ZOOPLANKTON BODY SIZE AND COMMUNITY STRUCTURE - EFFECTS OF THERMAL AND TOXICANT STRESS

Episodic heat waves and an increase in pesticide use are widely cited as consequences of climatic warming. Recent studies show that these st ressors often cause declines in the mean body size of zooplankton. Res ults from laboratory and field studies, as well as observations from b oth thermal- or toxicant-stressed natural systems, show (1) reductions in mean body size within stressed populations, or (2) changes in comm unity composition that favor small-bodied over large-bodied species. D uring the past decade, it has become widely accepted that a shift in z ooplankton body size can dramatically affect water clarity, rates of n utrient regeneration and fish abundances. Thus, climatic warming and a ssociated change in pesticide use has the potential to cause striking change in the structure and functioning of temperate-zone lakes.