Spatial and temporal variation of benthic marine algae at the Cabo Frio upwelling region, Rio de Janeiro, Brazil

Abstract

The Cabo Frio (23°01′S, 42°00′W) upwelling region has been recognized as a biogeographic barrier to the macroalgal flora of the Brazilian coast. Five sites in this area were studied to evaluate the regional variation (along an upwelling gradient) and local variation of the flora (under similar upwelling influence); collections were also made in different seasons of the year from November 1988 to April 1990 to document temporal variation. Some variables (temperature, salinity, total inorganic nitrogen and total phosphate) were analyzed to determine the oceanographic characteristics influencing the studied sites. Hierarchical Cluster Analysis and Ordination Factorial Analysis of Correspondence (FAC) were used to determine the structure of the macroalgae community in this area. The sites influenced by the upwelling waters showed lower water temperature values and higher nutrient concentrations in the spring-summer upwelling period. The benthic flora survey recorded elements with warm temperate affinities (i.e. Ceramium diaphanum (Lightfoot) Roth, Polysiphonia decussata Hollenberg and Endarachne binghamiae J. Agardh) and algae with tropical affinities (i.e. Gelidiopsis gracilis (Kützing) Vickers, Dictyota cervicornis Kützing and Caulerpa racemosa (Forsskål) J. Agardh). In general the local flora showed a peak in reproduction during the spring-summer period. The multivariate analysis distinguished the sites influenced by upwelling waters, and some samples taken in the same inlet suggested that further differences in the floral composition were due to wave exposure.