Spatial and Seasonal Distribution of Littoral Diatoms in Yaquina Estuary, Oregon (USA)

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Abstract
Distributional patterns of littoral diatoms in Yaquina Estuary, Oregon (USA) were related to selected environmental variables. Seven stations located between marine and fresh water were sampled during May and Aug. 1969 at 4 levels in the intertidal region. Mean species diversity was lowest at marine and fresh-water stations subjected to prolonged periods of desiccation. The most abundant taxa were Melosira moniliformis, Navicula mutica, Synedra fasciculata, and Navicula no. 2, a Schizonema-type Navicula. Of these, N. mutica had the narrowest distribution to the pattern of sampling. Multiple correlation of a community difference measure (Dhk) with selected physical variables indicated that mean salinity accounted for most of the variability between samples. Matrices of Dhk values comparing stations along the salinity gradient supported the concept of a distributional continuum in the estuary with a pronounced discontinuity in the diatom flora at locations where the salinity fluctuates around a mean of 5.permill.. The distributions of Achnanthes spp., Amphipleura rutilans, Fragilaria striatula var. californica, Licmophora gracilis, M. moniliformis, M. nummuloides, Navicula diserta, N. mutica, N. viridula var. avenacea, Navicula no. 2, Nitzschia frustulum var. perpusilla and S. fasciculata are discussed in detail.