Influence of environmental factors on diatoms and dinoflagellates in Lake Tovel (Trentino, Italy)

摘要

Lake Tovel is an oligotrophic mountain lake (1177 m a.s.l.) located in the Brenta Dolomites (Central Alps). The lake has become famous since the beginning of the 20th century because of red blooms of the dinofla-gellate Glenodinium sanguineum Marchesoni. The reddening occurred in the small and shallow (max. depth = ca. 4.5 m) SW lake basin called "Red bay", usually during the central hours of the day between July and September (Baldi 1941, Marchesoni 1959). The phenomenon suddenly ceased after 1964. Since then, numerous investigations have been carried out at the lake to understand the red bloom dynamics (e.g. Paganelli 1992, Cantonati et al. 2003). The present investigation was conducted within the SALTO project (2001-2004) and represents the last contribution to these studies. The water regime of Lake Tovel has a very dynamic relationship with the morphology of its large calcareous catchment: retention time is very short after ice thaw (Paganelli 1992), and the lake level decreases beneath the outlet level during dry periods because of submerged outlets (Ferretti & Borsato, in press).