A five-year study of autotrophic winter picoplankton in Lake Balaton, Hungary

Abstract

Picoeukaryotes dominate the phytoplankton of Lake Balaton-the largest shallow lake in Central Europe-in the winter period. We examined the annual dynamics of picoplankton abundance and composition in the lake in order to establish if the picoeukaryotes merely survive the harsher winter conditions or they are able to grow in the ice-covered lake when the entire phytoplankton is limited by low light and temperature. Lake Balaton has an annual temperature range of 1-29°C, and it is usually frozen between December and February for 30-60 days. In the spring-autumn period phycocyanin and phycoerythrin rich Cyanobacteria are the dominant picoplankters, and picoeukaryotes are negligible. Our five-year study shows the presence of three types of picophytoplankton assemblages in Lake Balaton: (1) Phycoerythrin-rich Cyanobacteria-the dominant summer picoplankters in the mesotrophic lake area;(2) Phycocyanin-rich Cyanobacteria-the most abundant summer picoplankters in the eutrophic lake area and; (3) Picoeukaryotes-the dominant winter picoplankters in the whole lake. The observed winter abundance of picoeukaryotes was high (up to 3 9 10 5 cells ml -1 ), their highest biomass (520 lg l -1 ) exceeded the maximum summer biomass of picocyanobacteria (500 lg l -1 ). Our results indicate that the winter predominance of picoeukaryotes is a regular phenomenon in Lake Balaton, irrespective of the absence or presence of the ice cover. Picoeukaryotes are able to grow at as low as 1-2°C water temperature, while the total phytoplankton biomass show the lowest annual values in the winter period. In agreement with earlier findings, the contribution of picocyanobacteria to the total phytoplankton biomass in Lake Balaton is inversely related to the total phytoplankton biomass, whereas no such relationship was observable in the case of picoeukaryotes.

Local environment overrides regional climate influence on regime shift in a north temperate lake

“…However, the positive trend between the small cellsized colonial cyanobacteria and maximum water temperature indicates a potential climate warming effect. This observation is strengthened by several studies showing that small-sized colonial cyanobacteria abundances were positively correlated with water temperature (Daufresne et al 2009;Vörös et al 2009). …”

“…Nutrient enrichment has been suggested as the major factor behind such invasions (Paerl and Fulton 2006), and accordingly, we here show that Lyngbya is losing its dominant position as water becomes clearer and less enriched in nutrients. The small-sized colonial cyanobacteria tended to dominate the cyanophyta and expressed a positive trend similar to the long-term variability in maximum water temperature, suggesting that warming may be a factor facilitating small-sized cyanobacteria (Vörös et al 2009). …”

Winter conditions in six European shallow lakes: a comparative synopsis

“…Ice duration and timing of ice-out are influenced by long-distance climate signals in Neusiedler See, Balaton, and in several Polish shallow lakes (Skowron, 2008;Dokulil and Herzig, 2009;Vörös et al, 2009). From these observations, a decline in ice duration at a rate of about 0.5 days per year can be deduced for these lakes.…”

“…Vertical attenuation coefficients under the ice (0.4-1.3 m -1 ) indicate relatively better light conditions compared to the summer situation both in Lake Balaton and Neusiedler See (Dokulil, 1979;Vörös et al, 2009). In both cases, improvement is due to the sedimentation of inorganic particles under the ice cover.…”

Ring-shaped bifocal lens used for fluorescent self-referenced holographic imaging

“…The realization of such an instrument would result in an immediate industrial benefit, for example, real-time water monitoring systems [1] can be built, where the use of self-referenced holography [2,3] is undoubtedly very profitable.…”