Geology topics
C.A. Bishop
Publications and source records attributed to C.A. Bishop.
Epilogue: Lessons yet to be learned
This chapter provides a summary of the book Ecotoxicology of Amphibians and Reptiles edited by Sparling, Linder and Bishop. In addition to the comparative lack of information on effects and residue burdens of known contaminants in amphibians and reptiles, there is a plethora of new chemicals being produced and released into the environment on which no data exist at all. According to the Environmental Defense Fund, there are some 75,000 chemicals produced each year, not including pesticides. Of these, 3,000 are produced in high volumes. Of the high volume chemicals, only 29% have been examined for effects of human health and only 5% have been examined for effects on the environment and wildlife. Even of these 150 chemicals, only a small handful have been examined in amphibians or reptiles. Thus there is a tremendous lack of information on the effects of environmental contaminants on these vertebrates. This chapter outlines the major research needs in the area of ecotoxicology of amphibians and reptiles and lists several reasons why these animals would make excellent subjects for monitoring the effects of contaminants.
The current status of amphibian and reptile ecotoxicological research
The extent of research conducted on the effects of contaminants on reptiles and amphibians has been scant compared to that of other vertebrate classes including fishes, birds and mammals. In a review of literature from 1972 until 1998 we found that only about 2.7% of the papers published on ecotoxicology in vertebrates concerned amphibians and 1.4% for reptiles. Most studies on amphibian ecotoxicology were on metals, pesticides, and acid deposition. For reptiles the greatest frequency of papers included metals, organochlorines, and others. In proportion to the taxonomic importance, far more papers were written on turtles than on other reptile orders. Most of the papers dealt with residues and very few dealt with effects of contaminant exposure.
Polychlorinated biphenyl residues and egg mortality in double-crested cormorants from the Great Lakes
We evaluated the overall potency of polychlorinated biphenyl (PCB)-containing extracts from double-crested cormorant ( Phalacrocorax auritis ) eggs with an in vitro bioassay system, the H4IIE rat hepatoma cell bioassay. Results from the H4IIE bioassay were strongly correlated with the hatching success of eggs in the colonies, whereas conventional methods of PCB analysis correlated poorly with hatching success of eggs from the same colonies. These observations suggest that even though concentrations of total PCB residues have declined in almost all compartments of the environment, their effects are still being observed. The significance of this observation is that the adverse symptoms presently observed in certain Great Lakes fish-eating waterbird populations do not appear to be caused by some as yet unidentified industrial chemical or chemicals and seem not to be the result of pesticides, but rather to the dioxin-like activity of PCBs. Evidence is presented to suggest that the relative enrichment of the potency of PCBs in the environment may play a role in the persistence of the observed adverse symptoms.