DEVELOPING TOXICOLOGICAL TESTING AND FECUNDITY ASSESSMENT METHODS USING ESTUARINE FISH TO MONITOR LEGACY CONTAMINATION

Abstract

Estuarine sediments bear the legacy of urban and industrial pollution, where benthic organisms and their predators are exposed to persistent organic pollutants (POPs) such as Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs), and Dioxins. We are using the mummichog (Fundulus heteroclitus) to study fish health in historically contaminated urban tidal rivers. This thesis contains four chapters: an introductory literature review, studies developing embryo-larval sediment contact assays for mummichog and sheepshead minnow (Cyprinodon variegatus), methods for assessing fecundity in female mummichog sourced from a historically contaminated urban river, and general conclusions. The introduction provides background to sediment contamination and discusses the rationale for the use of mummichog as a species of interest for toxicological assessment. It also proposes the use of sheepshead minnow as a surrogate to assess sediment toxicity and facilitate comparison with existing literature. The second chapter describes in detail a lab methodology for an embryo-larval whole sediment toxicity assay with mummichog and sheepshead minnow and discusses the results of tests with each species to spiked sediment exposures. The proposed approach modifies an established water column toxicity test, exposing fish embryos to three POP contaminants in spiked sediment dilution series. The contaminants used in the sediment spiking belong to more general classes of POPs: PAHs, PCBs, and Dioxins, and are commonly found in degraded aquatic habitats. The specific contaminants used in the exposures are Creosote, Aroclor 1254, and 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), and their impact is assessed using mortality, health condition, growth, and time to hatch. The results indicate that both species are amenable to toxicity testing with whole sediment exposure, with different species sensitivity as reflected in variable endpoint responses. The third chapter explores fecundity methods as a proxy of environmental effects on mummichog to expand biomonitoring beyond histopathology. This effort applies gonadosomatic index (GSI) and oocyte enumeration methods, throughout the reproductive season to mummichog collected from four spatially distinct populations in an urbanized tidal river. Overall, this work aims to further establish mummichog as a site-relevant species for toxicity testing, both in the lab and biomonitoring.