| The zoobenthos and some environmental factors in coastal waters and intertidal zone of Bohai Bay were investigated and tested on July, 2003, November, 2003, February, 2004 and May, 2004 respectively. The ecology of macrofauna and meiofauna was studied and quality of some economic organisms and environmental factors was tested. In addition, the indices of macrofauna and meiofauna were used to evaluate the health conditions of marine ecological system of Bohai Bay at first time and the diagnosis system of deterioration of coastal habitat and monitoring technology of habitat deterioration with biological indicator or population was established preliminarily. The detailed results are as follows.1.Study on Marine Environmental FactorsIn the bottom water, three main nutritive salts ( Nitrate, Phosphate and Silicate) exceeded the standard of seawater quality of Level I in a majority of sampling stations in Bohai Bay. Moreover, the concentration of them in nearshore waters was higher than that in offshore waters, that is to say, the higher values appeared in estuary and auqcultural areas and the lower values was found in offshore areas. Besides, the heaviest pollution occurred in spring, the second heaviest pollution in autumn and the slightest in summer. The detectable rate of oil was 100% in 22 sampling stations during three cruises and nearly 60% ofsamplings exceeded the standard. Moreover, the concentrations of oil in estuary and nearshore areas were higher than that in offshore waters and the highest density of oil appeared in autumn and lowest in summer. Among six heavy metals, the pollution of Zn, Pb and Hg was seriously.In the sediment of the studied areas, chlorophyll a (Chla) and pheophorbide a (Pha) showed a similar trend that the contents in surface layer (0~2cm) were higher than in the bottom layer (2~ 5cm) . Moreover, the density of them in nearshore stations was lower than that in offshore stations and the value appeared highest in summer, higher in autumn, lower in winter and lowest in spring. The content of organic matter in nearshore stations was higher than that in offshore stations and the higher value appeared in summer and lower value in spring. In addition, the variation of water content in the sediment was very little. The concentration of Zn, Cr and Hg exceeded the standard in all studied stations , so did Pb in station A9, A10 and A15 and Cd in station A5.2.Study on Macrofauna Ecology149 kinds of macrofauna were obtained from this investigation. The average richness, biomass and production of four cruises were 618 inds./m2, 27.62 gw.w./m2 and 1.33 gAFDW/m2a respectively. The average richness, biomass and production in summer were respectively 375 inds./m2, 56.18 gw.w./m2 and 2.54gAFDW/m2a; 483 inds./m2, 36.02 gw.w./m2 and 1.77 gAFDW/m2a in autumn; 719 inds./m2, 10.93 gw.w./m2 and 0.58 gAFDW/m2a in winter; 894 inds./m2, 7.34 gw.w./m2 and 0.41 gAFDW/m2a in spring. Seasonal variation of richness is spring> winter > autumn > summer. However seasonal variation of biomass is summer>autumn>winter>spring. Furthermore, the total secondary production of macrobenthos is approximately 20,000 tAFDW/ a If we take 15,000 km2 as the total area of Bohai Bay.The results of analysis on the diversity of macrofauna showed that population number and dominant species varied and alternated in seasons. Base on the CLUSTER analyses of all cruises and sampling stations, the studied stations could be divided into three groups, the nearshore stations, the offshore stations and middle groups according to the similarity between the community structure,. The average values of Shannon-Weiner diversity index (H') of four cruises were 2.64 in spring, 2.51 in summer, 2.70 in autumn and 2.52 in winter respectively. One-Way ANOVA analysis indicated that all the difference was not significant(p>0.05) , that is to say, the variation of H' in different seasons was not obvious.Macrobenthos were closely correlated with bottom water and sediment environment. The richness, biomass and production Macrobenthos was significantly positively correlated with Chla, Pha in sediment, water depth, as well as Chla and oxygen content in water body. In addition, they had negative or significantly negative correlation with the concentration of oil and heavy metal and they were positively or negatively correlated with other factors, but the correlation was not significant. The diversity of macrofauna had significantly positive correlation with Chla, Pha in sediment, depth, as well as Chla and diaphaneity in water body. Moreover, the