Oceanic fungal ecology and biogeochemistry

Microbes are the engines driving the cycling of nutrients since they have the genes encoding for the main proteins involved in the transformation of energy and matter. Thus, microbes and their activities and functions are fundamental to how the ocean operates with implications ranging from fisheries to climate change. While most of the research on microbial ecology in the oceans has been performed on bacteria and tiny marine algae, whereas fungi have been essentially neglected in open ocean studies. Most of the available studies on marine fungi are based on the isolation and identification of fungi from different surfaces (like submerged wood, sediments, large plants), mostly in coastal environments. One of the main reasons why the ecology of fungi in open ocean environments has been overlooked thus far is probably the preconception that fungi are outcompeted by bacteria when living in a resource-limited liquid environment like the ocean. However, we have recently provided evidence suggesting that fungi are present in the oceanic water column, most likely mainly associated to marine particles, with genomic potential to significantly contribute to the cycle of elements in the marine environment. Fungi are one of the main organisms responsible for the recycling of plant detritus in terrestrial and freshwater ecosystems. Thus, one might assume that the oceanic fungi also plays an important ecological and biogeochemical role in the oceans, particularly due to their high number and ubiquitous distribution of detrital particles in the sea. However, we lack even basic information on the ecology of the fungi in the open ocean (e.g. biomass distribution, growth rates, etc.) precluding us from determining the ecological role of this enigmatic kingdom in our oceans and how it might be affected by global environmental changes. We will use state-of-the-art molecular tools and adapt some techniques used in terrestrial and freshwater fungal ecology to the oceanic environment, combining lab experiments with field studies, to elucidate the ecology of the oceanic mycobiome. In this project we will quantify the numbers and biomass of oceanic fungi by using and comparing different methodological approaches, which we will fine-tune to oceanic fungal groups. We will adapt a method used in terrestrial and freshwater environments to also determine fungal growth rates in the ocean. We will apply these fine-tuned tools to oceanic samples collected in different seasons, regions and depths to uncover the main factors controlling the distribution and activity of oceanic fungi. We will also evaluate the global diversity of the oceanic fungi to reveal their contribution to the global oceanic pool and diversity of microbes. With the research proposed here, we will fill a critical gap in the understanding of the ecology and cycling of organic matter in the ocean by forging oceanic fungi as key players into the wider context of organic matter cycling.