Abstract
Microalgae growing on the underside of sea ice are key primary producers in polar marine environments. Their nutritional status, determined by their macromolecular composition, contributes to the region’s biochemistry and the unique temporal and spatial characteristics of their growth makes them essential for sustaining polar marine food webs. Here, we review the plasticity and taxonomic diversity of sea ice microalgae macromolecular composition, with a focus on how different environmental conditions influence macromolecular production and partitioning within cells and communities. The advantages and disadvantages of methodologies for assessing macromolecular composition are presented, including techniques that provide high throughput, whole macromolecular profile and/or species-specific resolution, which are particularly recommended for future studies. The directions of environmentally driven macromolecular changes are discussed, alongside anticipated consequences on nutrients supplied to the polar marine ecosystem. Given that polar regions are facing accelerated rates of environmental change, it is argued that a climate change signature will become evident in the biochemical composition of sea ice microalgal communities, highlighting the need for further research to understand the synergistic effects of multiple environmental stressors. The importance of sea ice microalgae as primary producers in polar marine ecosystems means that ongoing research into climate-change driven macromolecular phenotyping is critical to understanding the implications for the regions biochemical cycling and carbon transfer.
Highlights
Ice-covered seas account for approximately 10% of the global ocean surface area (34 × 106 km2) annually, with the seasonal formation and decay of sea ice playing a key role in global ocean turnover
Conducted on polar pelagic algae, this study indicates that species-specific responses likely exist within sea ice communities, which has the potential to affect food web dynamics and carbon transfer in polar regions
As light is a primary driver of sea ice microalgae primary productivity, many studies to date have focused on the effect of irradiance on biomolecular composition, with trends indicating that an increase in total irradiance dose would drive an increase in lipid and carbohydrate content but a decrease in PUFA and protein content
Summary
Ice-covered seas account for approximately 10% of the global ocean surface area (34 × 106 km2) annually, with the seasonal formation and decay of sea ice playing a key role in global ocean turnover. Whilst the contribution of sea ice microalgae to total primary productivity is generally less than that of pelagic phytoplankton, the divergence in their timing and distribution means that the sea ice microalgae subsist as an important source of nutrients and energy to the marine food web [17,20]. Their presence extends biological production in polar waters by up to three months [12], because they are the primary source of organic carbon for pelagic consumers during the ice-covered winter [15,21,22]. Accurate assessment of the direction and magnitude of these cellular changes is necessary to better understand the impact on marine biogeochemistry and carbon transfer through the polar marine food web
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