Webpages tagged with «Limnology»
Hydrurus foetidus (Vill.) Trev. is one of the few macroscopic freshwater golden algae (Class Chrysophyceae) - and, contrary to most other sessile freshwater algae, it prefers winter conditions in rivers and brooks where temperature is near to 0° C. During the first months of spring, it may bloom and cover the bottom where turbulence is high and light conditions are best. At Finse, the Garpefoss out of lake Finsevatn is a locus classicus - studied by Strøm for his doctoral dissertation (see Strøm 1926), and where Hydrurus still occurs regularly from end of February through the spring months.
Surviving the winter is a special challenge for herbivorous aquatic invertebrates in the alpine region due to long period of ice cover and cessation of primary production. Daphnids that reproduce parthenogenetically during the summer, with 2-3 generation through July and August, solve that problem with depositing sexually produced resting eggs in the autumn. However, the species at Finse, Daphnia umbra, also has an alternative strategy. Instead of producing parthenogenetic or sexual eggs in the autumn, they start storing lipid droplets in the body cavity.
Pyrosequencing is applied for the study of plankton and protist diversity in lake Finsevatn. This lake has been influenced by human activity, particularly since the tourism came to this high-mountain location with the opening of the Oslo-Bergen railway in 1909. Scientific investigations since 1986 have revealed the diversity of the lake's phytoplankton by microscopy, but new technology supplies a much more diverse picture involving microbial parasites and previously unknown protists - some with relatives in marine environments - see Bråte et al. (2010), Shalchian-Tabrizi et al. (2011).
Here we look at life-history adaptation in the arctic charr in a high mountain environment with a particular emphazis on its life history strategies. As this is a marginal environment with regard to the number and variability of degree-days (i.e. the temperature sum), and the length and variability of the feeding season, the charr must trade-off energetic requirements to growth and gonad allocation, and potentially adopt a bet-hedging strategy. Thus, alternative life-history strategies may evolve in such harsh environments as compared to the founder population which exists in a very divergent lowland environment.
Lake Flakavatn, 6 km north-northeast of Finse, was visited by the limnologist Kaare M. Strøm in August 1933. He did a geomorphological survey of the watershed, he made a bathygraphical map of the lake, and he recorded some basic limnological observations which are the foundation of our continuing work in this lake. The present project in lake Flakavatn is part of a long-term program covering lakes with similar limnological properties but located under different climatic conditions within Norway - "The Limnology of Ultraoligotrophic Lakes". Students, post-docs and colleagues from various disciplines are taking part in the Flakavatn project - emerging and experienced scientists from all subdusciplines are welcome!