Biological and environmental characterization of marine macroalgal assemblages in Potter Cove, South Shetland Islands, Antarctica

We describe the macroalgal assemblages in Potter Cove and their distribution by depth, substratum, irradiation, nutrients, salinity, water temperature and light period. We determined groups by using K-means, the Hellinger index and the maximum Calinski-Harabasz pseudo-F-statistic as stopping rule. Indicator species were assessed with the IndVal index. Relationships between groups and environmental factors were determined by correspondence analysis, and results were validated by a canonical correspondence analysis of species and environment. To compare the group biodiversities we used species richness and diversity indices and abundance biomass comparisons curves. Analysis with incidence data discriminated one shallow Iridaea assemblage and one deep Himantothallus assemblage. Analysis using biomass discriminated three facies, the first in the upper zone (Iridaea cordata, Monostroma hariotii, Adenocystis utricularis, Enteromorpha bulbosa), the second (Desmarestia menziesii, D. antarctica, Ascoseira mirabilis, Curdiea racovitzae, Gigartina skottsbergii, Kallymenia antarctica, Neuroglossum delesseriae, Phaeurus antarcticus, Gymnogongrus turquetil) at intermediate depth and the third (H. grandifolius, D. anceps, Georgiella confluens, Ballia callitricha, Plocamium cartilagineum), coincident with the deep qualitative assemblage, was found in a less disturbed environment. The difference in species composition between the groups was mainly related to depth as an environmental variable. The high specific diversity at intermediate depths can be explained by the presence of patches in different successional stages caused by iceberg scouring.