Structural characteristics of a diatom community epiphytic on Ruppia maritima

Epiphytic diatoms were collected from both the leaves and internodes of Ruppia maritima in a New Jersey salt marsh during the growing season of the host plant. Community diversity (H and the number of diatom taxa) values were initially high as Ruppia began its growth, but quickly dropped to sustained low levels as vegetative growth of the host ceased and new attachment sites were no longer available. A critical examination of all structural characteristics indicated that the leaves and internodes of Ruppia support a single, nearly homogeneous epiphytic diatom community. An analysis of variance indicated that differences between leaves and internodes were minimal, as did a comparison of the assemblages present on these two sites by a selected similarity index. A total of 57 taxa were encountered and the single dominant taxon was Navicula pavillardi, which accounted for one out of every three individuals counted. A comparison of the epiphytic diatom community with those inhabiting the sediments on the marsh proper revealed that the marsh sediments were the major source of individuals for Ruppia colonization.