A Survey of Algal Epiphytes from Vallisneria americana Michx. (Hydrocharitaceae) in the Lower St. Johns River, Florida

Epiphytic algae may be responsible for a significant amount of primary productivity in aquatic ecosystems, but also reduce available light, compete for nutrients, and increase drag on their living substrates. A survey of the epiphytic algal community of the submersed aquatic macrophyte Vallisneria americana Michx. (Hydrocharitaceae) in the lower St. Johns River, FLwas conducted over a 17-month period. A total of 122 infrageneric taxa were collected at four sites along a 93-km stretch of the river, yielding 32 diatoms (Bacillariophyta), 42 green algae (Chlorophyta), 45 blue-green algae (Cyanobacteria), 2 euglenoids (Euglenophyta), and 1 dinoflagellate (Pyrrophyta) taxa identified over the study period. However, only diatoms and cyanobacteria were seen at all sampling dates, and only a Cocconeis sp. was identified at all sites on all dates. This study provides baseline survey data of the epiphytic algal community in order to assess future anthropogenic effects.