Salinity, depth and the structure and composition of microbial mats in continental Antarctic lakes

• Published in: Freshwater Biology
• Main Authors: Sabbe, Koen, Hodgson, Dominic A., Verleyen, Elie, Taton, Arnaud, Wilmotte, Annick, Vanhoutte, Koenraad, Vyverman, Wim
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Blackwell 2004
• Subjects: Biology and Microbiology; Ecology and Environment; Antarctic; East Antarctica; Larsemann Hills; Bolingen Islands; Antarc*; Antarctica
• Online Access: http://nora.nerc.ac.uk/id/eprint/12406/; http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2427.2004.01186.x/full

1. Lakes and ponds in the Larsemann Hills and Bolingen Islands (East-Antarctica) were characterised by cyanobacteria-dominated, benthic microbial mats. A 56-lake dataset representing the limnological diversity among the more than 150 lakes and ponds in the region was developed to identify and quantify the abiotic conditions associated with cyanobacterial and diatom communities. 2. Limnological diversity in the lakes of the Larsemann Hills and Bolingen Islands was associated primarily with conductivity and conductivity-related variables (concentrations of major ions and alkalinity), and variation in lake morphometry (depth, catchment and lake area). Low concentrations of pigments, phosphate, nitrogen, DOC and TOC in the water column of most lakes suggest extremely low water column productivity and hence high water clarity, and may thus contribute to the ecological success of benthic microbial mats in this region. 3. Benthic communities consisted of prostrate and sometimes finely laminated mats, flake mats, epilithic and interstitial microbial mats. Mat physiognomy and carotenoid/chlorophyll ratios were strongly related to lake depth, but not to conductivity. 4. Morphological-taxonomic analyses revealed the presence of 26 diatom morphospecies and 33 cyanobacterial morphotypes. Mats of shallow lakes (interstitial and flake mats) and those of deeper lakes (prostrate mats) were characterised by different dominant cyanobacterial morphotypes. No relationship was found between the distribution of these morphotypes and conductivity. In contrast, variation in diatom species composition was strongly related to both lake depth and conductivity. Shallow ponds were mainly characterised by aerial diatoms (e.g. Diadesmis cf. perpusilla and Hantzschia spp.). In deep lakes, communities were dominated by Psammothidium abundans and Stauroforma inermis. Lakes with conductivities higher than +/-1.5 mS cm(-1) became susceptible to freezing out of salts and hence pronounced conductivity fluctuations. In these lakes P. abundans and S. ...