Dynamic photoinhibition exhibited by red coralline algae in the red sea

Abstract

BackgroundRed coralline algae are critical components of tropical reef systems, and their success and development is, at least in part, dependent on photosynthesis. However, natural variability in the photosynthetic characteristics of red coralline algae is poorly understood. This study investigated diurnal variability in encrusting Porolithon sp. and free-living Lithophyllum kotschyanum. Measured parameters included: photosynthetic characteristics, pigment composition, thallus reflectance and intracellular concentrations of dimethylsulphoniopropionate (DMSP), an algal antioxidant that is derived from methionine, an indirect product of photosynthesis. L. kotschyanum thalli were characterised by a bleached topside and a pigmented underside.ResultsMinimum saturation intensity and intracellular DMSP concentrations in Porolithon sp. were characterised by significant diurnal patterns in response to the high-light regime. A smaller diurnal pattern in minimum saturation intensity in the topside of L. kotschyanum was also evident. The overall reflectance of the topside of L. kotschyanum also exhibited a diurnal pattern, becoming increasingly reflective with increasing ambient irradiance. The underside of L. kotschyanum, which is shaded from ambient light exposure, exhibited a much smaller diurnal variability.ConclusionsThis study highlights a number of dynamic photoinhibition strategies adopted by coralline algae, enabling them to tolerate, rather than be inhibited by, the naturally high irradiance of tropical reef systems; a factor that may become more important in the future under global change projections. In this context, this research has significant implications for tropical reef management planning and conservation monitoring, which, if natural variability is not taken into account, may become flawed. The information provided by this research may be used to inform future investigations into the contribution of coralline algae to reef accretion, ecosystem service provision and palaeoenvironmental reconstruction.

Exchange Dynamics Reveal Significant Accumulation of Dimethylated Sulfur by Mediterranean Benthic Communities

“…A consistent daytime increase in intracellular DMSP across all benthos types was observed, supporting the proposed antioxidative role for DMSP (and its breakdown products) in marine macrophytes (Rix et al, 2012;Burdett et al, 2014). However, day/night trends of dimethylated sulfur benthic flux across habitat types were less consistent, reflecting the increase in community complexity as one moves through ecological scales-intracellular DMSP concentrations were determined from the holobiont of individual organisms, whilst benthic exchange fluxes were determined at the ecosystem community level, i.e., integrating the interactive effect of multiple organisms and holobionts across multiple trophic levels.…”

Uncovering the volatile nature of tropical coastal marine ecosystems in a changing world

“…In perhaps the most comprehensive study to date involving corals, production of dimethylated sulphur compounds (DMS, DMSP and dimethyl sulphoxide; DMSO) were shown to increase under antioxidant stress caused by variations in temperature, light, salinity and air exposure (Deschaseaux et al ., ), with each sulphur species exhibiting different responses to each environmental cue. Similar responses have also been shown for other groups of reef organisms, for example an increase in DMSP has been shown in response to diel variation in water temperature and light in Red Sea coralline algae (Burdett et al ., ).…”

Light Absorption in Coralline Algae (Rhodophyta): A Morphological and Functional Approach to Understanding Species Distribution in a Coral Reef Lagoon

“…In coralline algae, however, the capacity of carbonate skeleton to enhance light absorption and photosynthetic performance remains unknown (see Payri et al, 2001;Burdett et al, 2014). Recently, Vásquez-Elizondo and Enríquez (2016) documented significant differences in the light absorption properties of three coralline species, before and after exposing the experimental organisms to heat-stress.…”

“…This broad taxonomic group is present in virtually every coastal ecosystem, from highly illuminated, intertidal regions to extremely light-limited habitats like rock crevices or depths of 250 m (Johansen, 1981;Littler et al, 1985;Payri et al, 2001;Burdett et al, 2014). The ecological significance of coralline algae varies from playing a fundamental role as ecosystem engineers of highly diverse communities (Foster, 2001;Steller et al, 2003) to being the preferred substrate for settlement of invertebrate larvae (Heyward and Negri, 1999;Williams et al, 2008).…”