Theses and Dissertations

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Defense Date

8-2011

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

Donald S. McCorquodale

Second Advisor

David W. Kerstetter

Third Advisor

Curtis M. Burney

Abstract

This study examined mercury and methylmercury concentrations in shark species in order to determine differences between shark species and between locations. Stable isotope ratios were determined to see if interaction existed between approximate trophic level and mercury concentrations. Sharks were sampled from Florida Bay where muscle tissue biopsies and blood samples were extracted upon capture. Stable isotope ratios for carbon-13 (δ13C) and nitrogen-15 (δ15N) from freezedried blood samples were compared with levels of organic and inorganic mercury species from tissue samples in seven different shark species, focusing on blacknose, blacktip, bull, and lemon sharks. Pre-caudal length (PCL) was strongly correlated to mercury concentration and δ13C but not with δ15N. Ratios of δ15N between shark species were in agreement with observed trophic-level behavior of blacktip sharks feeding on blacknose sharks, indicated by greater values for δ15N ratios in blacktip sharks. Calculated length-normalized stable isotope ratio values correlated strongly to values for mercury concentrations in blacktip sharks, indicating a potential method for forecasting inorganic or organic mercury concentrations without the use of more expensive mercury tests. This calculation also provided validity for a new metric involving the use of stable carbon isotope ratio divided by length (PCL) to be compared with other metrics. Correlations between δ15N values and mercury values indicate some level of interaction between trophic level and quantity of mercury contaminants in shark muscle tissue.

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