Masters Theses

Date of Award

5-1999

Degree Type

Thesis

Degree Name

Master of Science

Major

Ecology and Evolutionary Biology

Major Professor

David A. Buehler

Abstract

I collected eggs and chicks from four great blue heron (Ardea herodias) colonies on and around the Oak Ridge Reservation, Tennessee, in 1993 and 1994. I analyzed eggs for both PCB and mercury levels, while also measuring a suite of biomarkers aimed at exposing biological effects of these contaminants. Chicks were necropsied, and muscle, liver, feather, and fat samples were collected for contaminant analysis. A group of biomarkers was also examined to ascertain any effects of these contaminants on growing chicks. Reproductive output was also monitored in an effort to correlate it with contaminant loads at specific sites. Fish collected at the colonies were also examined for PCB and mercury content.

The K-25 colony was located closest to the sources of contaminants; the Melton Hill colony was on the Oak Ridge Reservation, but upstream from contaminants. The Long Island colony was located >15 km from Oak Ridge and the Looney Island colony was located on Fort Loudon Lake, >15 km from Oak RidgeEggs from Melton Hill had lower mercury concentrations than eggs from K-25 (P ≤ 0.05). No other colonies differed. PCB concentrations were higher in eggs from K-25, when compared to eggs from Long Island and Looney Island (P ≤ 0.05). The only biomarker that differed between colonies was circumference (P ≤ 0.05), which was greatest in the K-25 colony.

In chicks, liver, muscle, and feathers showed differences between colonies for mercury concentration (P = 0.0002, 0.0996, and 0.0002, respectively). Overall, K-25 samples showed the highest concentrations, when compared to the other colonies. Total PCB concentrations in chicks also differed between colonies in both muscle and fat samples (P = 0.0373 and 0.0396, respectively), with the highest concentrations coming from the K-25 colony. same was true for PCB congener 1260 in fat, muscle, and liver samples (P = 0.0099, 0.0069, and 0.0275, respectively).

The only biomarker to differ marginally between colonies was the liver enzyme, MPRO (P= 0.0630). The activity of this enzyme was lowest in the K-25 colony. The other biomarkers, including another liver enzyme, did not differ between colonies.

The highest mean clutch size (X = 3.71, n=17) was found in the Melton Hill colony. The lowest clutch size (X = 3.19, n = 32) was found in the Looney Island colony. Overall, it appears that clutches were larger in on-site colonies than they were in off-site colonies. Mean mortality (chicks lost/nest) was highest in the Looney Island colony (x = 0.67), and lowest in the Long Island and Melton Hill colonies (x = 0.44 for both).

PCB concentrations in fish did not differ between sites, although, mercury concentrations differed in fish (P = 0.03). Fish from on-site colonies had mean mercury concentrations of 0.06 0.02 ppm, while fish from off-site colonies had a mean level of 0.02 ± 0.00 ppm.

Results indicated that clutch sizes from these colonies were comparable to those reported by other researchers across North America. Contaminant loads found in this study are below those reported by other investigators in areas where bird populations show measurable effects from these contaminants. It appears that the contaminant levels found in this study are not adversely affecting reproduction, growth, or survival.

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