Serra, M. W.. University of Valencia, manuel.serra@uv.es

LONG-TERM EFFECTS OF REDUCTIONS IN POPULATION GROWTH RATE ON THE PROBABILITY OF EXTINCTION OF ROTIFER POPULATIONS

Concentrations of pollutants causing adverse effects in aquatic ecosystems are mostly determined by short-term toxicity tests of 1-7 days. These data are used in ecological risk assessments to predict whether populations can endure certain exposures. An example is the two day rotifer reproductive test where the mean reduction in population growth rate (r) at the no observed effect concentration (NOEC) of 11 toxicants was 13% and 42% at the lowest observed effect concentration (LOEC). Even purportedly safe toxicant exposures (NOEC) reduced r by an average of 13%. It is not known whether rotifer populations can sustain such a reduction in population growth rate and survive long-term. We investigated this question using a new model of the dynamics of natural rotifer populations and quantified probabilities of extinction over 100 years. Even small reductions in r over the long termincreased a population's probability of extinction. For a 5% reduction in r, probability of extinction increased 10% over 100 years. Reductions in r of 10% and 20% increased the probability of extinction 30% and 70%, respectively. These effects are due to reductions in the resting egg pool size, allowing stochastic events to have greater influence on the population dynamics. These effects are not detected by current toxicity tests and not considered in ecological risk assessments.

Day: Friday, Feb. 5

Time: 10:45 - 11:00am

Location: Hilton of Santa Fe

Code: SS11FR1045H