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Kostas Kiriakoulakis - Research |
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Lecturer / Senior Lecturer in Environmental Sciences |
Research interests - backgroundBiogeochemical fluxes of carbon in the ocean control its transfer from the atmosphere to the deep sea, where it may remain stored for thousands of years and form the largest carbon reservoir on Earth. Therefore oceanic controls on carbon cycling have serious repercussions for climate. Furthermore, carbon fluxes into the ocean interior provide the main energy source for many benthic and pelagic ecosystems. The vast majority of marine organic matter is produced in the surface of the ocean (ca. first 100 m) by phytoplankton through photosynthesis. Phytoplankton is then grazed mainly by zooplankton or dies and sinks. Over time the "rain" of sinking particles rich in carbon remove large amounts of CO2 from the atmosphere (a process known as the biological pump), thus playing a important role in regulating of Earth's climate. Many questions however remain. For example how much organic carbon escapes the first 100 metres into the ocean interior? Does the ratio of produced carbon vs. escaped (or exported) carbon change spatially and temporally (with season or from year to year)? Does phytoplankton composition affects the sinking process? How do different zooplankton communities respond? Do ocean currents, tides and ocean topography affect the sinking processes? What is the impact of the changing climate to primary production and the biological pump? Furthermore the organic detritus that falls into the oceanic interior is the major energy source of most deep sea (benthic) ecosystems which occupy 50% of the planet. However we know surprisingly little about the fate of organic matter as soon as it escapes the first 100 m and how it affects deep sea ecosystems (e.g. their distribution, biomass, diversity). For example the origin and transformations of organic matter often determine its bioavailability (e.g. terrestrial organic matter is more recalcitrant than marine organic matter); this is important in understanding the functioning of marine ecosystems and the ultimate fate of carbon in the ocean. My approach: biomarkers and isotopesThe chemical composition of water particles and sediments holds invaluable information about the recent and past carbon and nitrogen cycles. For example certain chemical compounds such as lipids (e.g. fatty acids and sterols), pigments (e.g. chlorophyll products and carotenoids) or some amino acids can retain information on their biological origin. These compounds are thus labelled biomarkers and their distributions used together with their carbon and nitrogen stable isotopic composition (also diagnostic for origin, burial or trophic modification) can shed light to the transformation pathways of marine organic matter and thus the cycling of carbon in the ocean. Research projectsCurrent projects:
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