Regulation of planktonic ciliate dynamics and functional composition during spring in Lake Constance

Abstract

Protozoans are among the most important grazers of phytoplankton and remineralizers of nutrients in marine and freshwater ecosystems, but less is known about the regulation of their population dynamics. We analyzed a 12 yr data set of ciliate biomass and species composition in large, deep Lake Constance to understand the factors influencing ciliate spring development. The start of ciliate net growth in spring was closely linked to that of edible algae, chlorophyll a and the vertical mixing intensity, but independent of water temperature. During ciliate spring growth, the relative contribution of ciliated interception feeders was positively related to that of cryptomonads, whereas the relative contribution of filter feeders correlated positively with that of non-cryptomonads. The duration of ciliate dominance in spring was largely controlled by the highly variable onset of the phytoplankton bloom, as the termination of the ciliate bloom was less variable. During years with an extended spring bloom of algae and ciliates, internally forced species shifts were observed in both communities. Interception feeders alternated with filter feeders in their relative importance as did cryptomonads and non-cryptomonads. Extended spring blooms were observed when vertical mixing intensity was low at low temperatures during early spring, which will become less likely under the anticipated climate change scenarios. The termination of the ciliate spring bloom occurred prior to a reduction in food concentration and mostly also prior to the mass development of daphnids alone, but coincided with increased grazing by various predators together, such as rotifers, copepods and daphnids in late May/early June.

Warming induces shifts in microzooplankton phenology and reduces time-lags between phytoplankton and protozoan production

“…Next to temperature, the factor light might alter the timing and biomass of phytoplankton and microzooplankton, since, for example, higher light intensities were shown to increase peak biomass of primary producers thus enhancing consumers' production due to enhanced food availability (Diehl et al 2002;Tirok and Gaedke 2007). In our study, neither the timing nor the peak magnitudes of microzooplankton were affected by light, a pattern which was most likely related to the rather narrow range of light intensities applied.…”

Individual Cell Based Traits Obtained by Scanning Flow-Cytometry Show Selection by Biotic and Abiotic Environmental Factors during a Phytoplankton Spring Bloom

“…The original PEG model suggests that the main drivers of spring phytoplankton communities are physics (responding to the weather), grazing, and water chemistry [23]. Ciliates are the first herbivores appearing in spring and the first to graze on the phytoplankton community, and their important role in spring-bloom dynamics has become increasingly recognized [22], [46], [47]. Our data suggest ciliates were the main grazers of the phytoplankton community during the early spring-bloom, and were followed by multicellular larger zooplankton species [46], [47] (Copepods and Cladocera) that may have played a role as grazers after the ciliate bloom was over (Fig.…”

The response of temperate aquatic ecosystems to global warming: novel insights from a multidisciplinary project

“…Similarly, detailed field studies suggest the presence of highly efficient life cycles strategies in a freshwater copepod to tackle the phenology of its food source, that is, the phytoplankton spring bloom (Seebens et al 2009). In the case of the phytoplankton-heterotrophic protist link, warming increased the temporal synchrony between both trophic levels as well Tirok and Gaedke 2007a).…”