Pollution status and indicators in mangrovedominated estuaries of the Eastern Cape, South Africa

Abstract

Mangrove-dominated estuaries are important coastal resources, essential to our global socioeconomic growth. These multilayered unparalleled ecosystems are, however, among the most threatened in the world, particularly when they occur in urban matrices. Given the complex pollutant-environment-organism interactions in mangroves, as well as the dearth of baseline data on pollutant levels, monitoring the fate and distribution of pollutants, particularly microplastics (MP) and elements (heavy metals, trace metals and major elements) in these ecosystems is challenging, especially in developing countries like South Africa. Furthermore, there are presently limited studies using appropriate bioindicators for assessing the impact of pollutants, in both polluted and unpolluted mangrove areas. This motivated the present study which aimed to characterize MP and elemental pollutant statuses and identify indicators of MP pollution in the mangrove-dominated estuaries along the east coast of South Africa, in relation to disturbances acting on them. Furthermore, various indices were applied to assess the potential adverse impacts of metals and MPs in the ecosystems investigated. These mangrove-dominated estuaries included the Nahoon Estuary (located in an urban matrix), Nxaxo, Mngazana, Ntafufu estuaries (all regarded as peri-urban) from the Eastern Cape and Durban Bay (located in an urban matrix) from KwaZulu-Natal (KZN).