Marine benthic communities of the Magellan region, southern Chile: Contributions of different habitats to the overall biodiversity

Abstract

The community structure in three habitats characterizing the heterogeneous conditions of the Magellan waters was studied. Structural parameters such as abundance, biomass,species richness and composition, dominance, diversity and evenness were considered in the investigation. Two of the habitats - intertidal boulder and cobble terraces and sublittoral soft-bottom areas - derive directly from the glacier processes affecting the region as a whole. The third one is a specific biogenic habitat provided by the holdfasts of the kelp Macrocystis pyrifera. A total of 66 macrofaunal species and higher taxa were sampled in the intertidal habitat, representing the benthic community with the lowest species number, density and biomass.The sublittoral soft bottoms were studied in the eastern Straits of Magellan, the central and western Straits and off the South Patagonian Icefield (SPI). A total of 301 macrobenthic species and higher taxa were obtained from six periods of quantitative sampling in the Segunda Angostura. Again low sample species richness, relatively low abundances and strong dominance of few species were found. Species richness was about the same in the two discriminated areas, but the abundances in the channels were consistently higher thanin the SPI area influenced by glaciers. The kelp (Macrocystis pyrifera) forests provideanother characteristic habitat in the Magellan region. Only the holdfast associated organisms from two kelp forests were considered in this thesis, with a total of 114 speciesand higher taxa identified. The results showed a distinct dominance of few species and a high species turnover within and between sites.Local densities, species composition and species richness differed greatly within and among study habitats. Patterns in community structure were found, especially changes with depth in species richness, abundance and biomass, however without any latitudinal trend along the Magellan region. For all the studied habitats the species richness at samplescale was found to be rather low (low 1 diversity) and with a high turnover of species, resulting in an increased regional diversity.The Magellan region was found to be considerably richer than the northern hemisphere seas, most likely due to lower disturbance by anthropogenic factors.