Comparative seasonal and spatial distribution of decapod larvae assemblages in three coastal zones off the south-western Iberian Peninsula

Abstract

Plankton studies over the long southern coast of Iberian Peninsula are very scarce and restricted to a few specific taxonomic groups. In order to know the dynamic of decapod larvae coastal assemblages from south-western of Iberian Peninsula, three zones were studied: Guadalquivir Estuary, Cádiz Bay and Algeciras Bay. The three zones differ by their freshwater inflow and turbidity (highest in Guadalquivir Estuary), primary production (highest in Cádiz Bay) and nutrient concentrations (lowest in Algeciras Bay). The material is based upon plankton samples (250 μm mesh) collected monthly at eight stations distributed between these zones, during 1 year. Maximum values of abundance and diversity were found in Cádiz Bay, while the lowest were recorded in Algeciras Bay. Brachyura was the main abundant taxonomic group in larval decapod assemblages, while Dendrobranchiata, Palinura, Stenopodidea, and Astacidea were scarcely represented or absent. From the 69 taxa identified, 11 were considered rare and 12 taxa constituted 87% of the total larvae collected. Liocarcinus spp. was the most representative taxon, being present in all stations and showing high abundance and dominance values. The annual distribution was specifically studied for Liocarcinus spp., Carcinus maenas, Xantho spp., Ilia nucleus, Uca tangeri, Brachynotus spp., Hippolyte spp., Philocheras spp., Pisidia longicornis, Diogenes pugilator, Pilumnus spp. and Upogebia sp. Attending to the temporal distribution of dominant taxa, three abundance patterns are shown for decapod larvae at study zones: (i) species present in non-warm months; (ii) species present in warm months; (iii) species present through all year.