Community Structure Characteristics And Environmental Implications Of Heterotrophic Flagellates In Polar Area

Under the influence of global warming,the ecosystems of the global seas are changing.Due to its geographical location and climatic conditions in polar regions,climate change has a more obvious impact on microbial ecology and food webs in polar land-sea ecosystems.The melting of sea ice and the increase of open seas directly affect the marine environment and ecosystems.The relationship between the trophic levels of the marine food loop in the North and South Poles is relatively simple,and there are few nutrients.The microbial food loop in the polar seas has a much greater effect than in other seas.It is the main channel for energy flow.Heterotrophic flagellates play a central role in marine food loop.Existing studies have shown that heterotrophic flagellates have different taxonomic components in different geographical regions.Heterotrophic flagellates are a potential indicator species for environmental changes.Different ocean water masses have different heterotrophic flagella communities.There are few studies on the spatial distribution and diversity of heterotrophic flagellates.Therefore,based on the research needs on the impact of sea ice ablation on the structure of the ocean system under the background of global climate change,the Powell Basin of the Antarctic Peninsula in the southern hemisphere summer of 2011-2012,the Pacific Sector of the Arctic Central Ice Zone in the northern hemisphere summer of 2016,and the Astronaut Sea summer of 2019-2020 were studied.This paper demonstrated on the spatial distribution characteristics of heterotrophic flagellates in the three target regions of the Antarctic Ocean and the Arctic Ocean.Using high-throughput sequencing,this study screened out a variety of heterotrophic flagellates.The major effect of this study was toanalyze the species and its comparison in the of the Antarctic Peninsula surrounding areas.The community structure and dominant species of heterotrophic flagellates in different habitats include sea water,Astronaut Sea,sea ice,subglacial sea water,and surface snow in the Pacific sector of the Arctic Ocean,and explore their differences in different regions and habitats sex and similarity.By analyzing the correlation of environmental factors and indicator species,we can understand the differences in the response of different populations of heterotrophic flagellates to environmental factors in the polar seas.Moreover,it was possible to explore the factors that affect the differences in community structure and dominant populations,and the possible environmental indicator capabilities of indicator species.The potential changing trend of heterotrophic flagellates population structure in the Arctic and Antarctic was exhibbited global climate change.Except for the surface snow,Cryomonadida appears as an indicator species in different environmental media in the central Arctic ice area.Cryomonadida and Dinophyceae all dominated the ice core,0m subglacial seawater,melt pool and surface snow samples,and in 2m,5m and 8m subglacial seawater samples,Dinophyceae,MASTs and Picozoa started at most stations gradually occupy the abundance advantage.Most environmental parameters(temperature,salinity,phosphate,nitrate,silicate)had moderately significant correlation effects on various species.The melting of sea ice in the central Arctic ice region,the Beaufort Circulation and the Circumpolar Current also affect the diversity of heterotrophic flagellates communities.In the Powell Basin,north of the Antarctic Peninsula,both micro-and picoheterotrophic flagellates have the same dominant population(MASTs and Telonemia),and the indicator species are Cryomonadida and MASTs.Heterotrophic flagellates with different particle sizes showed different degrees of abundance and diversity.The correlation of nano-heterotrophic flagellates with environmental factors was stronger than that of pico-heterotrophic flagellates.The main variables affecting heterotrophic flagellates diversity and community structure are salinity,bacterial biomass,and biological interactions among various groups.Various parameters such as temperature,salinity,chlorophyll a concentration and nutrients may affect the diversity and abundance of heterotrophic flagellates.In the Antarctic Astronaut Sea,the main indicator species in the middle and upper waters of the western sea area is Cryomonadida,and the main indicator species in the eastern sea area including the deep water in this area are MASTs.At the same time,the abundance of heterotrophic flagellates showed a trend of increasing and then decreasing from the sea surface with the increase of water depth.The correlation between most populations and environmental factors is weak,but the correlation between species is more significant.The differences in the community structure of heterotrophic flagellates may be more related to the interaction of ocean currents and water masses.The differences in the distribution of dominant populations ligned with the distribution of various ocean currents in this region.The distribution of heterotrophic flagellates in the deep water layer was affected by the Antarctic bottom water mass and overturned circulation effects.Under the background of global climate change,the future Arctic ice area will continue to have a large amount of freshwater input.The salinity of seawater will decrease,and the heterotrophic flagellate populations will change to high temperature and low salinity habitat population.At the same time,the populations of Dinophyceae,MASTs,Telonemia,Picozoa and Choanoflagellates will decrease relatively.Some populations with branches of freshwater species,such as Telonemia,may occupy more ecological niche.In the Antarctic waters,compared with other environmental factors,ocean currents and sea ice flow have a greater impact on heterotrophic flagellates community structure and differences in dominance.Due to the complexity of the food web in the middle and upper layers of the Southern Ocean and the differences in topography,hydrology and glaciation,the response speed of the ecosystems in the Southern Ocean to global warming is slower than that of the Arctic.Heterotrophic flagellates communities also responded when there was a significant impact on sea ice boundaries.