William B. Perry

Patterns of Microhabitat Use Among Four Species of Darters in Three Appalachian Streams

-We used snorkeling techniques to examine patterns of microhabitat use among four species of darters-Etheostoma flabellare, E. blennioides, Percina gymnocephala and the potentially threatened E. osburni-in three West Virginia streams. Sympatric darter species were generally segregated in each stream, based on microhabitat use variables of mean depth, current velocity and substrate type. In all three streams-the East Fork of the Greenbrier River, the Cherry River and Laurel Creek-E. osburni was observed in fast current velocities and rock substrate in water depths ranging from 20 to 30 cm. In the East Fork of the Greenbrier River and Laurel Creek, E.fiabellare was common in slower velocities over predominantly cobble substrate. Percina gymnocephala and E. blennioides were spatially segregated from E. osburni on the basis of water column depth. Differences in habitat use may be related to morphological differences between species.

CRITICAL PROBLEMS WITH EXTRACTION OF ATP FOR BIOLUMINESCENCE ASSAY OF PLANKTON BIOMASS

Recovery of ATP by boiling tris extraction was 90–95 percent greater in 1 liter grab samples than in concentrated net samples. ATP losses were attributed to insulating effects promoted by accumulation of detritus on filters. A series of extractions over a concentration range of whole or size-segregated plankters and cultured algae was made to determine volume of water to be filtered for optimum extraction efficiency. Accuracy of ATP assays was optimized by: (i) using large diameter (i.e. 47 mm) acetate filters; (2) limiting sample volume filtered to 50 ml when particulate organic carbon (POC) exceeded 0.4 mg l−1; and (3) performing extractions in boiling tris maintained initially on a laboratory hot plate at 400°C as opposed to hot water bath at 100°C.Additional problems were encountered in using published cellular carbon: ATP ratios for conversion of ATP data to biomass as carbon. Ratios of POC: ATP in cultures of sheathed blue-green algae reached 550 : i, while non-sheathed forms yielded ratios near values previously reported for plankton communities. Difficulties in applying a uniform conversion factor may be expected in plankton communities containing significant volumes of sheathed blue-greens.