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Center for Health and the Environment

Aquatic Toxicology

Impact of Disease on Pacific Herring Population Recovery in Prince William Sound, Alaska (Gary Marty).

The major goals of this project are 1) to determine prevalence and severity of disease in a free ranging Pacific herring population; and 2) determine how disease might be limiting population recovery after severe decline in 1993. This project has recently been expanded to determine, through modifications of an age-structured assessment model, the contribution of disease in explaining Pacific herring population fluctuations. This project builds upon work by the Aquatic Toxicology Program that began in Prince William Sound with damage assessment studies after the 1989 Exxon Valdez oil spill. As our understanding of disease in the population increases, we are better able to predict combinations of life history stages and environmental conditions that would make a population more susceptible to toxicant exposure. This work has broad application and is playing a major role in achieving better understanding of ecotoxicology and the role that environmentally persistent compounds have in producing toxicity. This research is funded jointly by Exxon Valdez Oil Spill Trustee Council (1994-2003) and the National Science Foundation (1999-2002).

Pacific Estuarine Ecosystem Indicators Research (S. Anderson and R. Higashi).

The overall goals of the PEEIR Consortium of over 40 investigators are to develop indicators that environmental managers can use of: 1) wetland ecosystem integrity and to develop an approach for synthesizing indicators into technically-defensible assessments of wetland health; 2) biotic integrity for fish and invertebrate populations within wetland communities; and 3) toxicant-induced stress and bioavailability for wetland biota. The focus of PEEIR as a whole is on wetlands because they are a) delimited, b) ecologically and commercially important and c) being lost to agricultural, urban and industrial development. Dr. Higashi is coordinator for the Bioavailability and Biogeochemistry Component (BBC), which is to develop the knowledge base and field indicators to help assess the consequences of changes in pollutant chemical form. Most organic and inorganic pollutants relentlessly change chemical form due to biogeochemical processes; the form(s) in turn define both toxicity and bioavailability. Thus, the BBC will complement the Biological Responses to Contaminants (BRCC) and Ecosystem Indicators (EIC) components of the PEEIR. Please see http://www.bml.ucdavis.edu/peeir/ for more information and complete list of investigators.

Development of Ecotoxic Indicators in Fish for Se TMDL Regulation in the San Francisco Bay-Delta and San Joaquin River (T.W.-M. Fan, R.M. Higashi, S. Teh, and P. Green).

Splittail fish are on the "threatened" list in the San Francisco Bay-Delta Estuary, and this project examines the biochemical and histological basis of reproductive impacts of selenium in this and other species. Selenium effects are complex because the effects are expressed through accumulation of unknown forms of selenium via the food chain. A culture of splittail has been established at UC Davis, which enables direct research on this wildlife of concern, rather than reliance on model species. One of the key hypotheses being tested is that of proteinaceous selenium as a marker of ecotoxic risk.

The Application of Toxicogenomics in Aquatic Toxicology Testing: A Pilot Study (Teh).

Chemically-induced toxicity is often preceded by or results in alterations in gene expression patterns and these changes can be used as a highly sensitive, characteristic, and informative biomarker for toxicity. Chronic selenium exposure has growth and reproductive effects in the adult fish and produces pathology and teratology in developing embryo at maternal doses of approximately 15-20 µg.g-1. The principal objective of this pilot study is the application of toxicogenomics in aquatic toxicology testing using a sensitive medaka (Oryzias latipes) fish model. The aim is to identify specific changes in gene expression associated with dietary selenium exposure (0.7, 10, 20, 30, 40, and 60 mg/kg purified casein (PC) diet), in liver and embryos (stages 11, 17, 25, 34 and 36 (hatchling) from exposed adult male and female medaka. Dr. Kayoshi Naruse (principal investigator of the Medaka EST project at University of Tokyo), in his visit to our medaka culture and experimental laboratory in June 2002, stated his interest to collaborate and to supply the expressed sequence tags (ESTs) to support this study. Thus far, he has provided us with 103 unique cDNAs (as ESTs), involved in transcription (24), heat shock (25), phase I and phase II metabolism (6 cytochrome P450s), tumor suppression (8), DNA replication and repair (9), apoptosis (1), vitellogenesis (2), and housekeeping (28) have been requested. To ensure that growth and cellular response to selenium toxicity is also examined, we have requested additional ESTs from Dr. Naruse, including fibroblast growth factor, growth-arrest specific protein, glutathione transferase, glutathione peroxidase, superoxide dismutase, and cystolic selenoprotein. Additionally, ESTs coding for other apoptosis-associated proteins have also been requested: bcl-2-associated protein x, apoptotic proteinase-activating factor, Fas receptor, and apoptotic cell death regulator DAD1. Working with Drs. Buckpitt and Bartosiewicz (UCD), a cDNA microarray, constructed using these ESTs will then be used as a target to assess mRNA levels in liver and embryos from adult medaka exposed to a full range of selenium. The success of this pilot study will provide a powerful tool in identifying and characterizing changes in gene expression associated with toxicity or carcinogenicity and could be the foundation for a fundamentally new genetic biomarker approach in aquatic toxicology testing. Simultaneous assessment of multiple toxins will be possible with this novel method and could greatly facilitate future aquatic environmental toxic exposure evaluation.

