title: Dynamic photoinhibition exhibited by red coralline algae in the Red Sea.
abstract: BACKGROUND
  Red 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.
  
  
  RESULTS
  Minimum 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.
  
  
  CONCLUSIONS
  This 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.
authors.affiliation: Scottish Oceans Institute, University of St Andrews, St Andrews, UK. hb57@st-andrews.ac.uk.
authors.forename: Heidi L
authors.initials: HL
authors.lastname: Burdett
authors.forename: Victoria
authors.initials: V
authors.lastname: Keddie
authors.forename: Nicola
authors.initials: N
authors.lastname: MacArthur
authors.forename: Laurin
authors.initials: L
authors.lastname: McDowall
authors.forename: Jennifer
authors.initials: J
authors.lastname: McLeish
authors.forename: Eva
authors.initials: E
authors.lastname: Spielvogel
authors.forename: Angela D
authors.initials: AD
authors.lastname: Hatton
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Kamenos
mesh_terms: D000064:Acclimatization; D002940:Circadian Rhythm; D003624:Darkness; D005453:Fluorescence; D019156:Indian Ocean; D042541:Intracellular Space / Q000378:metabolism; D055668:Photochemical Processes; D010788:Photosynthesis; D010860:Pigments, Biological / Q000378:metabolism; D000461:Rhodophyta / Q000378:metabolism / Q000502:physiology*; D013452:Sulfonium Compounds / Q000378:metabolism
chemical_list: D010860:Pigments, Biological; D013452:Sulfonium Compounds; C068078:dimethylpropiothetin