Distinctions in quantitative distribution, structure and rates of development of phyto- and zooplankton are connected with the temperature influence, related to ocean currents and the distribution of the ice and the ice edge. Many species of phytoplankton have a rather wide tolerance range for parameters such as temperature and salinity, and also adapt to different levels of light down to its very minimum. However, some of the species in the Barents Sea are connected to colder water or ice edges, with more specific demand in these parameters. For species with a more narrow tolerance in these parameters changes will have a strong effect on their distribution and abundance.
Large changes in these parameters could result in changes in the overall phytoplankton community composition, changes that could be critical for some species and their predators. However, in most cases such changes might only have a negative effect on the specific species, whereas the overall structure of the phytoplankton could be unaltered since “new” species could take up there ecological role in the food web.
Variation in the climate, explicit as ice cover, could affect the annual primary production. Models of primary production indicate that years with higher temperature and higher inflow of warmer Atlantic water result in a higher annual primary production (new production) in the Barents Sea (Figure 2.6.1). The observed annual changes in the model primary production are explained by the percentage of ice free water masses. The annual average production becomes lower in those year when the ice is widespread and if the melting of the ice occur later in the season. Even thought production in the ice edge and polar front could by high (measured as chlorophyll a) it only covers a narrow area along the edge and occurs in a short time period, and the portion to the total production is therefore low, except for years when the ice is widespread.
For zooplankton, variation in temperature, currents and ice distribution can have strong effect on individual species. The strongest effect of this is seen in the Arctic species Calanus glacialis, which is usually connected with cold Arctic water, unlike C. finmarchicus which is more related to the inflow of the Atlantic waters. Cold water also slows down the growth and maturation of copepods. Potential changes in the microzooplankton community are hard to evaluate as the knowledge of these groups and species from the region is very limited.
