Biodiversity seasonal patterns of marine benthic habitats of the Portuguese coast

Abstract

The intertidal zone of the temperate Portuguese coasts is a species rich habitat with complex communities, which is a product of a convergence of physical factors - such as the effect of waves and tides - and biological- interactions between individuals and between individuals and environment - that make these intertidal communities a characteristic ecosystem of great ecological value and of scientific interest. The present study aims to study the seasonal variations of biodiversity in two different areas located in the beach of Cabo Raso, in Cascais (Portugal). These are: Cabo Raso 1 and Cabo Raso 2 (figure 1). For this purpose, samples of a transept of thirteen meters were collected on both places and a counting, measurement and identification of the individuals and algae present in the samples was done. Based on the data obtained, the diversity indexes of Margalef, Pielou, Fisher, Brillouin, Shannon-Wiener, Simpson, Hill and rarefaction index were calculated along with species richness and number of individuals using PRIMER 6 software. The relative abundances of the species of individuals in each season of the year and in each area were also calculated in order to determine the most abundant species of macroinvertebrates and algae. The results of the indexes showed seasonal diversity patterns in both areas, with maximum biodiversity in summer for Cabo Raso 1 and 2 and minimum biodiversity during autumn and spring on the area of Cabo Raso 1 and Cabo Raso 2 respectively. Biodiversity values were higher in Cabo Raso 1. The dominant macroinvertebrate species at Cabo Raso 1 were Mytilus galloprovincialis, Rissoidae sp. Fabricia sterallis and M. galloprovincialis in autumn, winter, spring and summer, respectively. Corallina elongate was shown as the most abundant species of algae in Cabo Raso 1. At Cabo Raso 2, Melarphaphe neritoides, M. galloprovincialis, Cthamallus sp. and Chironomidae were found as major species in the seasons of autumn, winter, spring and summer respectively. The majority species of macroalgae in Cabo Raso 2 were Fucus spiralis in autumn and winter, Codium sp during spring and Corallina elongata in summer. The realization of this study acknowledge the seasonal diversity of two characteristic areas within a characteristic beach of the intertidal zone, in parallel with the characterization of the community of macroinvertebrates and algae during the four seasons