Influence of trace metals in recent benthic foraminifera distribution in the Pearl River Estuary

• We report the distributions of trace metals and benthic foraminiferal assemblages.
• Hydrodynamic conditions affect the transport of sediment and trace metals.
• Copper, Zn, and Pb determine the distribution patterns of foraminifera.
• Ammonia tepida is pollution tolerant to trace metals and organic carbon.

This work analyzed the distribution of trace metals and benthic foraminifera in the Pearl River Estuary and studied the influence of environmental parameters (i.e., trace metals, organic matter and sediment grain size) on the total (living plus dead) benthic foraminiferal assemblages. The results indicate that the distribution patterns of Co, Cr, Cu, Ni, Pb and Zn are strongly related to the behavior of the sedimentary clay fraction (kaolinite and illite) and are dispersed with sedimentary material, whereas Ba, Sr, V and Zr follow different trends. The study area is moderately to severely polluted with Co, Cr, Cu, Ni, Pb and Zn, and maximum values were found in the upstream and on the western side of the estuary, where the lowest levels of H(S), Fisher α index and number of species are situated. Analyses of species abundance and community diversity, as well as the subsequent canonical redundancy analysis, were conducted to reveal the relationship between the foraminifera data and environmental parameters. Two assemblages were established by cluster analysis and were distributed in relation to bathymetry. The distribution of foraminiferal assemblages was mainly determined by Cu, Zn and Pb; while sand may exert an influence on particular species. Ammonia tepida, Haplophragmoides canariensis and Elphidium nakanokawaense are tolerant to the metal enrichment; while the abundances of the other species decline and are prejudiced. This study indicates that benthic foraminifera can be used as a bio-indicator of trace metal pollutants in the Pearl River Estuary and the results promote a better understanding of the response of benthic foraminifera to human-induced pollution in estuaries.