Chronic Toxicity of Environmental Contaminants in Sacramento Splittail (Pogonichthys macrolepidotus): A Biomarker Approach. (Hung, Teh, and Davis).

The maintenance of a population of fishes is heavily influenced by the constantly changing physical and biological conditions of the ecosystem. Contaminant stress may compromise the ability of fish to survive natural environmental stressors. Ultimately, fish populations that are unable to compensate for additional stress will show reductions in growth, reproductive capacity, and survival. For a species that has already declined drastically, survival and reproductive success have profound ecological significance. When exposed to various stressors such as from contaminants, the fish may not even survive to carry out the ultimate function of reproduction. Furthermore, chronic dysfunctions of reproduction in the surviving fish might ultimately result in decreased fecundity and fertility, and thus indirectly impacting the population level. Although water quality deterioration, water diversions, habitat loss, and degradation (all resulting from human activity) may have contributed to declines in fish population, there is a high degree of certainty that splittail population is adversely affected by exposure to contaminants from commercial, domestic, and agricultural sources. However, integrated laboratory and field investigations using biomarker approach to detect and quantify chronic contaminant responses in splittail are lacking.

The Sacramento splittail (Pogonichthys macrolepidotus), a Federally listed threatened species, forages on benthic organisms. Splittail are now largely confined to the Sacramento-San Joaquin Delta, Suisun Bay, Suisun Marsh, the Napa River, and the Petaluma River except during spawning migrations in winter and spring (Meng and Moyle, 1995). Juvenile remain in the river system for weeks to a year before migrating to the delta where they mature at age two. Adult fish remain in the bay-delta system year round but will migrate upstream to spawn in fresh water preferably over flooded vegetation. Unlike other native fish species where laboratory culture is difficult and expensive, splittail is easily cultured at low cost and will spawn in captivity providing access to all life stages. Therefore, we propose to use splittail as a native fish model for chronic toxicity study.

We will demonstrate the use of biomarkers (biological responses), in conjunction with ongoing biomonitoring efforts of fish population by DFG and water, sediment, and tissue contaminant monitoring by SFEI and USGS, to evaluate the chronic effects of contaminants on the health of splittail under laboratory and field conditions. Four functional categories of biological indicators will be measured: 1) indicators of contaminant exposure, 2) indicators of general condition indices, 3) indicators of organ and reproductive dysfunction, and 4) indicators of individual-level response. We propose to evaluate a suite of biomarkers of exposure and effect indicators at several levels of biological organization to quantitatively: 1) assess the potential chronic effects of contaminant exposure on various life stages of splittail under laboratory and field settings, 2) establish a link between the contaminant exposure and the deleterious health (growth and reproduction) of individual splittail, and 3) identify indicators of contaminant exposure that are most cost-effective for use in future monitoring studies. This will provide valuable information for future environmental compliance and regulatory studies and the ecological risk assessment process. These studies also have practical application as laboratory data linking specific contaminants with adverse chronic effects (as well as field data correlating biomarker expression with contaminant exposure) that could help guide management decisions with respect to determining acceptable contaminant levels in the environment.

Development of a Chronic Effect Sediment Toxicity Test Using Enzymatic, Immunologic and Histopathologic Biomarkers. (Kok-Leng, Tay, MacDonald, Doe, Teh, Lee ).

Sediments are an important ecological component of the ecosystem. They serve as a sink and as a natural reservoir for both point and non-point sources of contaminants introduced into aquatic environments. Sediment contaminants can be toxic to aquatic biota and can trigger chronic biological responses in sensitive species causing adverse effects on populations and communities. Bioaccumulation of contaminants by edible species can trigger serious human health issues. The objective of this study is to identify a suite of ecologically valid and cost-effective biomarker analyses to complement recommended Canadian methods for measuring toxicity of marine sediments. The focus will be biomarkers of effect, especially those at higher levels of biological organization such as histological and enzyme histochemical markers.