Species Diversity And Distribution Of Coastal Waters Diatoms In Fildes Peninsula, Antarctica

As the base of the Antarctic food chain, Antarctic diatoms play an essential role in the Antarctic ecosystem with its species diversity and community structure characteristics affecting the stability of the Antarctic ecosystem directly or indirectly.The atmosphere, ice, oceans and creatures of the Antarctic ecosystem are closely linked with other ecosystems through biogeochemical cycles, deep ocean circulation, atmospheric circulation, and energy transport, thus affecting the Earth’s entire ecosystem.In reverse, the Antarctic region play a significant role as an “amplifier” on the global climate and environmental changes.While diatom abundance and species composition are considered to be the sensitive indicators of environmental change(e.g., climate change), the climate change of the Antarctic could also significantly affect the growth of phytoplankton species composition and succession. Although the Antarctic diatom is one of the most common algae group representatives in the Antarctic region, there are few researches about it due to the geographical particularity of the Antarctic region,hence the research about Antarctic diatoms’ diversity and distribution has universal practical significance.The diatom samples are gathered from 10 sites of Fildes Peninsula, King George Island, Antarctic. The contrastive analysis method is adopted when the diatom species composition, relative abundance of diatom cells, cell density, the dominant species, and the biodiversity index of diatom community were analyzed in this thesis. Based on domestic and overseas researches on the Antarctic diatom diversity and distribution in the recent 30 years, this thesis aims to explore the species composition, spatial distribution characteristics, and distribution rules of the diatoms community in the Fildes Peninsula. The main findings are as follows:(1)Totally, 75 diatom species(including varieties and forms, not including undetermined species),belonging to 2 classes,30 Families and species were identified. Only 10 diatom species belonging to 2 classes of Centricae,The rest diatom species belonging to Pennatae, accounted for the major part, a total of 27 classes. Thalassiosira genus is the most important species of Centricae,accounting for 63.6%. Cocconeis genus is the most important species of Centricae, accounting for 21.9%. Followed by the genus Navicula and Nitzschia genus(7 and 6 species, respectively),accounting for 10.9% and 9.4%.The entire study focuses on Nanodiatoms(2-20μm) and benthic diatoms(> 20μm).The combination of diatoms in Fildes Peninsula also exist transitional features, and its ecological features is mainly dominated by inshore cold water species and common species of Antarctic, which also gather cold water species, species at room temperature and wide temperature species. 15 species are widely distributed species, accounting for 20.27% of the number of species, including pelagic, benthic and epiphytic diatoms.(2)The number of diatom species in each site ranges from 36 to 57 species, among which the two right sites around the Great Wall and Ardley Island accounts for relatively more species, while Fuou Cove and Shengwu Cove, which spread on the north side of the peninsula, save relatively less species. There are six dominant species and eight sub-dominant species in 10 sites, most of them are endemic to the Southern Ocean or common species. Navicula glacie,Navicula perminuta have appeared in all the sites, they have an absolute advantage in microalgae, and widely distributed in the coast of the Antarctic psychrotrophic diatom typical nanodiatoms.The number of diatoms on the north side of the peninsula was less than that in the south of the peninsula, because the latter has many scientific research stations. Also, the site is located near the research station, and it probably be affected by human activities, thus the species richness and cell density of diatom in the north peninsula site is less than that in the south.The Pennatae diatoms such as Fragilariopsis sp.,and benthic diatoms Achnanthes sp.,and Cocconeis sp. are relatively common in the peninsula coast. And Centricae diatoms such as Thalassiosira sp. and Chaetoceros sp. occur frequently on the sites which is close to the seashore.(3)The cell density of diatom is relatively higher.The cell density of diatom range from 1.30 to 4.46 x 105 cells/L, the average cell density is 2.88 x 105 cells/L. The highest diatom cell density site appears in Ardley Island Bighorn, whose average density is 3.79×105cells /L. while the lowest diatom cell density site appears in Fuou Cover, whose density is 1.31×105cells /L.There exists a high biodiversity,and the diversity of the north site is higher than that in the south side, and the biological diversity expands with the increase of the number of the species of site. The Adelie Island has the highest biodiversity and species of diatom.The Fuou Cover has the lowest biodiversity and species of diatom. Changes in hydrological conditions(such as current, surface water and ice retreat time) have a greater impact on the abundance and species of diatom.The environment of each site is the main cause of its diatom evenness differences. Shengwu Cove, Ardley Island and Fengbao Cove have the highest Pielou index. With fewer species of diatom communities, Ardley Island and Fengbao Cove show a higher degree of evenness.The Ardley Island has a higher diatom species richness and high biological diversity, and the diatom community structure is relatively complex.