Heterotrophy in corals: zooplankton predation by the hydrocoral Millepora complanata

Abstract

Heterotrophy is examined in the hydrocoral Millepora complanata Lamarck and compared with scleractinian corals. Natural zooplankton catch rates and digestion rates were determined from counts of prey items captured by the gastrozooids on surfaces of millepore colonies collected in the field. The mean catch rate or feeding rate (+ SD) was 7.1 ? 4.10 prey items cm-2 surface d-' and complete digestion of prey required about 24 h. Copepods comprised the bulk (63 %) of the diet. Based on the argument that measured catch rates of corals are highly variable because of plankton patchiness, and the assumption that millepore colonies with expanded zooids feed both day and night, a potential feeding or catch rate was derived from the mean number of gastrozooids on the colonies times the digestion rate. Daily food consumption estimated from the potential catch rates exceeded estimates of daily energy needed for respiration by a factor of 6.7. It was concluded that heterotrophic feeding in M. complanata can potentially supply more than the daily energy requirements of the hydrocoral and may exceed feeding rates of scleractinian corals.

Effect of naturally changing zooplankton concentrations on feeding rates of two coral species in the Eastern Pacific

“…In addition to fixed carbon, zooplankton are thought to provide corals with nutrients such as nitrogen and phosphorus that are not supplied by zooxanthellae (Muscatine and Porter, 1977;Szmant-Froelich and Pilson, 1980;Lewis, 1992;Risk et al, 1994;Titlyanov et al, 2000;Fitt and Cook, 2001;Titlyanov et al, 2001). It is believed that heterotrophic inputs are necessary for maximal coral growth (Wellington, 1982;Miller, 1995;Houlbrèque et al, 2003), with isotopic evidence indicating that as much as 66% of the fixed carbon in coral skeletons can come from these inputs (Grottoli and Wellington, 1999).…”

“…Ingestion rates are better understood on other coelenterates such as anemonies and hydroids (e.g. Lasker, 1981;Sebens and Koehl, 1984;Lewis, 1992;Coma et al, 1994;Ribes et al, 1998;Lin et al, 2002), for which annual variations in feeding rates have been investigated (Ribes et al, 1999).…”

Effect of feeding on the carbon and oxygen isotopic composition in the tissues and skeleton of the zooxanthellate coral Stylophora pistillata

“…They are able to fix inorganic carbon through the photosynthetic activity of their dinoflagellate symbionts, the zooxanthellae (Rahav et al 1989, Muscatine 1990). They may also derive a fraction of their energy either through predation on bacterioplankton (Farrant et al 1987, Sorokin 1991, Ferrier-Pagès et al 1998) and zooplankton (Sorokin 1991, Lewis 1992, Sebens et al 1996 or through the use of dissolved organic matter (Sorokin 1973, AlMoghrabi et al 1993. Such heterotrophic nutrition was suggested to be predominant in deep waters, where rates of photosynthesis are low (Muscatine et al 1989, Anthony & Fabricius 2000.…”

Importance of a micro-diet for scleractinian corals

“…Heterotrophy is important for most corals (Sebens et al 1996, Houlbrèque et al 2003; it is primarily a source of nitrogen, phosphorus and amino acids not supplied via symbiont photosynthesis (Muscatine & Porter 1977), which mostly brings carbon-rich compounds to the animal (Sebens 1987, Lewis 1992, Cook et al 1994, Risk et al 1994. Heterotrophy can, therefore, be an important source of energy depending on the environmental conditions, since it may bring more than 60% of the total energy to corals living in deep waters or in shaded environments (Falkowski et al 1984).…”