Seasonal dynamics and annual production of Cystoseira crinita (Fucales: Ochrophyta)-dominated assemblages from the northwestern Mediterranean

Abstract

Algae of the genus Cystoseira are the main engineering species on Mediterranean shallow rocky bottoms. Cystoseira crinita is an endemic species which grows in shallow and rather sheltered environments throughout the entire Mediterranean Sea. In order to investigate its role in structuring benthic assemblages and as a primary producer, three localities were sampled every two months during one year in Menorca (Balearic Islands). The total biomass of Cystoseira crinita-dominated assemblages showed a seasonal pattern mainly due to temporal changes in the biomass of the dominant alga. The assemblages also showed seasonality in their species richness (number of species per sample). Both total biomass and species richness peaked in summer, and their lowest values were recorded in winter. Despite these temporal patterns, C. crinita-dominated assemblages from Menorca showed reduced seasonality compared to C. crinita-dominated assemblages in other areas in the western Mediterranean, as C. crinita specimens kept their branches throughout the entire year. Total annual production of Cystoseira crinita branches and cauloids was around 1230 g dwt m–2, which is higher than that of other Cystoseira species living in sheltered areas but much lower than that of Cystoseira species growing on exposed shores. Production was highly seasonal, and was highest in spring and null in winter and late summer.