Study on the Changes of Macrobenthos Communities and Their Causes in Bohai Bay

Based on the analysis of macrobenthos samples collected from Bohai Bay,China in 2011 and the data obtained from the nearly the same sampling area during last six years,as well as the hydrological conditions,nutrients and dissolved oxygen,the characteristics of the changes in macrobenthos communities and their response to environmental variables were derived.Results showed that the distribution of the values of species number,abundance,biomass,richness index and diversity index reflected a gradient from the coastline to the open sea with the higher values concentrated at the open sea in the north part of Haihe estuary.The macrobenthos communities showed an obvious fluctuation over last six years,composed of three nodes.The first time node was in 2005 and 2008,the total species number,abundance and biomass maintained relatively high;the second time node was in 2009 and 2010,the values of the above three indices were the lowest in the three time nodes due to the increasing anthropogenic disturbances and natural changes;the third time node was in 2011,the values of the above three indices were the highest since many effective environmental protection measures had been carried out,indicating that the macrobenthos communities were recovered to a certain degree.The integrated impacts from the physical,chemical and biological variables induced by natural changes and anthropogenic disturbances,such as over-fishing,coastal land reclamation and sewage discharge were the triggers for the changes of macrobenthos communities.Furthermore,the variation characteristics of macrobenthic communities and environmental factors were generally in accordance with each other.