The Seasonal Succession of Periphyton Communities on Different Sizes of Substratum in Juday Creek from December 1995 through July 1997
Berlin, Daniel J.
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Benthic algae are ideal indicators of the health of most aquatic ecosystems. They are primary producers in food webs and are the fundamental components in aquatic biogeochemical cycles. Not until recently has the study of algae shifted to periphyton (attached algae) in lotic habitats. A field experiment was conducted to determine the effect of rock size and seasonal influence on the biomass and taxonomic structure of the periphyton community in Juday Creek, IN. Samples were collected from all four seasons: December 1995, April 1996, June 1997, and July 1997. Chlorophyll a, ash free dry mass (AFDM), algal density, diversity, and individual abundance of genera were measured on six different substrate sizes, ranging in diameter from 0.06 mm to greater than 256 mm. Chlorophyll a, AFDM, and algal density increased during the winter and spring months and were highest on large cobble and boulder substrates (128-256 mm and >256 mm) (P < 0.05 for all three variables). Diversity indices were highest on boulder and large cobble substrates (P < 0.05). Some taxa predominated on large cobble and boulder all year while others thrived on these substrates only during the winter and spring. The results suggest that diatom growth-form may explain taxon-specific responses to disturbance (e.g. downstream tumbling) varying with different substrate sizes and seasonal changes throughout the year. Only one green alga, Cladophora, predominated in the winter and spring months on large cobble. Seasonal light intensity and algae physiognomy directly influenced the algal assemblage on different sized rocks in Juday Creek.