Study On Annual Variations In Community Structures Of Periphytic Diatoms And Relationships To Environmental Conditions In Coastal Waters Of The Yellow Sea, Qingdao

Community parameters of diatoms have been used as useful bioindicators for bioassessment of both lentic and lotic systems. Sampling strategies and colonization dynamics of periphytic diatoms were studied in coastal waters of the Yellow Sea, near Qingdao, using glass slides as an artificial substratum. And the temporal variations in community structures of periphytic diatoms and relationships to environmental conditions were also investigated in coastal waters of the Yellow Sea from January to December in 2013.As a result of the survey, the analysis of the sampling strategies and colonization dynamics of periphytic diatoms reveals that (?) Enumeration time periods (within 24 h and 24-48 h) represented a significant influence on detecting the community features of periphytic diatoms. The delayed enumeration (within 24-48 h) may result in the similarity of the communities being reduced 10%-29%, and in diversity (richness, evenness, and diversity of species) indices decreasing and in species numbers decreasing and in abundance increasing with exposure duration, respectively. These results suggest that the enumeration scheme (within 24 h) was more effective to detect the ecological features for assessing water quality in marine ecosystems. (?) The colonization process of periphytic diatom communities in coastal waters might be assigned into three stages:the initial (1-3 days), transitional (7 days or more) and the equilibrium (10-28 days) stages. During the equilibrium stages, the diversity indices of periphytic diatom communities showed significantly high similarities, but represented a significant difference compared to those during the initial and transitional stages. Thus, it is suggested that the colonization ages of 10 days or more might be considered sufficiently mature communities of periphytic diatoms in coastal waters of the Yellow Sea. (?) The dynamics of diatom colonization process had a similar pattern in community structure and were fitted the logistic model in growth curve at both depths. The maximum abundance (Aman) and the time for reaching 50% Amax (?10 days) showed no significant differences between two depths 1 m and 3 m at both depths (P> 0.05). The diatom communities differed in temporal pattern of structural parameters and in succession dynamics of dominant species between the two layers. And that the sampling strategy at 1 m was more effective to detect the ecological features for bioassessment in marine ecosystems.The anlysis of temporal variations in community structures of periphytic diatoms and relationships to environmental conditions reveals that(?) the results of ANOSIM analyzing and PERMANOVA+analyzing showed that the environmental factors at different seasons were significantly different in costal waters of Qingdao. (?) A total of 33 periphytic diatom species were identified and the abundance values of Nitzschia closterium ? Bacillaria paxillifera? Navicula directa? Diadesmis contenta and Nixtzschia longissima were high during the period of study. (?) The main dominant species in different seasons were varied, the dominant species in spring included Nitzschia closterium and Navicula directa, in summer included Nitzschia closterium and Bacillaria paxillifera, in autumn included Nitzschia closterium? Bacillaria paxillifera? Surirella fastuosa and Navicula ramosissima, in winter included Navicula directa. (?) The abundance of periphytic diatoms had a bimodal pattern in July (6850 cell/cm2) and November(32411 cell/cm2), a sudden increase in Nitzschia closterium and Navicula ramosissima resulted in the highest values of abundance in November. (?) The results are provided to show that different seasons can be separated through CLUSTER analysis, MDS ordination and CAP analysis. The result of ANOSIM analysis was shown that there were significant differences among different seasons. (vi) Diatomes exhibited a classic bimodal pattern of richness? eveness and diversity in May and November, the value of diversity index was highest in autumn, the diversities of periphytic diatoms were the highest in autumn and lowest in winter. (?) RELATE/BIOENV analysis revealed that there was a significant correlation between temporal variations in periphytic abundances and changes of environmental variables, especially temperature, salinity, pH, transparency, COD and nutrients in combination (P<0.05). (?) Transparency and salinity were significantly positively correlated with the abundance of diatoms, salinity was significantly positively correlated with richness and the species numbers,but temperature was significantly negatively correlated with richness. Navicula directa was generally significantly positively correlated with transparency, and significantly negatively correlated with SRP, NO2-N and SiO3-Si; Nitzschia closterium was generally significantly positively correlated with transparency; Bacillaria paxillifera was generally significantly negatively correlated with pH; Surirella fastuosa was generally significantly positively correlated with SRP.This survey further explored an effective sampling and enumeration strategy to collect the diatom communities for monitoring water quality in marine ecosystems. And trace the temporal variations in community structrues of the diatom and relationships to environmental conditions.