Unsung ocean fungi have ‘superpower’ to aid healthy marine environments

Little-known ocean fungi are microscopic in size but make a gargantuan impact on subterranean life. Their superpower? They are the heavy lifters of carbon and nitrogen cycling, processes essential for life on earth.

Nick Peng, assistant professor in the School of the Earth, Ocean and Environment, has been studying marine fungi for seven years, five of them at the University of South Carolina. He would like unsung ocean fungi finally to get the recognition they deserve.

“Ocean fungi produce roughly three-quarters of the enzymes needed to breakdown complex biomass,” he says. Biomass refers to the total mass of living material, most of which in the ocean is produced by phytoplankton. These microscopic plants remove carbon dioxide from seawater and release oxygen through photosynthesis, supplying about half of the oxygen we breathe. Their biomass also forms the foundation of marine food webs, sustaining other marine life. When phytoplankton and other organisms die, fungi play a crucial role in recycling their biomass, making nutrients available for future production.

“Ocean fungi aren’t a big presence physically, but they have a massive impact,” Peng says.

Peng’s team collects and studies water samples from the open ocean, specifically the eastern tropical North Pacific Ocean, which is a documented oxygen minimum zone (OMZ). The prevalence of OMZs globally is escalating with climate change, as warmer water impedes the ocean’s ability to hold oxygen.

“I am excited about the interactions of fungi and bacteria,” Peng says. “They have complex relationships that can span from competition to cooperation in the microbial community.”

Much of Peng’s research is generating new evidence of ocean fungi’s substantial role in linking carbon remineralization and nitrogen cycling. Nitrogen in its raw form is not accessible to all life. Nitrogen cycling includes the process that transforms nitrogen into a chemical form that plants and other organisms can use.

While abundant in Earth’s atmosphere, nitrogen must exist in balanced quantities to be useful instead of harmful. Too much can be toxic, and too little impedes life (i.e. plant growth). “Algal blooms” are the result of too much nitrogen, which kills fish and other marine life. Those dead plants are decomposed by microbes in the water. That process depletes oxygen from the watery environment, sometimes leading to oxygen minimum zones — “dead zones” — unable to support most life forms. Fungi that live at the interface of land and ocean can filter excess nitrogen and help keep the coastal ocean balanced.

While they don’t wear capes visible to our naked eyes, ocean fungi really are superheroes of the natural world. They do so many things, from recycling dead material to producing antibiotics.

“They are one of the most important recyclers on Earth,” Peng says. “Their impact is outsized.”

Indeed. Scientists are beginning to explore applications of these tiny superheroes far beyond the Earth. It is not science fiction. The National Aeronautics and Space Administration has been planning for the likelihood of settling on the moon and even Mars.

“Fungi helped plants colonize land on Earth. Perhaps they could do it on another planet, or in space where there is no oxygen.” Peng says. In such an extreme environment, ocean fungi able to survive with low or no oxygen are excellent candidates for biomanufacturing (food/medicine/materials) and waste recycling.