The decomposition of estuarine macrophytes under different temperature regimes

Abstract

The Great Brak Estuary is a temporarily open/closed system situated along the warm temperate coast of the Western Cape, South Africa. The estuary is subject to a variety of anthropogenic impacts (e.g. freshwater abstraction and sewage discharge) that increases its susceptibility to prolonged periods of mouth closure, eutrophication, and ultimately the formation of macroalgal blooms. The aim of this study was to determine the decomposition characteristics of the most dominant submerged macrophyte and macroalgal species in the Great Brak Estuary. Laboratory experiments were conducted to determine the effect of different temperature regimes on the rate of decomposition of 3 macrophyte species and the extent of inorganic nutrients released. The results demonstrated that anaerobic decomposition of Zostera capensis , Ruppia cirrhosa , and Cladophora glomerata resulted in high levels of inorganic nutrient release over the 28-day study period. Ammonium (NH4+) was the dominant form of dissolved inorganic nitrogen (DIN) released during the decomposition process for all three species.

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