Multivariate AZTI’s Marine Biotic Index(M-AMBI) was designed to indicate the ecological status of European coastal areas.Based upon samples collected from 2009 to 2012 in the Bohai Bay,we have tested the response of variations of M-AMBI,using biomass(M-BAMBI) in the calculations,with different transformations of the raw data.The results showed that the ecological quality of most areas in the study indicated by M-AMBI was from moderate to bad status with the worse status in the coastal areas,especially around the estuaries,harbors and outfalls,and better status in the offshore areas except the area close to oil platforms or disposal sites.Despite large variations in nature of the input data,all variations of M-AMBI gave similar spatial and temporal distribution patterns of the ecological status within the bay,and showed high correlation between them.The agreement of new ecological status obtained from all M-AMBI variations,which were calculated according to linear regression,was almost perfect.The benthic quality,assessed using different input data,could be related to human pressures in the bay,such as water discharges,land reclamation,dredged sediment and drilling cuts disposal sites.It seems that M-BAMBI were more effective than M-NABMI(M-AMBI calculated using abundance data) in indicating human pressures of the Bay.Finally,indices calculated with more severe transformations,such as presence/absence data,could not indicate the higher density of human pressures in the coastal areas of the north part of our study area,but those calculated using mild transformation(i.e.,square root) did. Multivariate AZTI’s Marine Biotic Index (M-AMBI) was designed to indicate the ecological status of European coastal areas. Based on samples collected from 2009 to 2012 in the Bohai Bay, we have tested the response of variations of M-AMBI, using biomass ( M-BAMBI) in the calculations, with different transformations of the raw data. The results showed that the ecological quality of most areas in the study indicated by M-AMBI was from moderate to bad status with the worse status in the coastal areas, especially around the estuaries, harbors and outfalls, and better status in the offshore areas except the area close to oil platforms or disposal sites. Despite large variations in nature of the input data, all variations of M-AMBI gave similar spatial and temporal distribution patterns of the ecological status within the bay, and showed high correlation between them. The agreement of new ecological status obtained from all M-AMBI variations, which were calculated according to linear regression, was almost perfect the benthic quality, assessed using different input data, could be related to human pressures in the bay, such as water discharges, land reclamation, dredged sediment and drilling cuts disposal sites. It seems that M-BAMBI were more effective than M- NABMI (M-AMBI calculated using abundance data) in indicating human pressures of the Bay. Finally, indices calculated with more severe transformations, such as presence / absence data, could not indicate the higher density of human pressures in the coastal areas of the north part of our study area, but those calculated using mild transformation (ie, square root) did.