Holbrook, S.J. and R.J. Schmitt. 2004. Population dynamics of a damselfish: effects of a competitor that also is an indirect mutualist. Ecology 85:979-985.
Holbrook, S.J., A.J. Brooks, R.J. Schmitt and H.L. Stewart. 2008. Effects of sheltering fish on growth of their coral hosts. Marine Biology 155: 521-530.
Holbrook, S.J., R.J. Schmitt and A.J. Brooks. 2011. Indirect effects of species interactions on habitat provisioning. Oecologia in press.
The planktivorous damselfish, Yellow-tail Dascyllus (Dascyllus flavicaudus), feeding above their branching coral host, Pocillopora eydouxi. The fish shelter among the branches of their coral host when threatened by predators during the day and throughout the night. Skeletal growth of Pocillopora colonies increases with increasing number (biomass) of sheltering damselfish, which is related to increased concentrations of nitrogenous wastes that are excreted by fishes and taken up by the coral.
Field experiments by MCR investigators revealed that planktivorous damselfish greatly enhance the rate of coral skeletal growth (panel a) and increases in colony volume (panel b) of habitat-providing corals among whose branches the fish shelter. Short-term (1 mo) experiments done in 2005 (open circles) and 2008 (closed circles) indicated that the rate of coral calcification (skeletal growth) increased with increases in the number of fish individuals that sheltered on a colony. A long-term field experiment revealed that the annual increase in volume of a branching coral was twice as great when damselfish sheltered on it compared to colonies where damselfish were kept away (data are mean ± 1 SE; treatments are statistically different at P < 0.05). Ammonium concentrations near coral branches were greatly enriched when damselfish were present on a coral (data not shown), and the ammonium excreted was incorporated into the tissues of the coral, which appeared to fuel photosynthesis by the coral's endosymbionts (Symbiodinium).
Modified from Holbrook et al. 2011.