Macrobenthic community structure of the Mhlathuze Estuary, a permanently open estuarine embayment in KwaZulu-Natal, South Africa

Abstract

The Mhlathuze Estuary, an estuarine embayment in northern Zululand, is considered an estuary of national conservation importance. No historical data on the benthic macrofauna are available for the past 20 years, creating a significant gap in our understanding of the ecology and benthic  assemblage of this system. The primary aim of this study was to provide updated information on the ecology of the macrobenthic community.  Benthic samples were collected quarterly using a Zabalocki grab during the period 2016–2017. The 87 taxa recorded were largely dominated by the tanaid Halmyrapseudes cooperi, followed by the brachyuran crab, Paratylodiplax blephariskios and the amphipod Grandidierella bonnieroides. A multivariate data analysis was performed and PERMANOVA results indicated significant differences (p < 0.05) between sites in number of taxa, species diversity and density. A stable system with limited seasonal influences and the effect of May 2017 flood were highlighted in the study. The
100 benthic taxa recorded in previous studies, of which 46 species are still present, suggests a marked decline in macrobenthic diversity and a  change in community, possibly linked to reduced freshwater inflow and agricultural effluent. The continuing ecological relevance of this protected area relies on reducing catchment activities that are detrimental in sustaining benthic populations.

Keywords: anthropogenic, assemblage, habitat, mudflat, mangrove, physico-chemical, sediment