The microbial loop plays an important role in the marine ecosystem. Studies of the microbial loop in the Arctic Ocean are limited because of sea ice coverage. Investigations have shown that the role of the microbial loop in the arctic marine ecosystem varies depending on season and region. Rapid changes in the environment, especially the decrease in sea ice coverage in summer, have been found to lead to changes in the microbial loop structure. Some studies, showing an increase of bacterial abundance and a shift in phytoplankton size structure towards small microbial eukaryotes, suggest a potential enhancement of the role of the microbial loop in the Arctic Ocean. The study of the microbial loop is an important research component, essential to the understanding of the structure and function of the Arctic Ocean ecosystem.
Results show that, for example, the structure of the arctic microbial loop is simple compared to those in low latitude areas. Bacterial production is controlled by protozoan grazing in winter, but regulated by DOM concentrations in spring and there is divergence in the ecological role of viruses in the microbial loop. However, to date most studies focus on the shelf waters of the Canadian Arctic, Chukchi Sea, Beaufort Sea and Barents Sea, few examine the central Arctic Ocean. Little research has investigated seasonal variation in the microbial loop in the basins due to logistical limitations. Apart from prochlorococcus, almost all assemblages found in the marine microbial loop occur in the Arctic Ocean. Prokaryotes are rarely reported except for bacteria.
Based on these prior studies and on the environmental changes occurring in the Arctic Ocean, the following questions should be addressed in the near future: 1) What are the consequences of the grazing of protozoa on phytoplankton and bacteria? Why does the importance of the microbial loop vary and what is the main course of these variations? Are community structure, biomass, environmental factors and / or the recent environmental changes the main factors underlying these variations; 2) What is the importance of the different assemblages in the microbial loop, such as the viruses and Achaea, which are abundant in Arctic waters but for which few data are available; 3) What are the seasonal and inter-annual variations in microbial loop processes? How do microbes of Arctic microbial loop respond and adapt to environmental change, especially to sea-ice change?