diversity was always significantly negative correlated oil,heavy metal, carbon, total nitrogen, total as well as phosphate content. Besides, they were positively or negatively correlated with other factors, but the correlation is not significant.The community structure of macrobenthos has changed in the last 20 years in a certain degree. The change was probably due to the variation of marine ecological environment, disturbance of sediment, high-speed eutrophication process, fishery activity and the change of benthos predator.3.Study on Meiofauna Ecology11 species of meiofauna were obtained and identified from this investigation. In terms of the richness, diversity and biomass, free-living marine nematode and benthic copepods were two main species, whose richness could be more than 96%. The average richness, production and biomass of meiobenthos in four cruises were 570.4±143.5 ind.10cm~2, 313.5±121.5 ug dty w. 10cm"2 and 2821.8±1097.7 ug dty w.10cm"2a"1 in summer respectively; 489.4±125.3 ind.10cm"2 , 280.2±107.6 ug dty w.10cm"2 and 2521.8±968.7 ug dty w. 10cm~2a*1 in autumn respectively ; 653.8±146.2 ind.iOcm"2 , 369.0±117.2 ug dty w.10cm"2 and 3321.1±1054.8 ug dty w.10cm"2a"1 in winter respectively ; 762.5±187.7 ind.10cm"2 , 488.2±204.1 ug dty w.10cm"2 and 4394.1±1836.5 ug dty w.10cm"2a"1 in spring respectively. In addition, the dynamic change of the richness, biomass and production showed a similar regularity.The richness, biomass and production of meiobenthos in all cruises and sampling stations had significantly positive correlation with water depth and Chla in waterbody (p<0.05) and Chla, Phain sediment ( p < 0.01 ) . Furthermore, they have negative correlation with the density of oil, Pb, Cu, T-Cr, As, Hg, Zn, suspened solid, diaphaneity and grain diameter of sediment. The variation of the density, biomass and production of the meiobenthos may be caused by environment pollution in Bohai Bay and some regulation macrofauna preying on meinfauna.4.Study on Entironment Monitoring and Assessment of Bohai BayThere was of advantage to monitor and evaluate marine environment by using index of benthos. Different methods could indicate the basic conditions of the marine quality of Bohai Bay in different aspects though each method had its limitations. The analysis of organism quality of the investigated area showed that in this area, the content of Cu exceeded the standard seriously and was the main pollutant. Besides, the PAHs in organism were also above the threshold. The levels of pollution assessment could be preliminary determined by the percentage of major components of macrobenthos, the ebb and flow of tolerance species and sensitive species an the results indicated that the heavier pollution occurred in spring and winter and the pollution was heavier in nearshore stations than in offshore stations. Echinoderms often appeared in clean areas. The richness/biomass curve (ABC curve), Shannon-Weiner diversity index (H1) and N/C index could all reflect the healthy status of biocenosis in Bohai Bay. In addition, the comprehensive analysis suggested that the degree of pollution or disturbance declined obviously from nearshore stations to the offshore stations. The station A11 is the cleanest one, while station A5, A9 and A20 are seriously polluted or disturbed and otherstations were moderately polluted or disturbed.In conclusion, as one of the four largest sea areas in China, Bohai Bay is also one of the first typical bays, where the ecosystem has been investigated initially and the research achievements is fundanmental for the studies of marine ecosystem research in China. The studies of zoobenthos ecology in Bohai Bay is not only to provide theoretical basis for health status assessment of ecosystem in Bohai Bay, but also is greatly meaningful to scientifically manage and utilize macrobenthos resources, to realize dynamic changes of benthos biocenosis, to monitor environment variation in Bohai Bay and to explore the sustainable utilization of resources in Bohai Bay. Meanwhile, this research will be combined with the Activity Plan for Cleanning in Bohai properly and the results will provide beneficial technological support to the improvement of the quality of ecosystem in Bohai bay and the diagnosing and monitoring technology can directly serve the protection of coastal environment and management decision of government.This study was supported by High-Tech projects (863) and was the sub-program of "Restoration Technology of typical habitat in Bohai" (Number: 2002AA648010).
|
PDF Full Text Request