A main feature of cyanobacteria that makes them outcompete other phytoplankton is that they are particularly resistance to predators (i.e. zooplankton grazers). This is largely because they appear as long filaments or large colonies, which are too big be readily ingested.
From previous experiments, we already had some evidence that infection by chytrid parasites leads to the fragmentation of filamentous cyanobacteria. In our latest study, published in LImnology and Oceanography, we quantified the amount of algae that a very representative zooplankton species could ingest, both in the presence and absence of parasites. We observed in a very consistent way that zooplankton ingested about twice as much cyano biomass when chytrid fungi were infecting. As we expected, infected filaments were shorter than healthy ones, strongly indication that the fungi can break filaments, which makes them easier to be ingested by zooplankton. This phenomenon has obvious implications for the transfer of energy and matter in aquatic food webs. By making cyanobacteria more edible, chytrid parasites of cyanobacteria enhance herbivory, exemplifying how parasitism can dramatically alter the pathways by which carbon and energy flow up the food web.
Have a look at the original paper and its related press release!
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