High Latitude Meiofaunal Macroecology and Diversity Assessed Using Both Morphological and Molecular Techniques
Instituto Antártico Chileno (INACh) Project T_13-10
Summary of the project
The meiofauna are an extremely important component of the marine benthos. Relatively little is currently known about the meiofauna and other small benthic metazoan fauna of the Antarctic (see Giere, 2009 for a review). Thus there is a barrier to further research as basic information concerning diversity and distributions is currently unavailable in the literature. This project is designed to survey the diversity of small metazoan fauna in the intertidal environments at a number of sites across the Magellanic and Antarctic regions using a morphological and molecular approaches. With this information, a number of macroecological and biogeographic hypotheses will be tested in order to identify some of the mechanisms that explain these patterns. This will be achieved by extensive quantitative and qualitative sampling of all intertidal micro-habitats encountered during the field work. Qualitative samples will be preserved in DESS a solution that allows the fauna to be examined and recorded using both traditional morphological methods and newer molecular methods (see Yoder et al., 2006). In addition, quantitative sediment samples will be fixed in 5% formalin to allow species abundance information to be collected. The initial focus will be on the phylums Nematoda and Tardigrada. Nematoda are one of the most abundant and diverse of all the marine faunas, ubiquitous throughout the marine benthic environment (Coomans, 2000; Eyualem-Abebe et al., 2008; Lambshead & Boucher, 2003). Tardigrades, though less diverse than Nematodes are also ubiquitous throughout the benthic marine environment. They are particularly important in the study of phylogenetics due to their uncertain position in the tree of life (Nelson, 2002). With future studie in mind, all material collected will be preserved providing an enormous source of material for taxonomic and diversity studies of all the groups typically found within the meiofauna. Proposed sampling sites are Isla Navarino, King George Island, Deception Island, Paradise Bay, and Adelaide Island (Rothera).
The few meiofaunal studies conducted in Antarctica so far have in general presented their information at higher taxonomic levels only (e.g. Bright et al., 2003; Gutzmann et al., 2004). However, Barnes et al. (2009b) suggest that with more intensive sampling of the intertidal zone the number of known meiobenthic taxa will increase, particularly the nematodes which have been greatly under-reported. Nematodes are typically the most abundant group within the meiofauna, they are also characterised by their high diversity and ubiquity (Heip et al., 1985). The current information concerning the diversity of nematodes in Antarctic waters is primarily confined to the deep-sea (e.g. Gutzmann et al., 2004; Ingels et al., 2006; Vermeeren et al., 2004), based on samples collected during the ANDEEP series of cruises. A search of the SCAR-MarBIN portal indicates that there are currently 385 species of nematodes described for the Antarctic region (RAMS, 2010). It is therefore likely that there are many more species yet to be described. Furthermore, the application of molecular techniques will undoubtedly reveal cryptic species complexes, as has been the case in other areas (Bhadury et al., 2008; Derycke et al., 2007, 2010). The generation DNA barcodes, for the most abundant species at least, will provide significant useful information that can be applied in further ecological studies of the habitat and future environmental impact assessments in the area. The knowledge of Antarctic marine tardigrade fauna is sofar limited to three publications (Bellido & Bertrand, 1981;Villora-Moreno, 1998; Miller & Kristensen, 1999) and an unpublished collection from a cruise studying the meiobenthos of the Southern Ocean (Petersen, 1990). This project to link collections of marine tardigrades from coastal South America to the coastal waters of the maritime Antarctic would be the first of its kind and would make a significant contribution to science.
Though the intertidal zone in Antarctica appears at first glance to be devoid of fauna, particularly in those areas subject ice-scour, a study by Waller (2008) indicated that there is a considerable diversity of fauna within cryptic intertidal habitats such as the undersides of boulders and protected interstices, at a number of sites across the region including Rothera our most southerly proposed sampling site. It is important to keep in mind that these sessile invertebrates form important micro-habitats that can be occupied by meiofauna. It is therefore likely that there remains a considerable amount of faunal diversity to be discovered in the benthic intertidal and shallow sublittoral habitats of Antarctica.
The connectivity between the faunas of the South American continent and Antarctica and the possible routes by which species could disperse between the two are discussed by Clarke et al. (2005) and Clarke (2008). However, with respect to meiofauna, the current situation is that there is insufficient to draw any general biogeographical conclusions. The standard macroecological theories predict that species diversity will decrease with increasing latitude. However as the number of taxonomic groups studied is increased the picture becomes less clear. For example in the case of marine invertebrates, whether the species diversity increases or decreases with increasing latitude appears to be predicted by the life-cycle of the group (Fernandez et al. 2009). In the case of the free-living littoral Nematoda an analysis of the data available in the literature (Lee, in prep.) indicates that diversity increases with increasing latitude along the Chilean coast of South America. Bergmann’s Rule predicts that species body size will increase with increasing latitude (Blackburn et al., 1999). It is well known that Antarctic marine invertebrates are often larger than their more northerly relatives. In the case of nematodes there is laboratory evidence that nematodes cultured at lower temperatures grow more slowly but achieve larger body sizes (Van Voorhies, 1996). However, when nematodes along the Chilean coast of South America are taken as a group there is a decline in average nematode body size with increasing latitude (Lee, unpublished data). Thus, an evaluation the diversity of Antarctic intertidal mieiofauna using both morphological and molecular techniques; the comparison between Magellanic and Antarctic meiofauna community and the testing of various macroecological hypotheses will be the important contributions of this research to Antarctic science.