Contaminant Exposure of Barn Swallows Nesting on Bayou D'Inde, Calcasieu Estuary, Louisiana, USA

Abstract

Current and historical point source discharges, storm water runoff, and accidental spills have contaminated the water, sediment, and biota within the Calcasieu Estuary in southwestern Louisiana. In 2003, barn swallow (Hirundo rustica) eggs and nestlings were collected beneath two bridges that cross Bayou d'Inde, the most contaminated waterway within the Calcasieu Estuary. Samples were also collected from a bridge over Bayou Teche, a reference site in south central Louisiana. Polychlorinated biphenyl (PCB) concentrations in barn swallow eggs and nestlings were significantly higher at the downstream site on Bayou d'Inde (2.8 micro g/g PCBs in eggs and 1.5 micro g/g PCBs in nestlings) than at the other two sites (< 0.2 micro g/g PCBs in eggs and nestlings at both sites). Ethoxyresorufin-O-dealkylase activity in nestling livers was significantly higher at the downstream site on Bayou d'Inde (50 pmol/min/mg) compared to the other two locations (24 pmol/min/mg, each), probably because of exposure to PCBs. Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran concentrations in eggs and polycyclic aromatic hydrocarbons in nestlings were at background concentrations at all sites. Trace element concentrations in barn swallow eggs and nestling livers were at background levels and did not differ among the three sites. A biomarker of DNA damage did not differ among sites.

Exposure of insects and insectivorous birds to metals and other elements from abandoned mine tailings in three Summit County drainages, Colorado

“…Those were Co and Zn and they increased in tandem with increases in insects (exposure), but again not to threatening or toxic levels. Geometric mean concentrations of Zn, for example, averaged 57 μg/g in this study which was similar to concentrations in swallows from CO, LA, MN, NV, RI, and WY (Custer et al 2001(Custer et al , 2002(Custer et al , 2003a(Custer et al , 2005(Custer et al , 2006a(Custer et al ,b, 2007a. Cobalt has rarely been measured in swallow livers, but it averaged 0.03 μg/g dry wt.…”

“…Cadmium and Hg were lower in Deer and Snake Creeks than at other swallow locations (Custer et al 2001(Custer et al , 2003a(Custer et al , 2005(Custer et al , 2006a(Custer et al , b, 2007a and were at background concentrations. In addition, histopathologic examination of kidney samples from the 36 swallows in this study did not reveal any significant changes that would indicate exposure to toxic levels of cadmium.…”

“…Both elements are known to be either rapidly metabolized in birds (As, Pendleton et al 1995) or are rarely detected in liver tissue (Ni, Custer et al 2002, 2003a, 2006b, 2007a. Of the remaining 13 essential elements, all except Cr, Rb, and V were at background concentrations in bird (Custer et al 2001(Custer et al , 2002(Custer et al , 2003a(Custer et al , 2005(Custer et al , 2006a(Custer et al , b, 2007a. Chromium (2.1 μg/g dry wt.)…”

“…Barium and Sr, two other non-essential elements, were at background levels (Custer et al 2002(Custer et al , 2003a(Custer et al , 2006a(Custer et al , b, 2007a for swallows. There are limited data available for interpreting avian concentrations of three other non-essential trace elements, Cs, Ga, and Th.…”

“…Additionally, because the food chain is short, from sediment to insects to birds, interpretation of the data is simplified and direct. Finally, contaminant accumulation and effects in tree swallows have been studied at multiple locations across the USA and Canada, so a body of information is available to help interpret data gathered at this location (Bishop et al 1995;Custer et al 2001Custer et al , 2002Custer et al , 2003aCuster et al ,b, 2005Custer et al , 2006aCuster et al , b, 2007aDeWeese et al 1985;King et al 1994;Kraus 1989;Shaw 1983).…”