Comparison of the mesozooplankton community structures of estuary remnants in the Richards Bay Harbour

Kent Lawrence, Hendrik Jerling

Coastal Research Unit of Zululand, University of Zululand

Presentation Topic

The original Richards Bay estuary was modified into a deepwater harbour where only remnants of the original estuarine system remain as modified canal systems. One canal (Bhizolo) is polluted by industrial effluent and the other estuary remnant (Mzingazi canal) does not receive the same levels of industrial pollutants. No studies have been done on the zooplankton communities of these two canals. The present study aimed to address this paucity of information by comparing between canals, and comparing the canals to the original system, environmental variables and water nutrients.

Mesozooplankton sampling took place monthly after dark for 12 months, from March 2011 to March 2012. In terms of salinity, the Bhizolo canal received greater volumes of freshwater, where the Mzingazi canal received greater seawater intrusion. Two estuarine calanoid copepods, namely Acartiella natalensis and Pseudodiaptomus stuhlmanni, as well as coastal marine paracalanids, were dominant and their densities varied greatly between canals. A. natalensis and paracalanids favoured the fresher Bhizolo canal, whereas P. stuhlmanni favoured the Mzingazi canal. The marine copepods, Oithona spp, were found throughout all the sites during the sampled period, but densities significantly higher were recorded in the Mzingazi canal making it the dominant taxa in that canal. Acartia spinicauda, an alien species, had been found penetrating these canals during winter only, with the highest densities recorded in the Mzingazi canal. This species occurs during winter when the dominant species have decreased in densities.

Presentation Topic

Comparison of the mesozooplankton community structures of estuary remnants in the Richards Bay Harbour

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