One of the major changes that have occurred in reef keeping over the last 10 years has been the increase in the number of aquarists who feed their corals. There has been an explosion in the number of products designed to provide live foods, mainly phytoplankton, to the reef aquarium. For many years it was felt that reef tanks, and especially corals, did not need to be fed. This was predicated on the fact that many of the corals kept at that time, in the systems of that day, appeared to do just fine and to grow and even reproduce without much intervention by the aquarist. Many of the corals species available in the early 90’s were soft corals, zoanthids, mushroom anemones and/or LPS corals, often from lagoonal or nutrient enriched areas. SPS corals were available only in smaller numbers and limited diversity. Tanks of the day were not as well filtered as they are today and as a result, had higher levels of nitrogen and phosphorus than commonly found in today’s systems. While for the
most part this line of thinking as been modified (first with fish and now with corals), I still feel that corals can do well in aquariums without direct feedings, provided certain conditions are met. Obviously there is a mounting body of evidence on the role of feeding in corals, and the methods by which they acquire and use that food. This paper contributes to this growing library of information and raises several interesting lines of investigation as to the exact role of various factors in coral health, and their effect on tissue and skeletal growth.

It is well known that corals live in areas of comparatively low nutrient concentration (nitrogen, phosphorus, carbon), and the mechanisms of how corals are able to do so has been the focus of study for almost 100 years. It is now known that zooxanthellae translocate carbon rich compounds (i.e. sugars) to their coral hosts. In some cases, this alone can meet 100% of the carbon needs of the coral host. In shallow waters, nitrogen abundance of coral tissue (4-6%) suggests that zooplankton is not the main source of nitrogen, which mostly comes from recycled dissolved inorganic nitrogen (i.e. ammonia, nitrate). However, in lower light conditions (deeper water/high turbidity), only about 40% of the carbon needs can be met in corals such as Stylophora pistillata. The same holds true for nitrogen, where deeper water corals show a much stronger zooplankton “signature”, and as such feeding allows these corals to continue to grow. However, it is felt that zooxanthellate
photosynthates (i.e. sugars) are more like “junk food” in that they are deficient in nitrogen, phosphorus and amino acids. For this reason some researchers feel that corals may be nitrogen limited. It has also been shown that zooxanthellae can be carbon limited with respect to dissolved inorganic carbon (i.e. CO2), especially when photosynthesis rates (needs CO2) greatly exceed respiration rates (a source of CO2). External food sources would solve these limitations by providing nitrogen, phosphorus and carbon for corals. Feeding also increases respiration rates thereby producing more CO2 for photosynthesis and growth.

Corals can feed on a wide range of food types, depending on species and morphology. Sediments, bacteria, dissolved and particulate organic matter, and zooplankton are the main ones. However, how dependant the various corals are on these types of nutrition is still a matter of some uncertainty. Few studies have measured the ingestion rates of natural zooplankton and fewer still have looked at the effects of feeding on photosynthesis, tissue and skeletal growth. Some studies have shown that feeding increases zooxanthellae numbers and photosynthesis, but other studies could find no difference in the amount of translocated photosynthates between fed and starved corals. Some studies have shown no change in tissue or skeleton growth in fed corals, while other studies have shown an increase in both.

The goal of this paper was three-fold. First, the researchers wanted to determine if feeding influenced the tissue composition and growth and if this effect was light dependant. Secondly, if feeding does do this, then does it also affect the coral photosynthetic capacities? The last question they wanted to explore was if feeding had a direct effect on photosynthesis, does this process also enhance calcification rates, especially in terms of dark versus light calcification. It has been shown that light does indeed drive calcification with light versus dark calcification ratios of about 4.

To determine the answers to the above questions, coral fragments were subjected to 2, 5 and 9 week regimes of feeding (fed abundantly twice a week for one hour with wild zooplankton consisting of 94% copepods and copepod larvae under 10 microns (1120 +/-152/L) and twice a week for one hour with Artemia salina nauplii (2003 +/-104/L)) and starvation (fed Artemia once a week for one hour, 100 +/- 34/L), under three PAR levels, 80, 200 and 300 umol/m2/s. After each feeding a 100% water change was performed.

Results confirmed that feeding enhanced coral growth rate and increased both the dark and light calcification rates. These rates were 50-75% higher for the heavily fed corals versus the lightly fed corals. After five weeks, chlorophyll a concentrations were four to seven times higher and the amount of protein was significantly higher in heavily fed corals. Photosynthesis rates were also found to be two to ten times higher than in lightly fed corals. It took over two weeks of feedings before any significant increases could be seen in the above parameters. Fed corals in low light significantly increased their number of zooxanthellae and the chlorophyll content increased in response to the shading that occurs when so zooxanthellae multiply and cause self-shading problems. The same effect can be seen when nitrogen-enriched seawater is used to grow corals. Indeed, this is what we see in aquariums at the Waikiki Aquarium that receive nitrogen, phosphorus and carbon dioxide rich seawater
from the Aquarium’s well. Increased nitrogen levels due to feeding, also result in increased protein levels in the coral tissue due to the higher nitrogen content of the photosynthates translocated to the coral.

