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Coral reefs are shifting from coral to algal-dominated ecosystems worldwide. Recently, Turbinaria ornata, a marine alga native to coral reefs of the South Pacific, has spread in both range and habitat usage. Given dense stands of T. ornata can function as an alternative stable state on coral reefs, it is imperative to understand the factors that underlie its success. We tested the hypothesis that T. ornata demonstrates ontogenetic variation in allocation to anti-herbivore defense, specifically that blade toughness varied nonlinearly with thallus size. We quantified the relationship between T. ornata blade toughness and thallus size for individual thalli within algal stands (N=345) on 7 fringing reefs along the north shore of Moorea, French Polynesia. We found that blade toughness was greatest at intermediate sizes that typically form canopies, with overall reduced toughness in both smaller individuals that refuge within the understory and older reproductive individuals that ultimately detach and form floating rafts. We posit this variation in blade toughness reduces herbivory on the thalli that are most exposed to herbivores and may facilitate reproduction in dispersing stages, both of which may aid the proliferation of T. ornata.
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Corallivory on small Porites colonies increases with coral colony size but is reduced by macroalgal associational refuge
Abstract Numerous tropical macroalgae provide associational refuge to other benthic organisms, presumably due to their physical structure and/or production of chemical metabolites. One feature determining their effectiveness as an associational refuge is likely to be the size of the organism benefitting from the refuge. Using a manipulative experiment in the back reef of Moorea, French Polynesia, we tested if the macroalgaTurbinaria ornataprovided an associational refuge from fish corallivores for small colonies of massivePoritesspp., and how this differed with colony size (20–100 mm diameter). Tissue loss through corallivory increased with colony size but was ~ 72% less forPoritescolonies associated withT. ornataversus colonies separated from this macroalga, while dense macroalgae beds on contemporary reefs negatively impact the recruitment, growth and survival of corals, small colonies ofPoritesappear to benefit, through reduced corallivory, by associating with the macroalgaTurbinaria. This association may come at a cost (e.g., reduced growth) and should be the focus of future research.
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- Award ID(s):
- 2224354
- PAR ID:
- 10465046
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Coral Reefs
- Volume:
- 42
- Issue:
- 6
- ISSN:
- 0722-4028
- Format(s):
- Medium: X Size: p. 1233-1237
- Size(s):
- p. 1233-1237
- Sponsoring Org:
- National Science Foundation
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