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MARINFORSK-Marine ressurser og miljø

Bottom-sea ice Respiration and nutrient Exchanges Assessed for THE Arctic

Alternative title: Algenes respirasjon og næringsutveksling i arktisk havis

Awarded: NOK 8.0 mill.

Global warming is transforming Arctic sea ice; impacting the communities of specialised microorganisms like algae that live within it. Sea ice algae are vital members of the marine ecosystem. They supply organic carbon to grazing organisms and they influence the biogeochemical cycling of elements. Through photosynthesis, this influence includes the fixation and potential removal of the climate relevant gas CO2 from the ocean and atmosphere. Present estimates of sea ice algal production are limited by an incomplete understanding of two key processes. Firstly, how are required nutrients for growth supplied to ice algae from the ocean? Secondly, what is the energetic cost of living in the harsh conditions of sea ice? Data on nutrient supply driven by turbulent motion and algal respiratory costs (i.e. uptake of O2 and release of CO2) are needed to better this understanding. Our goal is to improve the accuracy of ice algal production estimates in a time of rapid environmental change by providing data on such knowledge gaps. Towards this goal, BREATHE combines field, laboratory and model-based investigations. To characterize algal respiration, state-of-the-art O2-based research methods are developed. They are used alongside oceanographic sensors during fieldwork across the Arctic and in the Antarctic to assess turbulent nutrient supply and algal production of contrasting sea ice habitats. The field-based work informs experiments that provide empirical descriptions of ice algal respiration under variable growth conditions. Biogeochemical modeling in the project will implement knowledge gained from laboratory and fieldwork to test parameterizations of nutrient supply and respiration. From this, modelling will be used to better predict how ice algal communities may be impacted by global warming in the future. Project outcomes will shift our understanding of ecosystem services provided by sea ice algae, like the role of microorganisms in the regulation of greenhouse gases.

Polar amplification of global warming has transformed the Arctic marine system and its sea ice cover. Reductions of ice thickness, distribution and extent have substantially impacted sea ice habitats and the microorganisms living within them. Algae are important members of sea ice microbial communities; their spring bloom kick-starts annual primary production that contributes to trophic function and carbon cycling in the marine ecosystem. However, current estimates and modeled projections of sea ice algal productivity are compromised by incomplete characterization of two key processes, i) turbulence-driven nutrient supply and, ii) algal respiratory costs of living in a harsh ice environment. Furthermore, inherent methodological constraints of studying sea ice has meant an underrepresentation of in situ measurements that are unbiased by experimental artifacts and thus invaluable for our understanding sea ice habitats. The BREATHE project will combine in situ, experimental and model-based approaches to address knowledge gaps on turbulent nutrient supply and ice algal respiration, with results that improve the accuracy of current and projected ice algal production estimates. Towards this purpose the project will develop and apply state-of-the-art O2 methods for the study of sea ice biogeochemistry. It will complete fieldwork in contrasting regions of the Arctic to characterize productivity and turbulence-driven nutrient regimes of different sea ice habitats, which will inform innovative experiments that provide the first empirical description of ice algal respiration and its variability. Integrated modeling will provide the unique opportunity to implement and directly test parameterizations of respiratory and nutrient processes, before they are applied for prediction. Project outcomes will represent a paradigm shift in our understanding of sea ice primary production, with implications for the management of ecosystem services it supports like, greenhouse gas regulation.

Funding scheme:

MARINFORSK-Marine ressurser og miljø