Characterizing mycoplankton and the mycobenthos in the Benguela upwelling system

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The "biological pump" exports biologically produced organic matter in the surface ocean to the deep sea and seafloor. The efficiency of the biological pump exerts a strong influence on Earth’s climate by controlling how much carbon is exported to the deep sea and biodegradation of the organic matter deposited in sediments controls massive (teragrams) sinks of organic carbon that are ultimately sequestered in the subsurface. The mycoplankton and mycobenthos are two groups of heterotrophic eukaryotic microbes that are hypothesized to help control the flux of carbon in seawater and sediments, but the abundance, diversity, and activity of these groups are poorly understood.Mycoplankton and the mycobenthos are Fungi and fungal-analogs that live in seawater (mycoplankton) and sediments (mycobenthos), respectively. They have been detected in several locations of the world’s oceans. Thus, through their metabolism they are hypothesized to help control how much organic matter is ultimately buried and sequestered in the seafloor on a global scale. However, mycoplankton and the mycobenthos have not yet been characterized in the Benguela upwelling system. Because this is one of the most productive upwelling regions of the ocean, the overarching research aim of the proposed work is to quantify mycoplankton and mycobenthos diversity and metabolic activity, in order to better define their ecological role in this important oceanographic location. To this end, I participated in the Meteor Reise M148-2 to the Benguela upwelling system ('EreBUS': Processes controlling the Emissions of greenhouse gases from the Benguela Upwelling System) from July 2nd – July 20th, 2018. Waters were sampled from six sites exhibiting vertical oxygen gradients that were observed in the water column on the Namibian shelf. In addition, two 26 cm deep sediment cores were obtained from one site below the oxygen minimum zone on the shelf. Water samples up to a depth of 1,000 m were also collected at eight offshore sites in the Angola Gyre, as the Meteor transited from Namibia to the Canary Islands. In total there are 90 samples that now await processing, and I propose to use state-of-the-art quantitative DNA and RNA sequencing techniques to determine the abundance, activity, and diversity of the mycoplankton and mycobenthos.The proposed project will address the questions: What are the dominant groups of metabolically active mycoplankton and mycobenthos in the Benguela upwelling system? What are the biogeochemically relevant metabolic features of mycoplankton and mycobenthos in the Benguela upwelling system? Addressing these questions is important because it will improve our understanding of a new biological mechanism (mycoplankton and mycobenthos) within the biological pump, a global process that helps control Earth’s climate over geological timescales.