Arctic environments are undergoing dynamic seasonal changes affecting the spatio-temporal patterns in planktonic abundances. Studying the biogeography and biodiversity of planktonic protists and their seasonal and annual successions is necessary to better understand the structure and function of marine ecosystems. We focus on the taxonomy and ecology of arctic microorganisms larger than 20 μm, in particular diatoms, haptophytes, silicoflagellates, dinoflagellates and ciliates. These are the groups found at the base of the arctic food web that sustains the entire marine ecosystem, including higher trophic levels.
Changing sea ice conditions are expected to have a major impact on the composition and distribution of planktonic communities, which can have a cascade effect up through the food web. Many planktonic species are known as ‘bioindicators,’ as they show preferences to specific environmental conditions. Some of them live under seasonal sea ice cover, some inhabit the fresher waters influenced by the meltwater runoff from the Greenland Ice Sheet, while other species are transported by oceanic currents. This makes them very useful in evaluating changes in the marine environment over time. Furthermore, upon completion of the life cycle, planktonic remains, such as shells and cysts, sink through the water column and are buried and fossilised in the sediment, thus providing an excellent ‘bio-record’ of past environmental changes.