The increase in calcification rates is more difficult to explain since the relationship between calcification and photosynthesis is still poorly understood and topic of much debate in the scientific community. Calcification as it is understood today, involves the delivery of calcium and inorganic carbon and the removal of protons at the site of calcification in the coral, which consists of an organic matrix laid down by the coral at the tissue/skeleton interface. It may be that the higher level of coral respiration caused by feeding, provides more CO2, which is needed for calcification. It has been shown that up to 70% of the inorganic carbon needed for calcification comes from respired CO2 as opposed to bicarbonate from the water. This hypothesis remains to be investigated. Another possibility is that the removal of protons is an energy expending process and it may be that feeding provides more energy for calcification to occur. This may be indicated by the fact that the rates of
dark calcification were more enhanced than the rates of light calcification.

Finally, the quality if the organic matrix laid down by the coral at night may have been enhanced by the appearance of more amino acids, particularly aspartic acid, in the heavily fed corals as compared to the lightly fed corals.

This study used but a single coral species, one known for its wide depth and geographic distribution. It remains to be seen whether the results presented by the study are indicative of all corals or just this single species.

The implications for aquarists are clear; feeding can greatly enhance growth rates in corals, especially in situations of lower light levels, such as those often found in home aquaria. However, many home aquaria have nitrogen and phosphorus levels several times (10-100x) that of natural reefs, so it is possible that nitrogen at least, would be in abundance and not a problem. Other compounds, such as amino acids, pigments etc. are of course another matter.

As I mentioned in the October 2003 (http://www.advancedaquarist.com/2003/10/media) column, many aquarists today are spending large sums of money dumping in food mixtures of various forms of phytoplankton. While there is evidence that phytoplankton is ingested in large quantities by several types of soft corals, the evidence for their use by SPS and LPS stony corals is lacking. Most of the literature today states that if they feed on plankton, stony corals feed on zooplankton. If you wish to feed SPS corals then zooplankton (copepod nauplii, rotifers, shellfish larvae) or plankton substitutes of the proper size (e.g. Golden Pearls) would be the way to go. For LPS corals larger food sizes such as finely chopped shrimp would be best. As I said in the October 2003 column, the improvements that people see in stony corals because of phytoplankton feeding may be more indirect than direct by increasing nutrient levels in the water and/or fueling the growth of other organisms that produce planktonic larvae.

Interesting Citations from the Periodical Literature

The following are citations for some of the articles that might also be of interest to aquarists, which were published in the summer and fall of 2003.

Anemones

1. Hamada, K. and M. Nishihara. 2003. Internal brooding of clonal propagules by a sea anemone, Anthopleura sp. Invertebrate Biology 122(4):293-298.
2. Mobley, K.B. and D.F. Gleason. 2003. The effect of light and heterotrophy on carotenoids concentration in the Caribbean anemone Aiptasia pallida (Verrill). Marine Biology 143(4):629-635.

Cephalopods

1. Domingues, P., Sykes, A., Jommerfield, A., Almansa, E., Lorenzo, A. and J.P. Andrade. 2004. Growth and survival of cuttlefish ( Sepia officinalis ) of different ages fed crustaceans and fish. Aquaculture 229(1-4):239-254.

