Download Effect of chrysophytes on lake secondary production (ChrysoLake)

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Effect of chrysophytes on lake secondary production
(ChrysoLake)
Summary
Global change is expected to have far reaching consequences on hydrological processes at
the catchment level. For lakes in the temperate zone, it is expected to enhance the intensity
and duration of thermal stratification, as well as the input of allochthonous carbon from the
catchment into the lakes (‘brownification’). While changes in the plankton of eutrophic lakes
(e.g. a proposed dominance of cyanobacteria) are a widely discussed topic in the current
literature, the consequences of global change for oligotrophic lakes receive little attention.
Mixotrophic chrysophytes are a prevailing element of phytoplankton in oligo- and
mesotrophic lakes. Their contribution is predicted to increase with global change-associated
phenomena (brownification and enhanced thermal stratification). There is indication for
detrimental effects of chrysophytes on zooplankton growth and reproduction, which implies
serious consequences for pelagic trophic efficiency and ecosystem services e.g. fish
production. However, our current understanding on the bottom-up effect of chrysophytes
on secondary production is fragmentary.
I propose to study the effects of chrysophytes on zooplankton secondary production and
community composition. Laboratory feeding experiments will be combined with field
observations to quantify species-specific responses of relevant zooplankton taxa to
chrysophytes. The underlying mechanisms will be explored by biochemical analyses of algae
and consumers. The proposed research joins several state-of-the-art methods (biochemical
lipid and RNA:DNA ratio analyses, traitbased approach) to get a comprehensive
understanding on the role of this key group for the functioning of lake ecosystem.
Many nutrient-poor lakes (particularly in alpine and northern regions) have highly valuable
fish stocks (salmonids) and they represent important recreational sites. Altering zooplankton
composition and productivity may contribute to changes in fish community, with serious
imprint on ecosystem services. Besides, crysophyte blooms can cause unpleasant fishy
odour.
My study will be a first step to specifically address the consequences of mixotrophic algae
for secondary production in freshwater. Therefore, the proposed research is at the forefront
of contemporary research in the context of global change and lake food webs, and will
stimulate followup projects. It will significantly contribute to the understanding of carbon
flow and nutrient cycling in alpine lakes under global change.