Spatiotemporal variation of benthic biodiversity under persistent and extreme human disturbances in the Xiamen sea area, China

Abstract This study uses benthic macroinvertebrates as indicators to analyze the variational characteristics of benthic biodiversity under persistent environmental pressures, such as rapid economic and population growth, large-scale urbanization, rapid tourism development, intensified port activities, and extreme human disturbances such as reclamation and dredging, in the Xiamen sea area during 1980–2016. From 1980 to 1990, benthic biodiversity in the area generally remained high, with a species richness of 13, individual abundance of 584 ind/m2, biomass of 79.58 g/m2, and a Shannon diversity index (H′) of 3.26. Under persistent environmental pressure, this biodiversity significantly declined from 2005 to 2007, but improved during 2013–2016 as a result of measures such as establishing reserves, prohibiting aquaculture, and controlling the inflow of pollutants. Under the extreme disturbance caused by reclamation, the average species richness, individual abundance, and H′ of the Tong'an Bay (TB) and the Dadeng sea area (DS) declined considerably. The DS closer to the open sea experienced a benthic biodiversity decrease (25.2% on average) that was significantly less than the decrease in the semi-enclosed TB with a smaller area (55.8% on average), which stopped declining after the sharp drop in the first year after reclamation. This contrasts with TB, where benthic biodiversity six years after reclamation remained considerably lower than before reclamation. However, the decrease in the local total species richness caused by reclamation can be recovered, regardless of whether it is in the open DS or the semi-enclosed TB. Under the extreme disturbance of dredging, individual abundance and biomass in the dredging areas were significantly lower than the average for the study area in 2005–2012. However, following the completion of dredging in 2012, benthic biodiversity noticeably increased in 2013–2016 to higher than the average of the area, indicating that dredging could improve the quality of benthic habitats and increase benthic biodiversity in sea areas with heavy sedimentation and pollution.