Variation of the phytoplankton structure in Puerto Don Juan, Bahia de Los Angeles, Baja California

Abstract

A time series with samplings every two hours was generated, on surface and at 5 m depth from august 6th to the 12th of 1986 in a fixed station at Puerto Don Juan (Bahía de Ios Angeles). Subsurface aimed trawlings were carried out with a conic standard mesh of 75 µm of flux and reflux from the centre of the lagoon to the inner mouth. A taxocenosis composed of 242 taxa was found, which is divided in 86 genera, 223 species, 27 varieties and 6 forms. Puerto Don Juan presented abundances in values which are very high for the whole phytoplanktonic structure. During spring tides, the phytoplanktonic structure was found to be distributed homogeneouslly in the water column, and when the tide amplitude decreased some differences were detected between the two depths under study due to the stratification of the environment. During the sampling period it was found that the dominant species stayed in the lagoon even the daily changes, and the non dominants depended on the environment changes. The best indicator of the fluctuation in the lagoon phytoplanktonic structure in terms of taxonomic leve1 is constituted at genus level.