Benthic Biodiversity In The Tropical Western Pacific And The Ocean Adjacent To Antarctic Peninsula Revealed With Environmental DNA Metabarcoding

Environmental DNA metabarcoding,can be used to monitor biodiversity sensitively and efficiently,plays a more significant role in areas where traditional biological sample collection is difficult.The deep sea and polar regions are under threat from global change and human activities.It is necessary to accurately assess species diversity in these habitats and improve understanding of the biodiversity of the deep sea and polar regions.Traditional survey monitoring and morphological classification indicate that there exists rich biodiversity in deep sea and polar regions.However,it is difficult for traditional research methods to satisfy the extensive study of these extreme habitats.In this study,environmental DNA metabarcoding was used to explore the community structures and distribution patterns of benthonic fauna in the Western Pacific and the ocean adjacent to Antarctic Peninsula.V4 region of 18 S ribosomal RNA gene was selected to be amplified.Species composition,relative abundance,diversity index and community similarity were analyzed.The results of this study deepen the understanding of biodiversity of deep sea and polar regions and are of great significance for biodiversity conservation and sustainable development of marine ecosystems.The main results were as follows:(1)In the surface sediments of the tropical Western Pacific,138 genera,from113 families,59 orders,27 classes and 15 phyla were identified to be marine benthos.The dominant species were Enoplea,Chromadorea,Ophiuroidea and Copepoda,followed by Bivalves,Polychaeta,and Malacostraca.Alpha diversity index indicated that biodiversity among three regions habitats of the study area was similar.Principal component analysis and Cluster analysis based on Bray-Curtis distance matrix showed that there was no significant difference in benthos community structures among three regions,but there were significant differences among different stations.LDA Effect Size analysis showed that the significantly different species in the eastern region were Malacostraca,Bivalves,Spionida,Decapoda,Pectinoida,Cirratulidae,Pectinidae,in the middle region were Peaneidae,and in the western region were Hexanauplia,Harpacticoida,Ectinosomatidae.Canonical corresponding analysis(CCA)showed that environmental variables(water depth,latitude,silt,clay,sand,median particle size)did not have dominant factors for community structures,and water depth had the influence on community structure.(2)A total of 119 genera,from 107 families,54 orders,28 classes,and 14 phyla of marine benthos were identified from vertical distribution sediments in the tropical Western Pacific(sediment layer: 0-1 cm,1-2 cm,2-4 cm,4-6 cm).Alpha diversity index showed that the highest biodiversity was found in the 0-1 cm layer,followed by the 2-4,1-2,4-6 cm.Principal component analysis,Cluster analysis and ANOSIM test based on Bray-Curtis distance matrix showed that there was no significant difference in benthic community structures among vertical layers.The common species with high relative abundance in the four layers of sediments were Anabas,Crinoids,Sophioda,and Decapoda(Pandalidae and Penaeidae).The species with significant differences from surface to bottom of sediments were Metadesmolaimus and Bathyeurystomina,Oxystomina,Parameiropsis and Catenula,Corallimorphus and Aglaophenia.(3)In the surface sediments of the ocean adjacent to the Antarctic Peninsula,68 genera,from 80 families,47 orders,28 classes and 17 phyla were identified to be marine benthos.Phyla Annelids were dominance,followed by Nematodes,Nemertea and Arthropods.At class level,the Polychaeta is in a dominant position,followed by the Chromadorea and Enopla.Species richness and Pielou's evenness were higher in shallow sea than in deep sea,while the relative abundance of dominant species in deep sea was higher and biodiversity increased first and then decreased with the increase of water depth.Principal component analysis(PCA)and cluster analysis based on Bray-Curtis distance matrix showed that there were no significant differences in benthic communities at class and genus levels between deep sea and shallow sea adjacent to the Antarctic Peninsula.The Polychaetes have different distribution patterns in shallow sea and deep sea.The distribution former is uniform,the main dominant group is Capitellida,Maldanidae and Spionida,Apistobranchidae;while the distribution of polychaetes in the deep sea varies greatly,and the dominant groups are Terebellida,Cirratulidae and Terebellida,Ampharetidae.In this study,abundant benthonic fauna was identified in the sediments of the tropical Western Pacific and the ocean adjacent to Antarctic Peninsula with e DNA metabarcoding.It deepens the understanding of biodiversity in deep-sea and polar regions and is of great significance for biodiversity conservation and sustainable development of marine ecosystems.