TRACE ELEMENTS IN THE AQUATIC BIRD FOOD CHAIN AT THE NORTH PONDS, TEXACO REFINERY CASPER, WYOMING

The objectives of this study were to determine nesting success of aquatic birds, trace element concentrations in the aquatic food chain, and whether trace elements were biomagnifying through the aquatic food chain of ponds at the inactive Texaco Refinery, in Evansville, Wyoming. Trace element concentrations in samples collected from the Texaco Refinery were compared to those found in samples collected from a background site, Pathfinder National Wildlife Refuge. The ponds at the inactive refinery provided a source of water to aquatic birds in an otherwise arid landscape. Nesting success for shorebirds using an island in Pond 1 was greater than 90%. Waterfowl used Pond 1 mainly to feed rather than for nesting. Little nesting activity was observed for waterfowl and shorebirds at Pond 2, but shorebirds were consistently observed feeding and resting there. Trace elements in water samples from Ponds 1 and 2 were not at concentrations that could adversely affect feeding and nesting aquatic birds. Chromium was slightly elevated in sediments and in some vegetation and avian egg samples from both ponds relative to background concentrations. However, the potential for these concentrations to affect aquatic birds is unknown. Arsenic was slightly elevated in some sediment samples from both ponds but concentrations were comparable to background concentrations. Boron and selenium were slightly elevated in vegetation samples, and selenium was also slightly elevated in avian egg samples. Both boron and selenium are naturally occurring in the area which would explain the slight elevations found in the biological samples. There was no indication of significant bioaccumulation of any trace elements in the aquatic food chain