ENDOLITHIC MICROFLORA ARE MAJOR PRIMARY PRODUCERS IN DEAD CARBONATE SUBSTRATES OF HAWAIIAN CORAL REEFS¹

Abstract

To quantify the contribution of endolithic phototrophs to primary production of dead carbonate substrates, experimental blocks of cleaned Porites lobata Dana skeleton were placed at three different sites in Kaneohe Bay, Hawaii: inshore, lagoonal, and oceanic. After 6 months of exposure, experimental blocks were colonized by communities characteristic of their estuarine (inshore, lagoonal) and oceanic (ocean) environments. Blocks were subsampled; net photosynthesis (NP) and chl a concentrations of the whole blocks (epi-and endoliths) and scrapped blocks (only endoliths) were quantified. Green turf algae colonized predominantly inshore and lagoonal blocks, while encrusting corallines were the dominant epiliths colonizing oceanic blocks. Four main species of endolithic phototrophs were identified in all blocks: Mastigocoleus testarum Lagerheim, Plectonema terebrans Bornet and Flahault (cyanobacteria), Phaeophila dendroides Crouan and Crouan, and Ostreobium quekettii Bornet and Flahault (Chlorophytes). While epiliths were very different between sites, NP rates and chl a concentration of endoliths did not vary significantly and were positively correlated (191 AE 25 mmol C . m À 2 . day À 1 and 590 AE 150 mg chl a . m À 2 of reef, respectively). Assimilation numbers for whole communities, including both epilithic and endolithic communities, were similar to those measured for endolithic communities alone (average of 0.3 g C . g chl a . h À 1 ). Under experimental conditions, the contribution of endolithic phototrophs to community NP rates of blocks ranged from 56% to 81%, and under natural conditions, we estimated that this contribution ranged between 32% and 46%. Thus, we showed that the endolithic phototrophs are one of the major primary producers in dead coral substrates in a wide range of coral reef environments.

Light microclimate of endolithic phototrophs in the scleractinian corals Montipora monasteriata and Porites cylindrica

“…Endolithic phototrophs are not limited to living corals, and are primary inhabitants of dead corals and other dead carbonate substrates, where they can eventually become predominant due to their low light requirement and ability to penetrate deeper into the carbonate matrix of the skeleton (Chazottes et al 1995, Le Campion-Alsumard et al 1995, Tribollet et al 2006.…”

Bioerosion by euendoliths decreases in phosphate-enriched skeletons of living corals

“…In dead corals, euendoliths have been shown to be important primary producers, and major agents of reef bioerosion and sediment production (Schneider and Torunski, 1983;Chazottes et al, 1995;Perry, 2000;Tribollet et al, 2002Tribollet et al, , 2006Tribollet and Golubic, 2005). Various environmental…”

Stable isotopic records of bleaching and endolithic algae blooms in the skeleton of the boulder forming coral Montastraea faveolata

“…Entire communities of endolithic photoautotrophs (i.e., algae and cyanobacteria) can make up a large proportion of net primary productivity in heads of dead boulder forming corals (Tribollet et al 2006). Yet, when shaded by live coral tissue, endolithic algae receive less than 5% of ambient light (Rodriguez-Roman et al 2006) limiting their productivity to \4% that of coral symbionts (Shashar and Stambler 1992).…”