Historical eutrophication and pollution records off Bandar Abbas coast (North of Strait of Hormuz) using benthic foraminiferal ecology and geochemistry of trace elements from a sediment core

Abstract

Magnetic susceptibility, major and trace element concentration, as well as the foraminiferal assemblage in a radiocarbon-dated sediment core from the coastal area of Bandar Abbas city, were analysed to assess the source and degree of pollution during the urbanization period and compare it with the pre-urbanization natural environment. The measured background concentration of the elements in the area (except Mn, As, Cd, Mo and U) fell into the intermediate range between background in global limestone and earth crust. During the last five centuries, any natural induced considerable change in the sedimentation rate or sediment texture and composition of the study area has not taken place. Even so, a slight rise in sand content and a much more increase in magnetic susceptibility values occurred during the recent decades (recorded in the top 20 cm of the core). Moreover, at the same time, trace metal concentrations, especially Mo, Cd, Cu and U in the core sediment increased dramatically, which can be attributed to high organic matter influx. Study of benthic foraminiferal ecology demonstrated an increase in the proportion of hypoxia-tolerant hyaline as well as abnormal taxa and a corresponding decrease in hypoxia-intolerant porcelaneous species during recent decades.