Long-term change of summer benthic macroinvertebrates driven by multiple stresses in the Changjiang Estuary

Abstract Both human activities and climate change influence benthic macroinvertebrates in the Changjiang Estuary. We investigated long-term variations in benthic macroinvertebrates and related them to changes in depth, salinity, temperature, pH, and dissolved oxygen in bottom water off the Changjiang Estuary from 10 summer cruises during 2006–2021. The bi-monthly multivariate ENSO index and summer runoff rate of Changjiang were used to estimate the climate change during this period. The abundance and biomass of benthic macroinvertebrates increased significantly from 2006 to 2014 owing to a series of environmental protection measures. Intensive El Niño promoted diluted water discharge and hypoxia in summer in the Changjiang Estuary since 2015. We noted changes in the macrobenthic community following these events, including a dramatic decrease in abundance and biomass, alterations in dominant species, and a decline in benthic diversity. Canonical correspondence and redundancy analyses revealed that depth, salinity, and dissolved oxygen were the main factors influencing the distribution of benthic macroinvertebrates. Owing to the ubiquitous pressure caused by human activities and climate change in estuaries, we conclude that international cooperation is required to protect estuarine ecosystems under the scenario of global climate change.