Biological responses to a resumption in river flow in a freshwater-deprived, permanently open Southern African estuary

Vorwerk, P.D. and Froneman, P.W. and Paterson, A.W. and Strydom, N.A. and Whitfield, A.K. (2008) Biological responses to a resumption in river flow in a freshwater-deprived, permanently open Southern African estuary. Water SA, 34 (5). pp. 597-604. ISSN 1816-7950

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Abstract

The Kariega Estuary is a freshwater-deprived system due to numerous impoundments in the catchment. This system has had little or no horizontal salinity gradient over the last 15 years, with hypersaline conditions sometimes predominating in the upper reaches. Following high rainfall events in the catchment during the spring of 2006, including a flood event (approximate 1:10 year) in August 2006, a series of riverine pulses entered the estuary and a horizontal salinity gradient was established. This study examined the influence of this freshwater pulse on four components of the biota within the estuary, namely the zooplankton, and larval, littoral and demersal fishes. The study demonstrated that in three of these components elevated densities were recorded following the riverine input, with only the littoral fishes retaining an almost constant density. In addition, changes in the relative contributions of the estuarine utilisation classes for all three fish groups examined indicated that freshwater input into these systems positively influences the abundances. This has significant implications for water managers as it demonstrates the importance of an Ecological Reserve (defined as ‘the water required to protect the aquatic ecosystems of the water resource’) for this system.

Item Type:Article
Uncontrolled Keywords:biotic response, freshwater pulse, river inflow, Kariega Estuary, Eastern Cape, South Africa
Subjects:Y Unknown > Subjects to be assigned
Divisions:Faculty > Faculty of Science > Zoology & Entomology
Research Institutes and Units > South African Institute for Aquatic Biodiversity (SAIAB)
ID Code:1295
Deposited By: Mrs Eileen Shepherd
Deposited On:01 Feb 2009
Last Modified:06 Jan 2012 16:20
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