Toxicological evaluation of urban-related contaminants in estuarine ecosystems: 1. Effects of contaminants on the development and reproduction of the estuarine copepod Amphiascus tenuiremis; and 2. the role of sediment constituents on pesticide bioavaila

Human population growth compounded with sub-urban sprawl along the Southeastern US seaboard is placing an enormous pressure on coastal ecosystems. A major environmental issue associated with sub-urban sprawl and coastal development is urban storm water runoff, carrying contaminants such as polycyclic aromatic hydrocarbons (PAH's), fertilizers, pathogens, and pesticide mixtures to adjacent coastal and estuarine environments. Accordingly, this research developed a comprehensive evaluation of several issues related to coastal urban development. This study was divided into two broad themes: (1) the assessment of potential toxicological effects of field-contaminated sediments and urban-use pesticides to the estuarine meiobethic copepod Amphiascus tenuiremis (Chapters I, II and III); and (2) the evaluation of the role of various estuarine-sediment constituents on organic contaminant bioavailability and toxicity to the bivalve Mercenaria mercenaria (Chapters III, IV and V). The broader relevance of this research is to emphasize the importance of combining different approaches in the evaluation of issues related to coastal urban development. Sediments influenced by urbanization showed significant effects on copepod development and reproduction (Chapter I). However, these results were not entirely explained by high PAH concentrations. Therefore, evaluation of specific contaminants often detected at low levels in coastal areas (i.e., atrazine) provided relevant information regarding the links between copepod developmental, reproductive and population level effects and pesticide concentration (Chapter II). Furthermore, the presence of estuarine DOM pore-water was found to reduce acute and chronic pesticide toxicity of chlorothalonil and chlorpyrifos while apparently enhancing toxicity of fipronil to male A. tenuiremis copepods (Chapter II). Since estuarine sediments contain a series of particulate and dissolved constituents that could potentially influence pesticide bioavailability and toxicity to estuarine fauna, studies were design to elucidate their role on chlorpyrifos bioavailability to M. mercenaria (Chapter IV and V). These experiments showed the importance of particulate and dissolved-bound pesticide sources and the role of labile and more complex estuarine material on pesticide bioavailability (Chapter IV). Such bioavailability depends in part on the specific chemical properties of the exposure media, which facilitates or reduces pesticide binding and further bioconcentration (Chapter V).