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Marine Ecology Progress Series

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MEPS 492:111-123 (2013)  -  DOI:

Benthic macrofauna of an estuarine lake during a drought: spatio-temporal drivers under different hydrological states

Deena Pillay1, Renzo Perissinotto2,3

1Marine Research Institute, Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa
2School of Life Sciences, University of KwaZulu-Natal, Durban 4000, South Africa
3DST/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031, South Africa

ABSTRACT: Mouth state is a key determinant of estuarine processes in arid and semi-arid regions. While this factor is well researched for periodically open systems, it is much less researched for estuarine lakes. Here we used a 4-year data set to determine spatio-temporal patterns in responses of benthic macrofauna to changes in mouth state in a subtropical estuarine lake system during a drought cycle, with a focus on understanding the ecological mechanisms driving community change. We also assessed the effects of changes in mean levels of environmental factors relative to their statistical variability (measured as standard deviation, SD) in driving changes in species richness and abundance of dominant macrofauna. Results showed that greatest variability in physico-chemical factors and macrofaunal assemblages occurred in the upper lake sections, especially under closed mouth conditions. At the community level, changes in salinity under different mouth states played an important structuring role, but were less important at the level of individual species, being important for only 1 of the 6 dominant species. Low oxygen levels under closed mouth conditions, particularly in the lake complex, were also an important determinant of macrofaunal community structure and species richness. A major finding was that variability (SD) in environmental factors was more important in determining species richness and abundance of dominant macrofauna than changes in mean levels. This suggests that, while dominant species in the systems can tolerate significant environmental changes, the rate and magnitude of change exert an important control over species abundance. 

KEY WORDS: St Lucia Estuary · Benthos · Drought · Mouth dynamics · Environmental variability

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Cite this article as: Pillay D, Perissinotto R (2013) Benthic macrofauna of an estuarine lake during a drought: spatio-temporal drivers under different hydrological states. Mar Ecol Prog Ser 492:111-123.

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