Zooplankton feeding ecology and the experimental acidification of Little Rock Lake
There is considerable variety in both the selective behavior of suspension feeders and the quality of food available to them. The author reviews this variability and incorporate it in a simple model of particle selection that quantifies the consequences of selective feeding under various feeding conditions. To evaluate the concept that selective feeding enhances fitness, the author tests the hypothesis than an herbivorous zooplankton selects food items that best support its reproduction. Investigations of zooplankton herbivory in experimentally acidified Little Rock Lake indicate that acidification from pH 6.2 to pH 5.2 has not directly impaired feeding rates, while effects on selective feeding behavior are evident. Assessment of the effects of lake acidification on large predatory zooplankton indicate that Chaoborus spp. and water mite populations remain as yet unaffected, while Epischura lacustris and Leptodora kindtii have both declined in the acidified basin. Methodological tests show that preservation of labelled zooplankton by rapid freezing on dry ice minimizes loss of sup 14C and sup 32P. sup 14C retention approximates 100\%, while sup 32P retention is more variable.