Polar microalgae as indicators of environmental change

Abstract

Polar ocean plays an important role in the carbon cycle. The carbon cycle could change in the near future in response to rising CO2, surface temperature and stratification, which may reduce capacity of take up CO2 of human origin. There is increasing interest to better understand the ecology of the polar ocean. Models predict that global warming will have a major impact on the biogeochemisty of the polar ocean via changes in upper ocean stratification and microalgal community composition. Understanding the factors controlling species composition of microalgal blooms is important because microalgal taxa can vary considerably in terms of their biogeochemistry and their functional role within their respective ecosystems. Taxonomic differences in photophysiology may strongly influence microalgal community composition. Polar marine microalgae can be used as tracers of various environmental parameters. Microalgal assemblages known to be closely associated with sea-ice can be used as tracers of sea-ice cover. The close relationship between sea ice affected areas and sea ice-related microalgae in water samples, the sediment trap, and the surface sediment record by their distribution pattern makes their distribution pattern a proxy of sea-ice reconstruction in the past. If near-shore and shelf assemblages are found in deep waters, these forms are indicators of lateral transport. Freshwater assemblages found in marine sediment provide evidence of either fluvial or eolian transport. High abundance of bloom-forming taxa reflects condition of rapid nutrient uptake and growth rates, while aggregates of large mat-forming taxa may indicate conditions of prolonged water column stability.Past field and laboratory studies have not provided definitive measurements of the taxon-specific ecological and physiological characteristics that may explain patterns of horizontal distribution or that can be used for the parameterization of biogeochemical models. Even many biological markers (