Chlorinated pesticides, polychlorinated biphenyls, and dioxins in colonial nesting waterbirds of Galveston Bay, Texas

Abstract

Eggs of geotropic cormorants (Phalacrocorax brasilianus), black-crowned night-herons (Nycticorax nycticorax) and great egrets (Ardea alba) were collected from a herons located in Alexander Island, near the Houston Ship Channel, in Galveston Bay. Eggs of geotropic cormorants were also taken from three additional islands in Galveston Bay, and from two locations outside the bay. Each egg was analyzed for persistent organochlorine pesticides (i.e. DDTS, chlorates, HCHs), and polychlorinated biphenyls (PCBs). Selected eggs were also analyzed for polychlorinated dibenzo-p-dioxins (PCDD), and polychlorinated dibenzofurans (PCDF) to determine differences and similarities in the accumulation of these contaminants among species, and to evaluate potential impacts on reproduction. A H4IIE rat hepatoma cell bioassay containing a luciferase reporter gene was conducted on selected extracts to determine TCDD- equivalents (TCDD-EQS) and compare these values with the toxic equivalents (TEQs) calculated from instrumental analysis. DDE concentrations were higher in eggs of geotropic cormorants from control locations outside the bay than inside the bay, possibly due to different regional sources. Predominant PCB congeners in the three species were 153, 138, 180, 118, 99, 187, and 170. These congeners comprised between 56 and 68% of the total PCB load in the samples. Mean total PCB concentrations were higher in geotropic cormorant eggs from Alexander Island than in eggs from areas farther away from the Houston Ship Channel, including control areas outside the bay. PCB 126 was highest in eggs of geotropic cormorants from Vingt-et-un and Smith Point Islands within Galveston Bay. 2,3,7,8 TCDD was the only dioxin detected in eggs from all locations within Galveston Bay. TEQ concentrations in eggs ranged from 67 pg/g at the control site to 452 pg/g at Alexander Island. TCDD-EQ concentrations were highest in eggs (437 pg/g and 413 pg/g, respectively) of cormorants from Vingt-et-un and Smith Point Islands. Overall, DDE, PCBs, 2,3,7,8 TCDD, TEQ, and TCDD-EQ concentrations were below levels known to affect reproduction. No identifiable deformities or abnormalities were detected in any of the eggs analyzed. Reproduction of birds nesting on Alexander Island in 1996 (approximately 1 chick fledged per nest) was considered normal.