Tissue distribution of organochlorine pesticides in largemouth bass (Micropterus salmoides) from laboratory exposure and a contaminated lake

Abstract

Tissue concentrations of persistent organochlorine pesticides in laboratory-exposed largemouth bass (Micropterus salmoides) and in bass collected from Lake Apopka, FL were determined by both total mass and lipid normalized mass to better understand the bioaccumulation pathways of contaminants. In the laboratory study, male bass were orally administered a single dose of a mixture of two pesticides (p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and dieldrin) and then fed uncontaminated food for 28 days. Gastrointestinal tract, liver, brain, gonad, kidney, spleen, and muscle were collected for chemical analysis. Different profiles were observed by total contaminant mass in tissues compared to lipid normalized mass. On a lipid normalized basis, p,p'-DDE was highest in the gastrointestinal tract followed by the liver, gonad, spleen, muscle, kidney and then brain. Dieldrin, on the other hand, was highest in the gastrointestinal tract and spleen and then followed by the gonad, muscle, liver, kidney, and brain. Distribution of the chemicals among the organs differed by their log KOW values and generally followed the blood flow path after the gastrointestinal tract. The low contaminant levels found in kidney and brain suggest insufficient time for equilibration into these tissues, especially into the brain where the blood-brain barrier may be slow to traverse. In Lake Apopka fish, dichlorodiphenyltrichloroethanes (DDXs, sum of p,p'-DDE, p,p'-DDD, and p,p'-DDT), Drins (sum of aldrin, dieldrin, and endrin), and hexachlorocyclohexanes (HCHs) were found. For DDXs, the lipid normalized concentrations in each tissue were about the same, as predicted from theory. For Drins and HCHs, the lipid normalized concentrations were similar for kidney, spleen, brain, gonad and muscle, but much lower in the gastrointestinal tract and liver, probably because of metabolism occurring in those tissues.

Keywords: Lake Apopka; Largemouth bass; Oral dosing; Organochlorine pesticides; Tissue concentration.

Figure 1

Tissue concentrations of p, p’-DDE and dieldrin in largemouth bass following the oral dosing in laboratory experiments. Contaminant levels are based on A) fresh weight (µg/g ww) and B) lipid weight (µg/g lipid). Values are means of 5 replicates and error bars indicate standard deviation of mean tissue concentrations.

Figure 2

Tissue concentrations of OCPs detected in wild-caught largemouth bass from Lake Apopka, FL. Contaminant levels are based on A) fresh weight (ng/g ww) and B) lipid weight (ng/g lipid). Values are means of 5 replicates and error bars indicate standard deviation of mean tissue concentrations. (DDXs = p, p’-DDE + p, p’-DDD + p, p’-DDT; Drins = aldrin + dieldrin + endrin, HCHs = α-HCH + β-HCH + γ-HCH + δ-HCH)

Figure 3

Composition of DDT related compounds in different tissues of wild-caught largemouth bass from Lake Apopka, FL. Composition was calculated as the percent of total concentration of each DDT congeners. Levels of p, p’-DDT, if detectable at all, were insignificant.