Winter conditions in six European shallow lakes: a comparative synopsis

Abstract

Abstract. This review summarizes winter conditions from six polymictic European shallow lakes. The lakes range from oligotrophic to hyper-eutrophic. Four of the lakes freeze regularly while ice cover is absent or rare in the two others. Ice duration and timing of ice-out are significantly influenced by climate signals in three of the lakes. Winter water temperature remains higher in nonice-covered lakes. No long-term trend in temperature is detectable except for one lake where winter water temperature began to increase in 1986. Secchi depth in winter is equal or greater than summer values in all six lakes indicating relatively better light conditions in winter. Total phosphorus concentration in winter ranges from 10 to 130 µg L -1 , which is equal or lower than summer values and is unrelated to chlorophyll a in five of the sites. Phytoplankton species composition during winter differs largely at the six sites. The winter assemblages largely depend on the trophic level and the conditions during the previous season. Winter chlorophyll a and phytoplankton biomass are usually lower than summer values because of reduced photosynthetic rates. Bacterial production often exceeds primary production. Epipelic algal assemblages tend to proliferate during winter in both ice-covered and non-ice-covered lakes. Primary production is low during winter because of insufficient light. Zooplankton abundances and biomass critically depend on conditions during the previous season and the winter situation and are quite variable from year to year, but their values correlate with the trophic status of the lakes. As a result, winter conditions are important to understand seasonal and annual changes in shallow lakes.

The role and composition of winter picoeukaryotic assemblages in shallow Central European great lakes

“…High 553 cellular chlorophyll a content of the phytoplankton biomass is also a result of low-light 554 acclimation of the winter assemblage. In Lake Balaton, the chlorophyll a content of the 555 phytoplankton biomass varies between 0.3 and 0.5% from spring to autumn, but increased to 556 1.5-2% in winter, when active movement or a high surface area is assumed to be 557 advantageous (Dokulil et al, 2014). This was also reflected in the phytoplankton composition 558 of the studied lakes with cryptophytes and Monoraphidium sp.…”

“…However, the observed I k values were much lower than 549 usual during the autumn to spring period in temperate shallow lakes (Dokulil et al, 2014; 550 Somogyi and Vörös, 2006;Vörös et al, 1991). Low I k is characteristic of phytoplankton 551 adapted to low light, which is capable of developing maximal photosynthetic rate at low mean 552 irradiance and has accessory photosynthetic pigments (Darchambeau et al, 2014).…”

Ecology under lake ice

“…Although zooplankton biomass generally appears to be lower under ice, changes in community composition can be highly variable across lakes (Dokulil et al . ). Even more scarce is information about nutrient and dissolved organic carbon concentrations under the ice that may help to drive many of these plankton dynamics (but see Özkundakci et al .…”

“…Such carry‐over between seasons is not restricted to winter's influence on summer, of course, and there is evidence that under‐ice zooplankton dynamics can depend in part on late summer zooplankton biomass (Dokulil et al . ). The diversity of responses found by under‐ice studies suggests that a synthesis of existing knowledge is greatly needed and would help identify key next steps in winter limnology as well as promote productive collaborations (Hampton et al .…”

Environmental Impacts of Tourism on Lakes

“…The littoral zone and the aquatic vegetation are usually more significant for shallow ecosystems. These and other factors are summarized in Dokulil et al (2012).…”