The surf-zone phytoplankton of the State of Sao Paulo, Brazil. I. Trends in space-time distribution with emphasis on Asterionellopsis glacialis and Anaulus australis (Bacillariophyta)

Abstract

The objective of this research was to assess the species composition and relative abundance of the surf-zone phytoplankton of 20 beaches in the State of Sao Paulo (23 degrees 20'-25 degrees S), Brazil, from August 2004 to July 2006. Once a month, surface hauls with a 20 mu m-mesh phytoplankton net were taken "simultaneously" (within an 8-hour period) at beaches of contrasting morphodynamics distributed along an 880km-long coastline. The most conspicuous trend, observed for both annual cycles, was the dominance or co-dominance of the known surf-diatoms Asterionellopsis glacialis and Anaulus australis at the more exposed beaches of the southern coast. The second trend observed was the dominance or co-dominance of other diatoms (Thalassionema nitzschioides, Pseudo-nitzschia spp. and the Cylindrotheca complex) at the more protected beaches from the northern and central areas. A third trend emerged because of the response of the phytoplankton to an extended, warmer summer period during the second annual cycle, when the presence of A. glacialis and A. australis was masked by the contribution of T. nitzschioides, Pseudo-nitzschia spp. and the Cylindrotheca complex. During short periods of time, and at the most protected beaches of the northern coast, the higher contribution of dinoflagellates was in agreement with Margalef's mandala: higher water column stability favours cells provided with a flagellum.