Review: Kuffner IB, Walters LJ, Becerro MA, Paul VJ, Ritson-Williams R, Beach KS (2006). Inhibition of coral recruitment by macroalgae and cyanobacteria. Marine Ecology Progress Series, 323:107-117.

Feature Paper: Kuffner IB, Walters LJ, Becerro MA, Paul VJ, Ritson-Williams R, Beach KS (2006). Inhibition of coral recruitment by macroalgae and cyanobacteria. Marine Ecology Progress Series, 323:107-117.

Author Abstract: Coral recruitment is a key process in the maintenance and recovery of coral reef ecosystems. While intense competition between coral and algae is often assumed on reefs that have undergone phase shifts from coral to algal dominance, data examining the competitive interactions involved, particularly during the larval and immediate post-settlement stage, are scarce. Using a series of field and outdoor seawater table experiments, we tested the hypothesis that common species of macroalgae and cyanobacteria inhibit coral recruitment. We examined the effects of Lyngbya spp., Dictyota spp., Lobophora variegata (J. V. Lamouroux) Womersley, and Chondrophycus poiteaui (J. V. Lamouroux) Nam (formerly Laurencia poiteaui) on the recruitment success of Porites astreoides larvae. All species but C. poiteaui caused either recruitment inhibition or avoidance behavior in P. astreoides larvae, while L. confervoides and D. menstrualis significantly increased mortality rates of P. astreoides recruits. We also tested the effect of some of these macrophytes on larvae of the gorgonian octocoral Briareum asbestinum. Exposure to Lyngbya majuscula reduced survival and recruitment in the octocoral larvae. Our results provide evidence that algae and cyanobacteria use tactics beyond space occupation to inhibit coral recruitment. On reefs experiencing phase shifts or temporary algal blooms, the restocking of adult coral populations may be slowed due to recruitment inhibition, thereby perpetuating reduced coral cover and limiting coral community recovery.


Note to Readers: Follow links above for author email, full article text, or the publishing scientific journal. Author notes in my review are in quotes.


Review: There are basically three areas of main research: 1) Laboratory work (either of a chemical / biochemical nature; computer modeling; mapping and other analyses-intensive research); 2) Field work; and 3) Experimentation and observation. This paper falls into the last classic methodology of science: experimentation. 

Last week we discussed the ability of reef-building hard corals to survive decalcification of their skeletons, which is a threat that may occur as greenhouse gas concentrations continue to rise in the atmosphere through human activities and burning of fossil fuels. That would be a catastrophic destruction of reefs as we know them, though some coral species would likely survive (as last week's paper showed).


A quicker destruction of reefs occurs when various elements are out of sync with optimal conditions for healthy reefs, and through this imbalance algae often gain the advantage (through growing faster than corals) and can overgrow and kill corals, leading to a phase shift (mentioned a few weeks ago)
This paper is important because it set out to show experimentally how algae and cyanobacteria can impede the successful recruitment of coral larvae (the hard coral Porites asteroides and the gorgonian Briareum asbestinum). This paper provides solid proof that "macrophytes affect coral recruitment," at least for the species of corals tested. This paper also showed that without a suitable substrate, coral recruits would die when in contact with algae and cyanobacteria.

The take-home message is that algae and cyanobacteria can produce chemicals and otherwise irritate the recruitment success of tested coral species.


It has been known for some time that coral larvae prefer to settle on crustose coralline algae (CCA) and it may be for the reason that other algae are deterrents. As CCA is an important cement on coral reefs and absorbs perhaps as much carbon dioxide as reef building corals, coral larvae may have evolved to seek out noncompetitive substrates where they can grow relatively unimpeded until they are large enough to overshadow small filamentous algae like those researched in this paper.


In the scientists' words, "We have presented evidence that locally common species of algae and cyanobacteria deter coral larvae from recruiting nearby despite the availability of suitable settlement substrate; most of the species we tested affected the location of coral recruitment."


Ilsa Kuffner and her team and collaborators are very good at putting out clear, concise experimental marine science papers aimed at provided proof of general concessions in the international marine science community. I highly recommend all her papers, and we'll continue with another study of hers, also about increased carbon dioxide concentrations in the ocean, like the last paper.