Ecology Of Macrobenthic Community In The Bridge Construction Zone At The South Bank Of Hangzhou Bay, China

Macrobenthic community is an important part of tidal flat ecosystem.Macrobentic community determines many significant ecological processes in the tidal flat wetland ecosystem. Studying on the macrobenthic community is important to improve our knowledge on the community ecology and the theory of ecology,and then it has affirmative significance to wetland resource exploitation and biodiversity conservation.The dissertation based on the research on the macrobenthic community in the middle scale at the tidal flat wetland in the bridge construction zone at the South Bank of Hangzhou Bay,China, discussed on the structure characture,spatial distribution,seasonal variation,and seasonal dynamics of macrobenthic functional groups and trophic levels of the macrobenthic community. We also study on the population and the linear regression relationships of the dominant species Helice wuana in CiXi tidal flat in summer(July,2004).Major conclusions from the research are:1.From May 2006 to February 2007,the authors studied the macrobenthic community on the tidal flat near the Hangzhou Bay Sea-Crossing Bridge at the south bank.We found a total of 32 species,belonging to 18 families,7 classes and 6 phyla,most of them were arthropods and mollusks.Species' numbers were differ significantly among seasons(F_3.6=6.58,P＜0.05),and were distinct among tidal flats was(F_2.6=75.71,P＜0.01).The density and biomass of the upper, high,middle and low tidal flat were 97.00±13.13 ind/m²,34.89±9.82 g/m²;126.00±23.08 ind/m², 33.25±9.54 g/m²;13.75±2.32 ind/m²,2.76±0.53 g/m².Densities and biomass were not significantly affected by seasons(F_3.6=0.91 and F_3.6=4.27,P＞0.05),while differences were marked among tidal flats(F_2.6=10.48,P＜0.05 and F_2.6=10.94,P＜0.01).All the zoobenthic community's diversity indices referred to in this paper were significantly different between the tidal flats,while only Margalef's species richness indices and the Shannon-Wiener diversity coefficient showed a significant difference between seasons.Margalef's species richness indices, Shannon-Wiener diversity indices and Pielou's indices were as follows:high＞middle＞low, Simpson's indexes were:low＞middle＞high.Using the Hierarchical Cluster of between groups linkage method and the Nonmatric Multi-dimentional Scaling method,the 12 macrobenthic communities of high and middle tidal flat had no distinct dividing line,the macrobenthic communities of low tidal flat had a distinct dividing line frown high and middle tidal flat.The paper indicated that habitat differences were most important reason for differences in the macrobenthic communities composion.2.A survey(May,2006 to February,2007)was carried out on the tidal flat near the Hangzhou Bay Sea-Crossing Bridge at the south bank,in order to assess the changes in habitat conditions of the tidal flat wetland resulting from differences in the zoobenthic community structure and function on different tidal flats and in different seasons.Macro-invertebrates were identified and counted.Based on the data collected from samplings near the bridge at the south bank of the Hangzhou Bay,we have categorized functional groups according to feeding types.32 species were identified,and assigned to 5 distinct functional groups(planktophagous, phytophagous,carnivorous,omnivorous and detritivorous)and 4 trophic levels.The results. showed that there was no significant difference between seasons for any of the diversity indices of functional group density,but a significant difference was found between the tidal fiats(except for the planktophagous group).The number of species in the carnivorous group showed no significant difference between tidal flats,while a significant difference was found between seasons,as opposed to the other functional groups.There was no significant difference between seasons for any of trophic levels density,but a significant difference was found between the tidal flats.The number of species placed in the carnivorous group showed a significant seasonal difference,while no significant difference between tidal flats,as opposed to the other functional groups which placed in the second and third trophic levels.This study suggests that basic zoobenthic community parameters were reflected in the composition and diversity of the functional groups.Obtaining species diversity information from the analysis of the composition and diversity of functional groups helps us to understand changes in the ecological relationships underlying complicated community changes.3.A seven-days survey(11～17,July,2004)was carried out at the CiXi tidal flat of the south bank of Hangzhou Gulf to investigate the population characters of Helice wuana,which was one of the dominant species in CiXi tidal flat.The result showed there was a highly significant difference on population density and biomass among different habitats,The density of the crabs in the reclaimed area was 23.00±5.86 individuals/m²,main road basement 10.72±2.32 individuals/ m²,tidal flat 6.36±1.43 individuals/m²,respectively,with the corresponding biomass being 172.27±43.89 g/m²(wet weight),120.28±26.03 g/m²(wet weight),61.88±13.91 g/m²(wet weight). There was a significant liner regression relationship between body length and wet weight,between body width and wet weight,especially for the goodness of fit of the latter.The author also found that there existed substantial,distinction among these samples from different habitats,as well as the discovery of the differentiation about the body length,body width,wet weigh from one Helice wuana to another,and from male to female.