CHRYSOWEB · The effect of mixotrophic chrysophytes on secondary productivity in pelagic food webs

The effect of mixotrophic chrysophytes on secondary productivity in pelagic food webs

Plankton occupy a key position in aquatic trophic webs, therefore, understanding its global change-mediated shifts is of high importance. While changes in the plankton of eutrophic lakes (e.g. increased dominance of cyanobacteria) are a widely discussed topic in the current literature, the consequences of global change for oligotrophic lakes receives little attention. Mixotrophic chrysophytes (golden algae – Chrysophyceae) are important elements of the phytoplankton in lakes with a low nutrient content, such as alpine lakes. Their contribution is predicted to increase with global change-associated phenomena, such as enhanced thermal stratification and increased input of terrestrial carbon (‘brownification’). Though interactions between chrysophytes and zooplankton have hitherto received little attention, some studies clearly indicated detrimental dietary effects. According to this, an increase in chrysophytes could impair secondary production with far-reaching consequences for the whole ecosystem, including changes in the fish stock. Alpine lakes represent multiple ecosystem services. Salmonid fish populations of many mountain lakes are economically important. If golden algae impair zooplankton composition and production, their increase may imply changes in the fish stock. Besides, chrysophyte blooms can cause unpleasant fishy odour, decreasing the recreational value of their habitats. The aim of CHRYSOWEB was to specifically address the consequences of the increasing share of golden algae for consumers in lake food webs. To this end, we applied an integrative approach (laboratory experiments, field observations, biochemical analyses) to get a comprehensive understanding of this key group on aquatic ecosystem functioning. By using an array of chrysophyte species as food, we found multiple effects on zooplankton, which were generally negative compared to a high-quality reference food. The mechanisms include feeding inhibition, nutritional deficiency and toxicity. The results of CHRYSOWEB imply that the dominance of chrysophytes is able to significantly alter zooplankton secondary production and community composition, and therefore energy flow in aquatic food webs.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз