Study On Community Ecology Of Macrobenthos In The Tidal Flat Wetland Of Jiaozhou Bay

Benthic fauna is an important group in the marine ecosystem, which belongs to theconsumer components and plays a vital part in the material circulation and energy flow inthe ecosystem. It is of great significance to study the species composition, distribution andcommunity structure of macrobenthos, considering the aims of conservation of our marineenvironment and the sustainable exploitation of biological resources. In this thesis, the tidalflat wetland in the northwest of Jiaozhou Bay was investigated, and the macrobenthos weresampled for12months from February2009to January2010. Based on the survey data ofabundance and biomass of macrobenthos, several studies were conducted, includingresearches on species composition, the dominance, spatial and temporal variation of theabundance and biomass, the secondary productivity, assemblage structure and diversity ofmacrobenthos. Furthermore, environmental disturbances to the community were assessedand the relationship between the main environmental factors and macrobenthos wasdiscussed. Differences of the tolerance to various environmental factors betweenpolychaetes were analyzed, and the main influential factors were discussed.The results showed that totally97species of macrobenthos were identified in thesurvey around the year, including polychaetes of26species, crustaceans of24and molluscsof35. Others species involve fishes, echiura and echinodermata et al., amounting to12species. The main dominant species are Ruditapes philippinarum, Potamocorbula laevisand Sinonovacula constricta.The distributions of macrobenthos in the tidal flat of Jiaozhou Bay concentrate on theupper part of the middle tidal zone and the low tidal zone, considering the spatialdistribution. Polychaetes have a concentrated distribution in the mid-low zone; Crustaceansconcentrate in high tidal zone and molluscs concentrate in middle and low tidal zone. Heterogeneities in hydrology and sediment in a small scale and the disturbance fromaquaculture may be the main reason for the uneven distribution of macrobenthos in the tidalflat of Jiaozhou Bay.The mean abundance of the macrobenthos in the studied tidal flat is289.6ind/㎡，andthe mean biomass is169.7g/㎡. The abundance increased from Feb.2009and reached themaximum in August, then decreased sharply. The trend of biomass was generally the same.Considering the main taxa, the abundance of Polychaetes has similar annual variation to theladder-shape; the quantity of crustacean has little fluctions among months; molluscs show asignificantly single peak. The aquaculture of bivalve has decisive influence on the temporalvariation of macrobenthos.The secondary productivity of macrobenthos in the studied area varies between5.33to29.90g AFDW· m^-2· y^-1, depending on the three models used in the estimation, Brey90,T&D and Brey01. The difference between the results from the three models are significant（p<0.05）. Considering the temporal variation, the secondary productivity is highest insummer, followed by spring and autumn, lowest in winter. The productivity is highest inlow tidal zone, followed by middle and lowest in the high zone considering spatialdistribution. The aquaculture activities may be the main reason for the spatial-temporalvariation in the secondary productivity of macrobenthos.The tendencies of biodiversity reflected by the four diversity indices were similar,which showed the minimum in July and achieved high value in February, March, Novemberand December. There is a significant correlation between Shannon-Wiener, Pielou andSimpson index. Most of the researching months show mild or moderately pollution and onlyJuly show heavy pollution, regarding the Shannon-Wiener index. The abundance/biomasscomparison curve illustrated a similar trend, indicating heavy disturbance in July,September and January. Hierarchical clustering analysis showed that3groups could bedivided from the12sampling months, corresponding to3kinds of environment qualityrespectively. Ruditapes philippinarum, Potamocorbula laevis and Musculus senhouseicontribute mostly to the differences between the divided groups. There was no significantcorrelation between the main environment factors and biodiversity indices or communitystructure. Totally24taxa of polychaetes occurred during the survey period with the dominantspecies of Amphictene japonica and Heteromastus filiforms. The mean abundance ofpolychaetes is13.7±10.3ind m^-2, and the variation was not significant between samplingstations or months. The assemblage structure differed significantly between samplingperiods according to MDS, which was discriminated mostly by the abundance of A.japonica and H. filiforms. The study reveals significant relationships between thepolychaete assemblage and the environment factors, including natural environmentfluctuation and anthropogenic activities. The abundance of Potamocorbula laevis, contentof arsenic, temperature and dissolved oxygen may be the mainly influential factors to thepolychaete assemblage. The susceptibility of polychaete to these environmentaldisturbances differed significantly and H. filiforms, Marphysa sanguinea, Glycera rouxi andLumbrineris heteropoda turned out to be the potential indicators to the correspondingpollution substance.