Epiphytic diatom communities of Terra Nova Bay, Ross Sea, Antarctica: structural analysis and relations to algal host

Abstract

AbstractEpiphytic diatoms are important constituents of the Southern Ocean coastal water ecosystem, being a key element in many of the Antarctic trophic chains. However, only limited information exists relating to these microalgal communities. Here we describe our findings of a study on epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica) based on material collected during the summer campaigns spanning from 1990–2004. Observations of diatoms associated with three rhodophyte species (Iridaea cordata (Turner) Bory, Phyllophora antarctica Gepp & Gepp, and Plocamium cartilagineum (L.) Dixon) were carried out with the use of a scanning electron microscope. A total of 73 diatom taxa (32 genera) were distinguished, of which 20 taxa exceeded 3% of total abundance. Cocconeis fasciolata (Ehrenberg) Brown, Navicula perminuta Grunow, and Fragilariopsis nana (Steemann Nielsen) Paasche appeared in every sample. The analysis of similarities (ANOSIM) test as well as non-metric multidimensional scaling analysis indicated the nature of host organism as a major factor influencing associated diatom community structure, whereas depth, site, and time of sampling seemed to be less important. The epizooic communities associated with sessile fauna epiphytic on macroalgae differed significantly from those associated with macroalgal surface. A pronounced difference between the communities epiphytic on various host macroalgae species was also observed, although most of the dissimilarities occurred between diatom taxa of the same growth form.