The benthic regeneration of N and P in the Great Brak estuary, South Africa

Authors

  • Lucienne RD Human Nelson Mandela Metropolitan University, Summerstrand South Campus, Department of Botany, PO Box 77000, Port Elizabeth 6031, South Africa
  • Gavin C Snow School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa
  • Janine B Adams Nelson Mandela Metropolitan University, Summerstrand South Campus, Department of Botany, PO Box 77000, Port Elizabeth 6031, South Africa
  • Guy C Bate Nelson Mandela Metropolitan University, Summerstrand South Campus, Department of Botany, PO Box 77000, Port Elizabeth 6031, South Africa

DOI:

https://doi.org/10.4314/wsa.v41i5.02

Keywords:

water quality, nutrient cycling, benthic-pelagic coupling, estuary

Abstract

The Great Brak is a temporarily open/closed estuary (TOCE) located on the south coast of South Africa. The construction of the Wolwedans Dam in 1989 reduced baseflow to the estuary by 56%, decreasing the intensity of flushing events and causing the mouth to breach less often. The aim of this study was to investigate the flux of inorganic nutrients (NH4+, TOxN [NO3 + NO2], SRP) as well as total N and P across the sediment–water interface in the estuary. There have been very few studies on nutrient cycling and benthic pelagic coupling in South African estuaries. This study showed that the sediment had a net efflux of NH4+, SRP, TN and TP while TOxN was taken up or converted to other forms of N. The estuary acted as a source of N and P during both summer and winter. If the estuary remains closed for a prolonged period (12 months), with an increased organic load present on the benthos, the associated rates of efflux of N and P would increase. In order to reduce the organic load to the system better flushing methods or, more importantly, an increase in base flow, is needed to reduce residence times of water in the estuary.

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Published

2015-10-29

How to Cite

Lucienne RD Human, Gavin C Snow, Janine B Adams, & Guy C Bate. (2015). The benthic regeneration of N and P in the Great Brak estuary, South Africa. Water SA, 41(5 October). https://doi.org/10.4314/wsa.v41i5.02

Issue

Section

Research paper