Blooms of the dinoflagellate Glenodinium sanguineum obtained during enclosure experiments in Lake Tovel (N. Italy)

Abstract

Freshwater red tides due to dinoflagellates are less common than their marine analogues, which are usually a serious problem and can even be toxic. This was not the case for Lake Tovel in the Adamello-Brenta Natural Park (Southern Alps, Italy), where the dinoflagellate Glenodinium sanguineum Marchesoni accumulated carotenoids (astaxanthin-like compound) and caused a spectacular and regular "summer reddening", which suddenly ceased in 1964. Today Lake Tovel is a temperate, meromictic (with dimictic mixolimnion), oligotrophic mountain lake, characterised by marked water level fluctuations. G. sanguineum is still present in the lake, although with markedly lower densities in comparison to the pre-1965 period. Enclosure studies were carried out to identify the main factors regulating the blooms. In 1998, by means of phosphorus enrichments, it was possible to obtain a marked increase in numbers of G. sanguineum. Phosphorus additions in similar enclosures in 1999, when weather conditions during the summer were not optimal (mostly cloudy with frequent rainfalls), did not have the same effect, since species known to thrive in spring or under icecover developed. In summer 2000, by attenuating light in one of the enclosures, it was shown that irradiance conditions strongly interacted with phosphorus availability in determining the species that dominated the phytoplankton. In summer 2001, G. sanguineum increased again in the enclosure enriched with phosphorus. Nitrogen was observed to become a limiting factor only in conditions forced by phosphorus additions. From the first four years of in situ experiments, we concluded that phosphorus and light conditions were among the key factors controlling the proliferation and the dominance of G. sanguineum

Morphological differences and molecular phylogeny of freshwater blooming species, Peridiniopsis spp. (Dinophyceae) from China

“…Dinoflagellate blooms usually occur in both nutrient-rich marine and freshwater environments (Cantonati et al 2003). Due to dinoflagellates, the blooms are much less widespread in freshwater than in the sea and mainly caused by Ceratium hirundinella (O.F.…”

The Effects of Temperature, Nitrogen, and Phosphorus on the Encystment of Peridinium cinctum, Stein (Dinophyta)

“…Factors controlling encystment and excystment were shown to be crucial in understanding the development and decline of cyanobacterial blooms (Karlsson, 1999(Karlsson, , 2003Karlsson-Elfgren et al, 2003;Moore et al, 2003). Recently, many aspects of dinoflagellate blooms, such as timing, location, and duration, have been linked to the encystment or excystment cycle both in small and large lakes (Flaim et al, 2003(Flaim et al, , 2004Cantonati et al, 2003). Prediction of phytoplankton blooms by setting up ecological models also needs a sufficiently detailed knowledge of the ecology of resting stages (Huppert et al, 2002).…”

Weather-driven ecology of planktonic diatoms in Lake Tovel (Trentino, Italy)

“…After the red blooms suddenly ceased in 1964 several investigations were carried out to understand reasons responsible for the bloom disappearance (e.g. Vittori, 1969;Gerosa, 1970;Dodge et al, 1987;Paganelli, 1992;Corradini et al, 2001;Cantonati et al, 2003).…”