MEPS 489:143-153 (2013)  -  DOI: https://doi.org/10.3354/meps10422

ABSTRACT: The importance of heterotrophy in enhancing the skeletal growth of corals in transparent, shallow tropical waters is unclear. The impact of food availability on coral growth was examined by enriching the abundance of naturally occurring mesozooplankton (>200 µm in width) in situ nightly for 1 mo around transplanted fragments of 4 coral species (Pocillopora verrucosa, Acropora nasuta, Porites rus, Montipora sp.) in a lagoon of Moorea, French Polynesia. Zooplankton were attracted to the corals throughout each night using light from gallium nitride light-emitting diodes tuned to 1 of 4 wavelengths (590 nm [amber], 525 nm [green], 470 nm [blue], 400 nm [near UV, hereafter called violet]). An unlit light source was used as control. Mean total zooplankton abundance and biomass were significantly enriched above ambient concentrations by a factor of 3 to 14 times under green, blue, and violet wavelengths; amber did not enrich abundance or biomass. The mean abundance of specific taxa known to be favored for ingestion by corals (e.g. amphipods, mysids, polychaetes, crustacean larvae) was significantly enriched by as much as 100-fold. Despite sustained increases in the availability of mesozooplankton, none of the 4 coral species experienced higher skeletal growth under zooplankton enrichment compared to those exposed to ambient zooplankton concentrations. This pattern supports the conclusion that skeletal growth of healthy corals living in shallow, light-replete habitats may be adapted for greater reliance on autotrophy. The low ambient flux of zooplankton appears sufficient to meet the heterotrophic needs of the coral species investigated.

KEY WORDS: Coral skeletal growth · Mesozooplankton · Coral feeding · Zooplankton enrichment · Coral heterotrophy