T4 AM Endangered Species and Environmental Contaminants: Status of the Science (Part 1)
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in Ballroom 4

(SKO-1117-754751) ESA-listed species and other practical complications for population-based water quality criteria.

Skorupa, J¹, Boroja, M², ¹ U.S. Fish and Wildlife Service, Arlington, VA, USA² National Marine Fisheries Service, Silver Spring, MD, USA

ABSTRACT- Currently, water quality criteria are conceptually tied to threshold points for toxic effects on individual test organisms. However, regulatory criteria tied to individual level effects are viewed as unnecessarily restrictive by some, because such criteria would often not fully utilize species demographic assimilative capacities (DAC). Subsequently, the maximum capacity to pollute receiving water bodies without causing population level effects would also not be fully utilized. The pursuit of less restrictive criteria based on DAC and population level risk is very alluring to regulatory agencies under intense pressure to minimize regulatory impacts on commerce. However, many of the practical implications of basing criteria on population level risk management have received little recognition and discussion. For example, one of the inherent premises of population-based criteria is that some determinate number of individuals is expendable. This premise is violated when every individual of a species counts. For ESA-listed aquatic and aquatic-dependent species, in fact, every individual does count both in a legal sense and biologically (given the ESA goal of maximizing a species recovery potential). Thus, population-based criteria are inimical to the conservation of ESA-listed species. Another apparently hidden premise is that the full DAC would be available for allocation to every pollutant requiring the derivation of water quality criteria. This premise is plainly intellectually bankrupt. If even a few pollutants co-occurred in space and time under this scenario, population collapse would be the inevitable and unavoidable outcome of pollution at criteria levels. These and other conceptual complications associated with population-based water quality criteria will be presented and discussed. The considerations we present lead to the conclusion that individual level toxic thresholds are the appropriate foundations for water quality criteria and that limited research resources would best be allocated toward producing additional individual level toxicity data for far more test species and far more test chemicals, as opposed to investing resources in ill-fated attempts to develop a population-based foundation for water quality criteria.

Key words: ESA-listed species, water quality criteria, demographic assimilative capacity