Abstract
Despite recent advances in polar marine biology and related fields, many aspects of the ecological interactions that are crucial for the functioning of Antarctic shallow water habitats remain poorly understood. Although epiphytic diatoms play an essential role in the Antarctic marine food web, basic information regarding their ecology, biodiversity and biogeography is largely unavailable. Here, we synthesise studies on Ross Sea epiphytic diatoms collected during 11 summer Antarctic expeditions between the years 1989/90 and 2011/12, presenting a full list of diatom taxa associated with three macroalgal species (Iridaea cordata, Phyllophora antarctica, and Plocamium cartilagineum) and their epiphytic sessile fauna. Diatom communities found during the three summer months at various depths and sampling stations differed significantly in terms of species composition, growth form structure and abundances. Densities ranged from 21 to >8000 cells mm-2, and were significantly higher on the surface of epiphytic micro-fauna than on any of the macroalgal species examined. Generally, host organisms characterized by higher morphological heterogeneity (sessile microfauna, ramified Plocamium) supported richer diatom communities than those with more uniform surfaces (Iridaea). Differences between epiphytic communities associated with different macroalgae were reflected better in species composition than in growth form structure. The latter changed significantly with season, which was related strongly to the changing ice conditions. A general trend towards an increasing number of erect forms in deeper waters and tube-dwelling diatoms in the shallowest sites (2–5 m) was also observed. This study explores further important and largely previously unknown aspects of relationships and interactions between Antarctic epiphytic diatoms and their micro- and macro-environments.
Highlights
Macroalgae are an important element of the shallow-water ecosystems of the Ross Sea
We focus on epiphytic diatoms from Terra Nova Bay and Cape Evans (McMurdo Sound; Fig 1) examining material obtained during 11 summer Antarctic expeditions to these locations in the seasons 1989/90–2011/12
Cocconeis fasiolata, Fragilariopsis nana and Navicula perminuta occurred in all 46 samples (166 macroalgal replicates) analysed, and Achnanthes brevipes, A. vicentii, C. antiqua, F. curta, Melosira adeliae, Pseudogomphonema kamtschaticum and Synedropsis recta were present in more than 75% of the samples
Summary
They provide refuge and habitats for micro- and macrofaunal communities and comprise a large biomass They constitute a significant food source for Antarctic marine organisms, but with most of this flowing through detritus-based food chains [1, 2, 3, 4, 5]. By this means, mineral nutrients are released into the water and sediments and can be assimilated by aquatic primary producers and incorporated again into the trophic system [6, 7]. Epiphytic diatom communities clearly must play a important role in the functioning of Antarctic shallow water ecosystems, many aspects of their ecology, taxonomy, distribution and biodiversity remain understudied and poorly understood
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