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

Sulphide concentrations in estuarine sediments are likely to increase with increasedorganic matter fluxes (eutrophication) and increased temperatures (global warming). The short-termeffects 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 Na2Sequivalent to 0, 1.1 and 4.2 g m–2. Sulphide diffusion tubes were estimated to increase sulphide concentrationsby 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 plantmaterial was analysed for soluble carbohydrate, carbon, nitrogen and phosphorus. Sulphide exposurecaused significant reduction in growth (63%), average leaf weight (30%) and internode distance(15%). Above-ground tissue phosphorus concentration and internode distance were significant predictorsof growth (R2 = 0.63, p <0.01). These results demonstrate the plasticity of H. ovalis in responseto a short-term sulphide pulse, and may have implications for recovery from transient sulphide stress.