Effects of sulfide concentration, pH, and anoxia on photosynthesis and respiration of Zostera marina

Abstract

ABSTRACT. Sulfide produced in marine sediments by sulfate reduction is toxic for several macrophytes, and high sediment sulfide concentrations have been associated with seagrass die-off events. Sulfide has been shown to reduce growth in a number of seagrasses, but little is known about its effect on the photosynthetic and respiratory metabolism. Consequently, the aim of this research was to evaluate the effect of sulfide on photosynthesis and respiration of the seagrass Zostera marina. Photosynthetic oxygen evolution and respiration were determined polarographically, while the optimum quantum yield was used as a measure of the photosynthetic performance of photosystem II in the leaves of Z. marina. The results showed that sulfide concentrations of approximately 1000 M could be considered an upper threshold limit for the survival of Z. marina in the coastal lagoons of Baja California (Mexico) studied. Respiration was not inhibited by sulfide concentrations up to 1000 M during 48-h incubations, while photosynthetic performance was reduced by short exposure to sulfide concentrations of 25 M but also by long exposure to concentrations as low as 50 M. This is the first study that shows that the photosynthetic capacity of Z. marina is not recovered once the sulfide-free conditions have been re-established.Key words: aerobic respiration, optimum quantum yield, sulfide, photosynthesis, Zostera marina. RESUMEN.El sulfuro producido en los sedimentos a consecuencia de la reducción del sulfato es tóxico para algunas macrófitas. De la misma manera, altas concentraciones de sulfuro en el sedimento han sido asociadas con eventos de mortalidad en pastos marinos. Se ha observado que la presencia de sulfuro reduce el crecimiento en algunos pastos marinos; sin embargo, el efecto sobre el metabolismo fotosintético y respiratorio es poco conocido. En consecuencia, el objetivo de esta investigación fue evaluar el efecto de sulfuro sobre la fotosíntesis y la respiración de la fanerógama marina Zostera marina. La evolución del oxígeno fotosintético y la respiración fueron determinados polarográficamente, en tanto que el rendimiento cuántico óptimo fue utilizado como una medida del desempeño fotosintético del fotosistema II en las hojas de Z. marina. Los resultados mostraron que las concentraciones de sulfuro cercanas a 1000 M pueden ser consideradas como el límite superior para la supervivencia de Z. marina en las lagunas costeras de Baja California (México) consideradas en este estudio. La respiración no presentó inhibición cuando las plantas fueron expuestas a concentraciones de sulfuro de 1000 M durante incubaciones de 48 h, mientras que el desempeño fotosintético disminuyó al ser expuestas a concentraciones de 25 M por cortos periodos de tiempo, pero también a exposiciones prolongadas en concentraciones de tan solo 50 M. Este es el primer estudio que muestra que la capacidad fotosintética de Z. marina no se recupera una vez que las condiciones libres de sulfuro son restablecidas.Palabras clave: respiración aeróbica, rendimi...

Nitrogen Uptake and Internal Recycling in Zostera marina Exposed to Oyster Farming: Eelgrass Potential as a Natural Biofilter

“…mussels) can lead to adverse effects on eelgrass performance due to the decrease in light availability by increasing leaf epiphyte cover and increased sulfide toxicity Korhonen et al 2012). As reported by Korhonen et al (2012), we observed that eelgrass beds were almost absent only directly under the oyster structures; this may indicate that shoots at the oyster site (i.e. 1-4 m near oyster longlines) were not directly exposed to the negative effects of oysters (e.g.…”

Sulfide intrusion in seagrasses assessed by stable sulfur isotopes—a synthesis of current results

“…However, if both detoxification capacities are exceeded and sulfide intrudes into active tissues such as the meristem, then the performance of the seagrasses is negatively affected (Borum et al, 2005;Garcias-Bonet et al, 2008;Pulido and Borum, 2010;Korhonen et al, 2012). Negative effects of sedimentary sulfide can thus be expected when the reoxidation capacity of the plants is inhibited by environmental or biological stress.…”

Sustainable Seagrass Restoration in the Virginia Coastal Bays

“…The electron transport rate (ETR) declined throughout the experimental period in both light and dark treatments for each sediment type ( In previous experiments, sulfide concentrations over 25 μM have been found to cause a decline in optimum quantum yield (F v /F m ) over short (1.5 hour) incubation periods with an upper threshold for Z. marina survival at 1000 μM (Korhonen et al 2012). Dooley et al (2013) found that Z. marina seedlings were killed at concentrations of H 2 S above 680 μM.…”