The relationship between land use and emerging and legacy contaminants in an Apex predator, the bottlenose dolphin (Tursiops truncatus), from two adjacent estuarine watersheds

Abstract

Background: Persistent organohalogen contaminant (POC) exposure is of concern in marine mammals due to the potential for adverse health effects. Studies have examined POCs in marine mammals on a regional scale; however, limited data exists on POC concentrations relative to land use and watersheds.

Objective: Examine geographical variation of POC concentrations in bottlenose dolphins as it relates to land, and watershed, use.

Methods: POC (PCBs, DDTs, and PBDEs) concentrations were measured in blubber of bottlenose dolphins (n= 40) sampled in estuarine waters near Charleston, SC. Photo-identification sighting histories were used to assess the dolphins' use of estuarine waters in two adjacent watersheds (Cooper Subbasin and Stono Subbasin) in the study area and to determine land use (developed, forested, agriculture, and wetland) associations.

Results: Dolphins with ≥ 75% of their sightings in the Cooper Subbasin, which is characterized by a higher degree of developed land use, exhibited higher levels of PCBs, PBDEs, and total pesticides than those with ≥ 75% of their sightings in the Stono Subbasin. Observed differences were significant for ΣPBDEs and ΣDDTs/ΣPCBs ratio. Significant positive correlations were observed between ΣPBDEs and developed land use and between ΣDDTs/ΣPCBs and wetland land use. A significant negative correlation was observed between ΣDDTs/ΣPCBs and developed land use.

Conclusion: The spatial pattern of PBDEs and the ΣDDTs/ΣPCBs detected in dolphin blubber was shown to vary significantly with adjacent watersheds and land use associations.

Keywords: Apex predator; Bioaccumulation; Bottlenose dolphins; Land use; Persistent organohalogen compounds (POC); Spatial distribution; Watershed.