A review of microalgae as indicators in South African estuaries

Microalgae are one of the most important components of estuarine ecosystems, providing the fuel required to sustain higher trophic levels. Being at the base of aquatic food webs, these communities are generally the first to respond to anthropogenic disturbances - particularly opportunistic species - and can often be used effectively as indicators of ecosystem health. The purpose of this review is to assess the status of estuarine microalgal research in South Africa and to highlight the shortcomings of past research and identify priorities for future research. What became apparent during a synthesis of South African literature on the topic, was that the broad ecology of microalgae - both phytoplankton and microphytobenthos - has been well addressed. Generally speaking, the interaction between freshwater inflow and microalgal communities has formed the basis for the majority of this research. This trend was logical due to South Africa being a relatively arid country, where demand for freshwater often exceeds supply. In terms of microalgal studies however, numerous shortcomings can be identified, including the lack of: (1) thorough assessments of microalgal community composition; (2) conclusive demonstration of the role of suggested indicator species; (3) adequate sampling periods and/or intensity; and (4) fine -scale experimental research - both in situ and laboratory. A concern on a broader scale, and in stark contrast to Europe and the United States, is the lack of explicit assessment of what comprises eutrophication in South African estuaries. Finally, and perhaps the most pertinent theme identified in this review is the necessity for adopting 'hypothesis -driven research'. (C) 2016 SAAB. Published by Elsevier B.V. All rights reserved.