Microbial photosynthesis in coral reef sediments (Heron Reef, Australia)

Ursula Werner*, Anna Blazejak, Paul Bird, Gabriele Eickert, Raphaela Schoon, Raeid M.M. Abed, Andrew Bissett, Dirk de Beer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


We investigated microphytobenthic photosynthesis at four stations in the coral reef sediments at Heron Reef, Australia. The microphytobenthos was dominated by diatoms, dinoflagellates and cyanobacteria, as indicated by biomarker pigment analysis. Conspicuous algae firmly attached to the sand grains (ca. 100 μm in diameter, surrounded by a hard transparent wall) were rich in peridinin, a marker pigment for dinoflagellates, but also showed a high diversity based on cyanobacterial 16S rDNA gene sequence analysis. Specimens of these algae that were buried below the photic zone exhibited an unexpected stimulation of respiration by light, resulting in an increase of local oxygen concentrations upon darkening. Net photosynthesis of the sediments varied between 1.9 and 8.5 mmol O2 m-2 h-1 and was strongly correlated with Chl a content, which lay between 31 and 84 mg m-2. An estimate based on our spatially limited dataset indicates that the microphytobenthic production for the entire reef is in the order of magnitude of the production estimated for corals. Photosynthesis stimulated calcification at all investigated sites (0.2-1.0 mmol Ca2+ m-2 h-1). The sediments of at least three stations were net calcifying. Sedimentary N2-fixation rates (measured by acetylene reduction assays at two sites) ranged between 0.9 to 3.9 mmol N2 m-2 h-1 and were highest in the light, indicating the importance of heterocystous cyanobacteria. In coral fingers no N2-fixation was measurable, which stresses the importance of the sediment compartment for reef nitrogen cycling.

Original languageEnglish
Pages (from-to)876-888
Number of pages13
JournalEstuarine, Coastal and Shelf Science
Issue number4
Publication statusPublished - Mar 1 2008
Externally publishedYes


  • Australia
  • Heron Island
  • N-fixation
  • calcification
  • coral reefs
  • light-dark shift method
  • microphytobenthic photosynthesis
  • permeable sediments

ASJC Scopus subject areas

  • Oceanography
  • Aquatic Science


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