Genotoxicity in native fish associated with agricultural runoff events

Abstract

The primary objective of the present study was to test whether agricultural chemical runoff was associated with in-stream genotoxicity in native fish. Using Sacramento sucker (Catostomus occidentalis), we combined field-caging experiments in an agriculturally dominated watershed with controlled laboratory exposures to field-collected water samples, and we coupled genotoxicity biomarker measurements in fish with bacterial mutagenicity analysis of water samples. We selected DNA strand breakage as a genotoxicity biomarker and Ames Salmonella mutagenicity tests as a second, supporting indicator of genotoxicity. Data from experiments conducted during rainfall runoff events following winter application of pesticides in 2000 and 2001 indicated that DNA strand breaks were significantly elevated in fish exposed to San Joaquin River (CA, USA) water (38.8, 28.4, and 53.6% DNA strand breakage in year 2000 field, year 2000 lab, and year 2001 field exposures, respectively) compared with a nearby reference site (15.4, 8.7, and 12.6% DNA strand breakage in year 2000 field, year 2000 lab, and year 2001 field exposures, respectively). Time-course measurements in field experiments supported a linkage between induction of DNA strand breakage and the timing of agricultural runoff. San Joaquin River water also caused significant reversion mutation in two Ames Salmonella tester strains. Salmonella mutagenicity corroborated in-stream effects, further strengthening a causal relationship between runoff events and genotoxicity. Potentially responsible agents are discussed in the context of timing of runoff events in the field, concordance between laboratory and field exposures, pesticide application patterns in the drainage, and analytical chemistry data.

Cage Exposure of European Sea Bass (Dicentrarchus Labrax) for in Situ Assessment of Pollution-Related Genotoxicity

“…Their DNA damage was 1 to 1.5 times higher than in fi sh from the unpolluted site (48). One to fi ve times higher rate of DNA strand breaks was measured in the erythrocytes of caged Sacramento sucker (Catostomus occidentalis) after one week of exposure in waters receiving agricultural chemical runoff (14). Caged chub (Leuciscus cephalus) liver cells showed a two fold increase in DNA damage after four weeks of exposure to contaminated river water (15).…”

“…Several studies have investigated the genotoxic effects of polluted aquatic environments on fish species, either through the sampling of native populations (6,(9)(10)(11)(12)(13) or by cage exposure in situ (14)(15)(16). When assessing the impact of pollution in aquatic environments using native fi sh populations, research may be compromised by migration of fi sh for feeding and breeding, availability of certain species at a particular site of interest, or diffi culty to obtain enough specimens for desired analyses.…”

“…There have not been many studies using transplanted (caged) fi sh for genotoxicity assessment, and most of them involved freshwater species (14,15,24,25). Studies using caged fish in marine environment include the research work assessing the infl uence of the Laranjo basin (Aveiro, Portugal) contamination on caged golden grey mullet (Liza aurata) by measuring erythrocyte nuclear abnormalities (16) and the study of genotoxic response in caged eel (Anguilla anguilla) after exposure to harbour waters by observing DNA integrity and nuclear abnormalities in erythrocytes (26).…”

Cholinesterases in Aquatic Biomonitoring: Assay Optimization and Species-Specific Characterization for a California Native Fish

“…Field caging exposure C. occidentalis were caged during January/February 2000 in rivers of the heavily agriculturalized watershed of California's Central Valley according to the experimental design previously described (Whitehead et al, 2004). Briefly, exposures were timed to coincide with runoff from the first major rainstorm event following winter-season application of insecticides to orchards.…”

“…C. occidentalis are an appropriate model for this system since they are one of only a few native species still abundant in the Central Valley, and our data indicate that they are relatively sensitive to ChE inhibition. Although invertebrate species are often most sensitive, recent evidence indicates that pesticide contamination can have direct sublethal effects in vertebrates (Scholz et al, 2000;Moore and Waring, 2001) including C. occidentalis (Whitehead et al, 2004). We applied ChE activity determinations during field experiments to test whether C. occidentalis were exposed to toxic concentrations of pesticides during rainstorm runoff events following applications to orchards.…”