Epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica)

In polar waters, microalgal communities associated with macroalgae exhibit rates of primary production comparable or even higher than those of phytoplanktonic ones. These benthic communities are mainly represented by diatoms. Despite to their crucial ecological role, the biodiversity of Antarctic epiphytic diatoms is poorly studied and greatly underestimated. In the present study, the diversity of epiphytic diatom communities from coastal waters of Terra Nova Bay was investigated and described for the first time. Samplings were made during the 8 Italian Antarctic expeditions in the space of 15 years. Thalli of Iridaea cordata, Phyllophora antarctica and Plocamium cartilagineum were collected during the austral summer. Collections were made from different depths at 5 sampling sites. Taxonomical identification and counting of diatom cells has been carried out by scanning electron microscope. According to our results biomass appears to be inversely related to the diversity. The diatom community composition varied depending on the sampling site as well as on the morphology of the macroalgal host. Some differences could be observed along a depth gradient. In terms of growth form in most cases adnate (e.g. Cocconeis, Amphora) and mobile forms (e.g. Navicula, Nitzschia) dominated. Erect diatom taxa tended to be associated with animal macrofouling species.