Changes in growth, internode distance and nutrient concentrations of the seagrass Halophila ovalis with exposure to sediment sulphide

Abstract

Sulphide concentrations in estuarine sediments are likely to increase with increased organic matter fluxes (eutrophication) and increased temperatures (global warming). The short-term effects of sulphide on the growth, nutrition and morphology of the seagrass Halophila ovalis (R.Br.) Hook. f. were investigated in situ. Sediments within a H. ovalis meadow were enriched with Na2S equivalent to 0, 1.1 and 4.2 g m-2. Sulphide diffusion tubes were estimated to increase sulphide concentrations by 1 to 4 mmol l-1, concentrations typical of elevated sulphide measured in natural systems. Biomass, internode distance and growth rate (mg apex -1 day-1) were determined, and plant material was analysed for soluble carbohydrate, carbon, nitrogen and phosphorus. Sulphide exposure caused significant reduction in growth (63%), average leaf weight (30%) and internode distance (15%). Above-ground tissue phosphorus concentration and internode distance were significant predictors of growth (R2 = 0.63, p < 0.01). These results demonstrate the plasticity of H. ovalis in response to a short-term sulphide pulse, and may have implications for recovery from transient sulphide stress. © Inter-Research 2008.