Skeletal growth of four scleractinian corals is not enhanced by in situ mesozooplankton enrichment.
Marine Ecology-Progress Series
The abundance of naturally occurring mesozooplankton (> 200 μm in width) was enriched in situ nightly for one month around transplanted fragments of four coral species (Pocillopora verrucosa, Acropora nasuta, Porites rus, and Montipora sp.) in a clear, shallow lagoon on the north shore of Moorea, French Polynesia, to determine if increased zooplankton availability enhanced coral skeletal growth. Zooplankton were attracted throughout each night to the corals using light from gallium nitride LED emitters tuned to one of four wavelengths [590 nm (Amber), 525 nm (Green), 470 nm (Blue), 400 nm (Near Ultraviolet)] and an unlit control. Mean total zooplankton abundance and biomass were significantly enriched above ambient concentrations surrounding the coral transplants by a factor of 3 to14 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 supporting the hypothesis that skeletal growth of healthy corals living in shallow, light replete habitats may be adapted for greater reliance on autotrophy and that the ambient flux of zooplankton is sufficient to meet heterotrophic needs of the coral species investigated.