| Corresponding to population growth and rapid development of social economy,the demand for resources is increasing.The utilization of island resources has become one of the key directions for the development of marine economy.However,the contradiction between the development of island resources and the protection of the ecological environment has been increasingly prominent due to the insular characters as separation from the mainland,small area,simple geographical structure and the vulnerable ecological system.Intertidal macrobenthos are important components in coastal and insular ecosystems,and participate in the biogeochemical cycles of carbon,nitrogen and sulfur to maintain the structure and function of the ecosystem.Because of their poor mobility and long life cycle,macrobenthic organisms are sensitive to environmental changes and are often used as indicator organisms for environmental monitoring and health assessment the intertidal zone ecosystem.Based on field investigations as well as historical data,this thesis revealed the changes and successions of macrobenthos communities comprehensively in the islands of southern Zhejiang Province over the past 30 years.The results showed that:Species number,biomass,and abundance of intertidal macrobenthos in the National Nature Reserve of Nanji islands remained stability,and significantly decreased in Dongtou islands and Beiji islands over the past 30 years.The species number,abundance,and biomass in the intertidal zone of Nanji islands,Beiji islands,and Dongtou islands were(44 species,1542.23ind/m2,2444.33g/m2),(52 species,3491.43ind/m2,2360.57g/m2)and(43 species,814.86 ind/m2,2675.32 g/m2)respectively in 1990,and changed to(42 species,1918.43 ind/nr,5295.51 g/m2),(22 species,731.56 ind/m2,1547.53g/m2),(32 species,443.11 ind/m2,1080.78 g/m2)in 2016,possible under the stress of human capture.There is an increasing but not obvious trend of subtropical species and tropical species.Shannon-Weaner diversity,evenness and richness indexes showed a decline trend.The analysis of ABC curve indicated that the community structure was disturbed with a certain degree in recent years.The stability was poor and the similarity of different communities xvas low,which was mainly affected by hu,nan disturbance and environmental changes.Totally 15 macrobenthic organisms dominated the intertidal zone in the southern Zhejiang Province in all the investigations.Except the four top dominant species such as Tetraclita japonica,Septifer virgatus,Thais clacigera and Tectarius granularis,the rest dominant species alternatively appeared corresponding to the space and time variation.Interestingly,the average body size of seven dominant species increased,e.g.the weight of individuals of Tetraclita japonica ranged from 1.32 g/ind.in 1990 to 3.22 g/ind.in 2016.The niche breadth range of each dominant species ranged from 0 to 0.97.Species with niche breadth over 0.70 showed strong environmental adaptability and appeared in most sites,such as Thais clacigera(0.97),Liolophura iaponica(0.85),Septifer virgatus(0.83),Tectarius gramlaris(0.80),C.apitolum mitella(0.80)and Tetraclita japonica(0.75).On the contrary,some dominant species only appeared in few sites with weak resource utilization capacity,such as Trichomya hirsute(0.38),Megabalanzs volcano(0.25),Mvtilus edulis(0.21),Ostrea echinata Quoy et Gaimard(0.08),Mytilus coruscus(0.08)and C.hthamalns challengeri(0).Among them,the niche overlap values among the top four dominant species were relatively larger,while the niche overlap values among the dominant species with low occurrence frequency were relatively smaller.It could be identified from the inter-species clustering and the NMS analysis that the similarities among the dominant species in the top four species,Tetraclita japonica,Septifer virgatus,Thais clacigera and Tectarius granularis,and also the species of Liolophura japonica,Tetraclita squamosal,and Capitulum mitella were higher about 70%,while the similarity between Chthamalus challengeri and other species was the lowest less than 10%.The molecular barcoding analysis of two species of Tetraclita japonica and Septifer virgatus revealed that the A+T content of the COI and 16S rRNA gene fragments was significantly greater than that of C+G,indicating that there were significant A/T bases.The low haplotype sharing rate and significant differences in Tajima's D value demonstrated that both two species had experienced significant historical expansion events.The ML tree topologies constructed from COI genes and 16s genes were consistent.Most of the individuals in the group could cluster together and also cluster with out-groups.The scattered distribution of haplotypes from different geographical groups showed no obvious geographical structure and genetic lineage structure.These might be related to the close geographical distribution.Attributing to the proliferation and enhanced protection of Thais luteostowia and Mytilus coruscus resources in the intertidal zone of Dongtou Zhuyu Island,the macrobenthic community structure in this area has undergone significant changes before and after proliferation.The species number,biomass,density and diversity have all increased considerably.The endangered Thais luteostoryia and Mytilus coruscus have become the main dominant species again in the proliferating region and the community structure has become more stable than before.According to the research,it has been found that the macrobenthic communities in the intertidal zone of the islands were degenerating and the stability and similarity of the community structure gradually deteriorated in the past 30 years.Except the dominant species with absolute advantages and low economic value,other dominant species changed significantly with time and regions,which could be attributed to human capture and large-scale climate change.The restoration of resources in the proliferating and releasing area further demonstrated that protection was extremely important to the diversity and stability of habitat community structure.Therefore,in order to protect the intertidal resources of islands,we must strengthen the habitat protection on appropriate uninhabited islands for the sustainable utilization of the intertidal biological resources. |
PDF Full Text Request