Tag Archives: phytoplankton

Parasites: Maybe They’re Good?

Infection of filamentous phytoplankton by fungal parasites enhances herbivory in pelagic food webs (2020) Frenken et al., Limnology and Oceanography. https://doi.org/10.1002/lno.11474

Image Credit: MarekMiś, CC BY 4.0, Image Cropped

The Crux

Pelagic ecosystems (see Did You Know) make up more than 70% of the Earth’s surface, and the base of the food web is composed of primary producers like phytoplankton. Primary producers produce their own energy and provide an important service to the rest of the food web (and planet!). Not only do they provide a resource for the upper levels of the food web, but they also contribute to the global climate by making carbon available to other organisms. Because of these large-scale ramifications for any changes in phytoplankton primary production, many studies have investigated how things like nutrients, light, and temperature are able to affect phytoplankton.

A key aspect of certain phytoplankton is that they have morphological characteristics that make them more resistant to consumption by grazers further up the food web, like zooplankton. However, chytrid parasites (the same fungus that is ravaging amphibian populations the world over) are able to get around these defenses and reconnect phytoplankton to their zooplankton consumers. Chytrid infects phytoplankton, it then releases a free-living infectious stage, the zoospore, which is eaten by zooplankton. This indirect connection between inedible phytoplankton (like cyanobacteria) and zooplankton is called the mycoloop, and it can provide zooplankton with up to 40% of their food. Interestingly, studies have shown that zooplankton populations do better when their food, the inedible cyanobacteria, is infected by chytrid. Today’s study investigated how exactly chytrid is able to reduce the cyanobacteria defenses and provide zooplankton with more food.

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