Spatial and temporal distribution of macrobenthic fauna of subtropical Richards Bay Harbour, South Africa

Abstract

Richards Bay Harbour, which was constructed in early 1976, is South Africa’s largest and busiest port. Despite comprising mostly deep channels (>15 m) and associated harbour and shipping activities, the system still functions as an estuarine system. Information on the macrozoobenthic community structure in Richards Bay Harbour is scarce. This study was therefore conducted to examine the status of the macrobenthic community structure. Sediment and benthic samples were collected quarterly using a Van Veen grab during the period 2016–2017. The majority of habitat types had sediment compositions ranging from very fine sand to mud. The implication of this difference in sediment substrata was profound in the benthic abundance and distribution. Analyses of the benthic fauna identified 98 taxa, of which the tanaid Halmyrapseudes digitalis, the polychaetes Mediomastus capensis, Aphelochaeta marioni and Prionospio sexoculata and the brachyuran crab Paratylodiplax blephariskios were numerically abundant. Multivariate analyses performed using PRIMER and PERMANOVA indicated significant differences in community structure between sites and habitat types, with no significant differences between seasons. The intertidal mudflat areas in Richards Bay Harbour supported a more diverse assemblage, with habitat types strongly influencing the community structure. Despite this, habitat loss and degradation due to anthropogenic pressure from harbour and industrial activities were identified as potential threats to the overall abundance and distribution of macrozoobenthic organisms in Richards Bay Harbour. We conclude that despite anthropogenic pressures related to industrial and port activities, Richards Bay Harbour still contains estuarine habitat of high conservation importance that supports a diverse macrobenthic community.