Heavy Metal Contamination in Coastal Sediments and Its Impact on Aquatic Biodiversity: Sources, Ecological Risks, and Sustainable Management Strategies

Abstract

The persistence, toxicity and environmental effects of heavy metals have become a very important environmental issue in the coastal sediments. The sources of heavy metals which are found in the industrial effluents, mining, agricultural run-offs, urbanization, shipping and the waste water effluents also gather along the coast and forms sink in the sediments. These metals may be remobilized to the aquatic environment under different environmental conditions and thus of significance to the aquatic organisms. The purpose of this review is to bring together all the available information based on distribution, sources, environmental fate, ecological impacts and risk evaluation of heavy metals in coastal sediments i.e. the impact of heavy metals on aquatic biodiversity. Adverse impacts of cadmium, lead, mercury, arsenic, chromium, copper, zinc and nickel on microorganisms, phytoplankton, benthic invertebrates, fish, mangroves, seagrasses and coral reef systems are pointed out. The ecologic and human health hazards are further enhanced by aquatic food chains by bioaccumulation and biomagnification. The most popular ecological risk assessment tools (Geoaccumulation Index, Enrichment Factor, Pollution Load Index, Potential Ecological Risk Index and Sediment Quality Guidelines), and existing remediation and sustainable management plans are considered. Review also reveals critical research gaps like interaction of climate change, molecular and geospatial technologies to monitor the environment and the role of synergy of a combination of pollutants. Thus, the improvement of the integrated coastal management and long-term monitoring programs will be important to protect and to sustainably manage the aquatic biodiversity and coastal ecosystems.