Mycoloop

The mycoloop is a trophic pathway in aquatic food webs where parasitic fungi, particularly chytrids, facilitate the transfer of nutrients and energy from large, inedible phytoplankton (algae) to zooplankton. This process enhances nutrient cycling and supports higher trophic levels in aquatic ecosystems.

Chytrids infect large, inedible phytoplankton, such as diatoms or cyanobacteria, and produce zoospores (free-living, motile spores, 2–5 μm in diameter). These zoospores are rich in nutrients like polyunsaturated fatty acids (PUFAs) and cholesterol, making them an excellent food source for zooplankton, such as Daphnia and rotifers. By consuming the zoospores or fragmented phytoplankton, zooplankton gain access to nutrients that would otherwise be unavailable from inedible phytoplankton, creating the trophic link called the mycoloop. In this manner, the mycoloop channels carbon, phosphorus, and other nutrients from phytoplankton to zooplankton, bypassing the limitations of inedible phytoplankton.

The mycoloop can influence phytoplankton blooms by reducing host populations (via parasitism) and supporting zooplankton growth, potentially stabilizing aquatic food webs. It can also influence the carbon cycle by altering carbon fluxes, reducing the sinking of large phytoplankton and redirecting carbon to higher trophic levels.

The concept of the mycoloop was developed by Maiko Kagami et al. in 2007. The term "mycoloop" combines myco (referring to fungi, specifically chytrids) with loop (referring to the cycle of nutrient transfer). The discovery of the mycoloop, and its potential impact on nutrient cycling indicates the importance of fungal-algal interactions in natural systems. Chytrids have also been reported to stabilize food webs, while also reducing the amount of organic material that reaches benthic environments.