538 / 2024-09-18 11:02:35
Role of sea ice in Southern Ocean biochemical cycles between sympagic and pelagic ecosystem
Southern Ocean, sympagic ecosystem, pelagic ecosystem, nutrients, ice algae
Session 30 - Planktonic and Microbial Contributions to Marine Ecosystems and Biogeochemistry: Insights from Observations, Experiments, and Modeling
Abstract Accepted
Seasonal sea ice variation and insufficient observational techniques limit our understanding of the impact of the sympagic(ice-associated) ecosystem on pelagic(ocean-associated) ecosystem. As field observations are typically feasible only during the summer melt, nutrients and ice algae released from sea ice can't be fully evaluated, leaving the impact of sea ice biogeochemical tracers on pelagic ecosystem still unexplored. Here we utilize the Energy Exascale Earth System Mode (E3SM) by manipulating whether ocean receives nutrients or ice algae from melting sea ice to explore how those factors independently affect the Southern Ocean ecosystem. Our study findings show that sympagic ecosystem exert significant influences in the upper 20 meters of the surface ocean. When sea ice doesn't transport ice algae to the ocean, marine phytoplankton communities shift from diatoms predominantly to small phytoplankton. This shift confirms the role of ice algae as “seeds” in early spring. At the same time, surface ocean nutrients concentrations also change, with dissolved iron concentrations increasing, for example. When sea ice stops transferring nutrients to the ocean, the Southern Ocean's primary productivity decreases by about 10% and the distribution of surface nutrients becomes intricate. This complexity arises from reduced input via sea ice and the compensatory increase in nutrients due to diminished marine phytoplankton biomass. Those alterations in marine phytoplankton species and nutrients availability in the Southern Ocean also impact deep-sea carbon export and nutrients concentrations in the Antarctic Bottom Water. In summary, our research indicates that ice algae and nutrients in the sympagic ecosystem play distinct and crucial roles in marine ecosystem, thus establishing a foundation for studies on marine ecosystem related to future sea ice changes.