite evidence that glochidia and juvenile life stages are highly sensitive to some chemical contaminants, the effects of pesticides on early life stages of unionid mussels are largely unknown. In the United States, pesticide registration is based on toxicity data of the active ingredient, not formulations as they are sold and applied. Some pesticide formulations, however, are more toxic than their active ingredient (technical-grade pesticide) alone because of the presence of surfactants, adjuvants, or other ingredients in the formulation. The objective of the present study was to compare the toxicity of active ingredients of several current-use pesticides (atrazine, chlorpyrifos, and permethrin) to the toxicity of pesticide formulations to glochidia and juvenile life stages of a freshwater mussel (Lampsilis siliquoidea). The atrazine formulation (Aatrex) was more toxic than technical-grade atrazine in chronic tests with juvenile L. siliquoidea. For other pesticides, acute and chronic toxicity of technical-grade pesticides were similar to the toxicity of pesticide formulations. Median effective concentrations for chlorpyrifos were 0.43 mg/L for glochidia at 48 h, 0.25 mg/L for juveniles at 96 h, and 0.06 mg/L for juveniles at 21 d. Atrazine and permethrin as well as their formulations did not cause significant acute toxicity in glochidia or juveniles at exposure concentrations approaching water-solubility limits. Additional research is needed on other pesticides with different modes of action, on the role of different routes of exposure, and with other species of unionid mussels to evaluate similarities of toxic response.

Influence of water quality and associated contaminants on survival and growth of the endangered Cape Fear shiner (Notropis mekistocholas)

The Cape Fear shiner (Notropis mekistocholas) is a recently described cyprinid species endemic to the Cape Fear River Basin of North Carolina, USA. Only five populations of the fish remain; thus, it is listed as endangered by the U.S. Government. Determining habitat requirements of the Cape Fear shiner, including water quality and physical habitat, is critical to the survival and future restoration of the species. To assess water quality in the best remaining and in the historical habitats, we conducted a 28-d in situ bioassay with captively propagated Cape Fear shiners. Fish were deployed at 10 sites in three rivers, with three cages per site and 20 fish per cage. Water and sediment samples were collected and analyzed for selected metals and organic contaminants. Passive sampling devices also were deployed at each site and analyzed for organic contaminants at test termination. Fish survival, growth (as measured by an increase in total length), and contaminant accumulation were measured on completion of the bioassay. Survival of caged fish averaged 76% (range, 53-100%) and varied significantly among sites and rivers. Caged fish accumulated quantities of cadmium, mercury, polychlorinated biphenyls, and other persistent contaminants over the test duration and grew significantly at only four sites. No apparent relations were observed between exposure to or accumulation of a specific contaminant and reduced growth or survival of fish among all the sites. However, a generalized hazard assessment showed that certain sites exhibited trends in cumulative contaminant presence with reduced fish survival and growth, thereby enabling the identification of the existing riverine habitat most suitable for reintroduction or population augmentation of this endangered fish.

Contaminants in tropical island streams and their biota

ABSTRACT Environmental contamination is problematic for tropical islands due to their typically dense human populations and competing land and water uses. The Caribbean island of Puerto Rico (USA) has a long history of anthropogenic chemical use, and its human population density is among the highest globally, providing a model environment to study contaminant impacts on tropical island stream ecosystems. Polycyclic Aromatic Hydrocarbons, historic‐use chlorinated pesticides, current‐use pesticides, Polychlorinated Biphenyls (PCBs), and metals (mercury, cadmium, copper, lead, nickel, zinc, and selenium) were quantified in the habitat and biota of Puerto Rico streams and assessed in relation to land‐use patterns and toxicological thresholds. Water, sediment, and native fish and shrimp species were sampled in 13 rivers spanning broad watershed land‐use characteristics during 2009–2010. Contrary to expectations, freshwater stream ecosystems in Puerto Rico were not severely polluted, likely due to frequent flushing flows and reduced deposition associated with recurring flood events. Notable exceptions of contamination were nickel in sediment within three agricultural watersheds (range 123–336 ppm dry weight) and organic contaminants (PCBs, organochlorine pesticides) and mercury in urban landscapes. At an urban site, PCBs in several fish species (Mountain Mullet Agonostomus monticola [range 0.019–0.030 ppm wet weight] and American Eel Anguilla rostrata [0.019–0.031 ppm wet weight]) may pose human health hazards, with concentrations exceeding the U.S. Environmental Protection Agency (EPA) consumption limit for 1 meal/month. American Eel at the urban site also contained dieldrin (range < detection‐0.024 ppm wet weight) that exceeded the EPA maximum allowable consumption limit. The Bigmouth Sleeper Gobiomorous dormitor, an important piscivorus sport fish, accumulated low levels of organic contaminants in edible muscle tissue (due to its low lipid content) and may be most suitable for human consumption island‐wide; only mercury at one site (an urban location) exceeded EPAs consumption limit of 3 meals/month for this species. These results comprise the first comprehensive island‐wide contaminant assessment of Puerto Rico streams and biota and provide natural resource and public health agencies here and in similar tropical islands elsewhere with information needed to guide ecosystem and fisheries conservation and management and human health risk assessment. HIGHLIGHTSPuerto Rico is a model environment to study contaminants in tropical island streams.Water, sediment, and native fish and shrimp species were sampled in 13 rivers.Stream habitat and biota were not severely polluted due to frequent flushing flows and floods.Results may inform human health and development of fish consumption guidelines for Puerto Rico.