Focus 3 will target how the combination of loss of land ice and sea ice affect community composition and food web structure in Arctic coastal areas.
Theme 3.1 – Elucidate the effect of ice loss on primary producers.
Primary production, the basis of the marine food web, is mainly controlled by light and nutrient availability. In the current Arctic, spring primary production starts with shade-adapted algae on the underside of the ice. Ice thaw creates a shallow nutrient-poor surface layer, below which there is enough light and nutrients for high phytoplankton production. In summer, thawing of land ice and increased freshwater run-off enhance this stratification, reducing nutrient availability and pushing production down into light-limited depths. Still, some production continues until light finally disappears with the onset of winter. During winter, convective mixing and brine release ensure plentiful nutrient supplies when the light returns. In the ice-free Arctic, the intricate seasonal balance of all these processes will change, disrupting primary productivity. Ice forming and thawing intermittently may disrupt the balance of production between ice algae and phytoplankton, and increased freshwater runoff could enhance stratification, with more nutrient limitation much earlier in the season. These changes may allow an entirely new ecosystem structure and function to develop.
Theme 3.2 Understanding the net effect of ice loss on community structure and food webs.
Freshwater input and the transition from ice-covered to open water conditions may significantly influence the diversity and composition of pelagic marine communities, impacting ecosystem structure and productivity. Environmental DNA (eDNA) analysis provides a powerful method to study these communities. Aquatic ectotherms' geographic ranges are shaped by physiological performance, which may be affected by changes in water temperature, salinity, and prey intake due to ice loss. To assess the impact of an ice-free Arctic on marine fishes, we will estimate the field metabolic rate (FMR) of Atlantic cod, sculpin, and charr. By subtracting standard metabolic rates from FMR, we will evaluate energy expenditure beyond maintenance as an index of physiological performance along environmental gradients. Integrating hydrographical, biogeochemical, and eDNA data, we aim to uncover drivers of community composition along high-latitude climate gradients. Changes in community composition are expected to alter trophic structures, leading to novel food web configurations and shifts in productivity.
