Limnology and aquatic microbial ecology of byers Peninsula: A main freshwater biodiversity hotspot in Maritime Antarctica

Abstract

Here we present a comprehensive review of the diversity revealed by research in limnology and microbial ecology conducted in Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica) during the last two decades. The site constitutes one of the largest ice-free areas within the Antarctic Peninsula region. Since it has a high level of environmental protection, it is less human-impacted compared to other sites within the South Shetland archipelago. The main investigations in Byers Peninsula focused on the physical and chemical limnology of the lakes, ponds, rivers, and wetlands, as well as on the structure of their planktonic and benthic microbial communities, and on the functional ecology of the microbial food webs. Lakes and ponds in Byers range along a productivity gradient that extends from the less productive lakes located upland to the eutrophic coastal lakes. Their planktonic assemblages include viruses, bacteria, a metabolically diverse community of protists (i.e., autotrophs, heterotrophs, and mixotrophs), and a few metazooplankton species. Most of the studies conducted in the site demonstrate the strong influence of the physical environment (i.e., temperature, availability of light, and water) and nutrient availability in structuring these microbial communities. However, top-down biotic processes may occur in summer, when predation by zooplankton can exert a strong influence on the abundance of protists, including flagellates and ciliated protozoa. As a consequence, bacterioplankton could be partly released from the grazing pressure exerted by these protists, and proliferates fueled by external nutrient subsidies from the lake's catchment. As summer temperatures in this region are slightly above the melting point of water, biotic processes, such as those related to the productivity of lakes during ice-free periods, could become even more relevant as warming induced by climate change progresses. The limnological research carried out at the site proves that Byers Peninsula deserves special attention in the framework of the research in extreme environments. Together with nearby sites, such as Signy Island, Byers Peninsula comprises a featuring element of the Maritime Antarctic region that represents a benchmark area relative to the global distribution and diversity of aquatic microorganisms.