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 Na 2 S 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 (R 2 = 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.

Harmful algae are not harmful to everyone

“…1A), a likely common phenomenon (Martinez-Luscher and Holmer, 2010;Hoeffle et al, 2011;Holmer et al, 2011). Sulphide is an enzyme inhibitor and therefore a phytotoxin, and high porewater sulphide levels have previously been shown to reduce seagrass growth (Koch et al, 2007;Kilminster et al, 2008). Thus, a combination of light reduction (Hauxwell et al, 2003;Brun et al, 2008), competition for nutrients (Hughes et al, 2004;Burkepile and Hay, 2006) and accumulation of sulphides in the sediment (Koch and Erskine, 2001;Holmer et al, 2005;Koch et al, 2007) are likely mechanisms whereby G. comosa reduces the abundance of H. ovalis.…”

Species-Specific Trait Responses of Three Tropical Seagrasses to Multiple Stressors: The Case of Increasing Temperature and Nutrient Enrichment

“…The decrease in BG growth is a common strategy in seagrasses plants to adjust their productivity to environmental resources ( Alcoverro et al, 2001 ). Shorter IL, as a proxy of higher shoot and root density, is a common feature under stressful environmental factors, suggesting that H. stipulacea invests excess energy (increased Alpha values) in increasing number of shoots ( Jensen and Bell, 2001 ; Kilminster et al, 2008 ) rather than on leaf length. In the literature, H. stipulacea thermal optima and limits showed differences between populations ( Nguyen et al, 2020 ; Wesselmann et al, 2020 ) but thermal optima at the Red Sea was set at 30°C ( Anton et al, 2020 ; Wesselmann et al, 2020 ).…”

Optimum Temperatures for Net Primary Productivity of Three Tropical Seagrass Species

“…Using the spreadsheet in Supplement 2 , the change in net plant productivity can be estimated for any given rise in water temperature. It is important to note, however, that rises in water temperature could increase vulnerability to other stressors including light limitation (Collier et al, 2016 ), contaminants (Wilkinson et al, 2017 ), disease susceptibility (Kaldy, 2014 ), and sulfide intrusion (Koch et al, 2007 ; Kilminster et al, 2008 ).…”