Limnological Characteristics of Inland, Glacial Lakes on the Horseshoe Island (Antarctica)

Antarctica is a continent with extreme climatic conditions, with many lakes and ponds with ecological status varying from ultra-oligotrophic to hypereutrophic. Horseshoe Island is situated in Marguerite Bay, in the western Antarctic Peninsula. In this research, we purpose to determine the limnological characteristics of four lakes on Horseshoe Island (Col 1, Col 2, Skua and Zano). Water samples were taken once (during the summer period) from one station in each of the lakes for chemical analysis. The Trophic State Index (TSI) was calculated based on Secchi depth, chlorophyll-a, and total phosphorus concentrations. Phytoplankton were sampled from the same stations, except for Lake Zano, because of the ice cover. Phytoplankton community indice (Q) was calculated. Total phosphorus concentration for Lake Col 1, Col 2, Skua and Zano were measured as 0.6, 0.65, 3.0, 4.6 mg/m3, respectively. Based on total phosphorus, these four lentic systems are oligotrophic. TSI values pointed out oligotrophy and mesotrophy in the lakes. Lake Skua was found to be excellent quality (0.59 mg/l) while Lake Col 1 (0.72 mg/l) and Lake Col 2 (0.68 mg/l) were found to be good quality according to total phytoplankton biomass. The ecological status of the lakes is prediction to be of medium quality based on cyanobacteria biomass. This may be due to the rapid increase of Cyanobacteria in the short summer period as well as nutrient enrichment. Based on the Q indice, Lake Skua (4.2) is of excellent quality, Lake Col 2 (4) is of good quality, and Lake Col 1 (2.73) is of moderate quality in ice-free period. Because these lakes are under stressors such as climatic pressure (duration of ice cover) and natural eutrophication processes, regular monitoring of the lakes on the Antarctic continent is recommended.