PARENT SESSION
Poster Session # 17: Aquatic Systems.

Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Is coarse woody debris a refuge for attached algae in sandy coastal plains streams?

Miller, Stephanie^*,1, Maloney, Kelly^*,1, Mitchell, Richard^*,1, Feminella, Jack¹, ¹ Auburn University, Auburn, AL

ABSTRACT- Shifting sands in small coastal plains streams provide an unstable, abrasive, and potentially inhospitable habitat for benthic organisms, especially during spates. Coarse woody debris (CWD) can reduce the impact of physical disturbance on organisms by reducing sand particle movement and thus stabilizing the streambed. We compared algal biomass (as chlorophyll a) and diatom composition on sand versus submerged CWD substrates in 11 small coastal plains streams at Fort Benning, GA. Physicochemical habitat variables, including CWD abundance and streambed stability also were quantified. Algal biomass on sand was higher in streams containing high CWD. Although algal biomass on CWD was highly variable, diatom diversity and richness were higher on CWD than on sand. Average length of diatom cells also was higher on CWD than sand substrates because of a greater proportion of larger species occurring on CWD, and diatom cells on sand in high-CWD streams were larger than cells in sand substrates in low-CWD streams. Scanning electron microscopy revealed that crevices and outer surfaces of sand grains contained mostly adnate, short chains of the diatom Eunotia, whereas a more diverse diatom assemblage occurred among deep crevices and pits on CWD surfaces. These observations suggest that CWD not only serves as a substrate-stabilizing factor in coastal plains streams, but also may provide a refuge for large diatom species ill-adapted to hydrologic disturbance.

Key words: diatom, disturbance, coarse woody debris, streams