The invisible fungi of the Arctic Ocean

The Arctic can feel like a place defined by what we can see: vast expanses of sea ice, towering glaciers, rugged coastlines and an ocean stretching towards the horizon. But beneath the surface, another world is constantly moving, growing and transforming matter. It is a world invisible to the naked eye, yet fundamental to how our oceans function: the world of microorganisms.

During our current research expedition between Greenland, Iceland and Svalbard, we are exploring the Arctic marine environment from different perspectives. One of the questions that particularly interests us is the role of an often-overlooked group of marine microorganisms: pelagic fungi (fungi within the water column).

When we think about fungi, we usually picture mushrooms in a forest or microscopic fungi living in soil. But fungi are also part of marine ecosystems, where they interact with phytoplankton, organic particles, bacteria and other organisms. Their role in the open ocean is still much less understood than that of many other microbial groups.

Eva Breyer and Federico Baltar on board the RV Odón de Buen.

We are interested in understanding the ecology and biogeochemistry of marine pelagic fungi: What are these organisms doing in the water column? Which environmental conditions influence their distribution and activity? And how do they contribute to the transformation and recycling of organic matter?

These questions are closely connected to the Arctic's rapidly changing environment.

The Arctic Ocean is warming rapidly, while sea-ice cover, freshwater input and seasonal patterns of primary production are changing. These changes affect not only large animals and visible ecosystems, but also the microscopic communities that drive many of the ocean's fundamental biogeochemical processes.

Microorganisms are at the interface between life and chemistry. They transform organic material, recycle nutrients and influence the fate of carbon in the ocean. Carbon produced by phytoplankton can be consumed and recycled near the surface, or become incorporated into particles that sink towards deeper waters. Fungi are part of this complex microbial network, but their contribution to marine carbon and nutrient cycling remains comparatively poorly understood.

SeaSoar: loaded and ready to be deployed to study the structure of the water column.

Of course, life on a research vessel is not only about profound scientific questions. It also involves the occasional battle against sampling equipment. Tubes mysteriously explode and turn the laboratory into a small indoor swimming pool. Sinks sometimes decide to transform themselves into miniature volcanoes. And after several weeks at sea, apparently simple things, such as remembering to bring enough toothpaste, suddenly become important logistical considerations. Meanwhile, outside the laboratory, we have a constant stream of much more impressive companions:

Northern Fulmars seem particularly convinced that a research vessel is a floating restaurant. They follow us patiently, always hoping that we might eventually drop something edible overboard. Unfortunately for them, this ship is a terrible restaurant: all waste is carefully recycled or brought back to land, and nothing is allowed to end up in the ocean. However, they wait patiently because they have time, as they can live for more than 60 years. We can only hope that, in the end, they will not turn against us and apply their common defence mechanism: they can spit oily stomach contents at their opponents, besides defecating, of course, but this is already clearly visible on the windows of our ship.

And then there are the sperm whales. Seeing these enormous animals appearing beside the ship, capable of diving to around 3,000 m and seemingly laughing at our CTD rosette as they pass it, is quite a sight. Despite being perfectly adapted to life in the deep ocean, they can also experience problems associated with decompression, similar to human divers.

These encounters constantly remind us that the Arctic ecosystem is connected on every scale, from microscopic fungi in a seawater sample to animals weighing many tons.

With every sampling station, we collect another snapshot of this changing environment. By studying the invisible communities beneath the waves, we hope to better understand not only how the Arctic Ocean functions today, but also how it may respond to a rapidly changing climate.

On the search for the "pata de jamón".

And after days of science, sampling, unexpected laboratory plumbing and wildlife watching, there is perhaps one question that sums up life on a Spanish cruise better than any scientific conclusion: "¿Dónde está la pata de jamón?"