Corals

1. Latin American Coral Reefs. Ed. J. Cortes. Elsevier Science BV (Amsterdam) 2003, 497 pp, ISBN: 0-444-51388-4.
2. Castanaro, J. and H.R. Lasker. 2003. Colony growth responses of the Caribbean octocoral, Pseudopterogorgia elisabethae, to harvesting. Invertebrate Biology 122(4):299-307.
3. Dobretsov, S. and P.Y. Quinn. 2004. The role of epibiotic bacteria from the surface of the soft coral Dendronephthya sp. in the inhibition of larval settlement. Journal of Experimental Marine Biology and Ecology 299(1):35-50.
4. Grover, R., Maguer, J-F., Allemand, D. and C. Ferrier-Pages. 2003. Nitrate uptake in the scleractinian coral Stylophora pistillata. Limnology and Oceanography 48(6):2266-2274.
5. Idaji, J.A. and P.J. Edmunds. 2003. Free-living colonies of Porites in Moorea, French Polynesia. Bulletin of Marine Science 72(3):1025-1032.
6. Lasker, H.R., Boller, M.L., Castanaro, J. and J.A. Sanchez. 2003 Determined growth and modularity in a gorgonian octocoral. Biological Bulletin 205(3):319-330.
7. Levy, O. , Dubinsky, Z. and Y. Achituv. 2003. Photobehaviour of stony corals: responses to light spectra and intensity. Journal of Experimental Biology 206(22):4041-4050.
8. Meroz,-Fine, E., Brickner, I., Loya, Y. and M. Ilan. 2003. The hydrozoan coral Millepora dichotoma: speciation or phenotypic plasticity? Marine Biology 143(6):1175-1184.
9. Piniak, G.A., Lipschultz, F. and J. McClelland. 2003. Assimilation and partitioning of prey nitrogen within two anthozoans and their endosymbiotic zooxanthellae. Marine Ecology Progressive Series 262(03):125-136.
10. Reichelt-Brushett, A.J. and C. McOrist. 2003. Trace metals in living and non- living components of scleractinian corals. Marine Pollution Bulletin 1573-1582.
11. Rodriquez-Lanetty, M., Marquez, L.M. and F. Losada. 2003. Changes in gorgonian morphology along a depth gradient at Isla Alcatrez, San Esteban National Park, Venezuela. Bulletin of Marine Science 72(3):1019-1024.
12. Rossi, S., Rikes, M., Comon, R. and J.M. Gill. 2004. Temporal variability in zooplankton prey capture rate of the passive suspension feeder Leptogorgia sarmentosa (Cnidaria: Octocorallia) a case study. Marine Biology 144(1):89-100.
13. Sung, P.J., Fan, T.Y., Chen, M.C., Fang, L.S., Lim, M.R. and P.C. Chang. 2004. Junceellin a praelolide, two briaranes from the gorgonian corals Junceella fragilis and Junceella juncea (Ellisellidae). Biochemical Systematics and Ecology 32(1):111-114.
14. Todd, R.A., Sidle, R.C. and N.J.I. Lewin-Koh. 2004. An aquarium experiment for identifying the physical factors inducing morphological change in two massive scleractinian corals. Journal of Experimental Marine Biology and Ecology 299(1):97-114.
15. vanOppen, M.J.H. 2004. Mode of zooxanthella transmission does not affect zooxanthella diversity in Acroporid corals. Marine Biology 144(1):1-8.
16. Wellington, G.M. and W.K. Fitt. 2003. Influence of UV radiation on the survival of larvae from broadcast spawning reef corals. Marine Biology 143(6):1185-1192.
17. Yacobovitch, T., Benyahu, Y. and V.M. Weis. 2004. Motility of zooxanthellae isolated from the Red Sea soft coral Heteroxenia fuscescens. Journal of Experimental Marine Biology and Ecology 298(1):3-20.

Coral Diseases

1. Coles, S.L. and B.E. Brown. 2003. Coral bleaching – Capacity of acclimatization and adaptation. 183-224. Advances in Marine Biology 46 Ed: A.J. Southwards, P.A. Taylor, C.M Young and L.A. Fuiman. 352 pg. ISBN 0-12-026146-4.
2. Raymundo, L.J.H., Harvell, C.D. and T.L. Reynolds. 2003. Porites ulcerative white-spot disease: description, prevalence, and host range of a new coral disease affecting Indo-Pacific reefs. Diseases of Aquatic Organisms 56(2):95-104.

Crustaceans

1. Mazel, C.H., Cronin, T.W., Caldwell, R.L. and N.J. Marshall. 2004. Fluorescent enhancement of signaling in a mantis shrimp. Science 303(5654):51.

Ecology

1. Denny, C.M. and R.C. Babcock. 2004. Do partial marine preserves protect reef fish assemblages? Biological Conservation 116(1):111-118.
2. Quinn, N.J. and B.L. Kojis. 2003. The dynamics of coral reef community structure and recruitment patterns around Rota, Saipan and Tinian, western Pacific. Bulletin of Marine Science 72(3):979-996.

Filtration Systems

1. Alonso, J.M., Valdes, M., Calleja, A.J., Ribug, J. and J. Losada. 2003. High frequency testing and modeling of silent discharge ozone generators. Ozone Science and Engineering 24(4):363-376.
2. Brinkman, T., Sartorius, D. and F.H. Frimmel. 2003. Photo-bleaching of humic rich dissolved organic matter. Aquatic Sciences 65(4):415-424.
3. Gerard, M.C., Barthelemy, J.P. and A. Copin. 2003. Influence of ozonation of humic and fulvic acids on diuron adsorption on activated carbon. Ozone Science and Engineering 24(4):399-408.
4. Liang, C.H., Chiang, P.C. and E.E. Chang. 2003. Systematic approach to quantify adsorption and biodegradation capacities on biological activated carbon following ozonation. Ozone Science and Engineering 24(4):351-362.
5. White, E.m., Vaughan, P.P. and R.G. Zepp. 2003. Role of the photo-fenton reaction in the production of hydroxy radicals and photobleaching of colored dissolved organic matter in a coastal river of the southeastern United States. Aquatic Sciences 65(4):402-414.

Fish

1. Baldwin, C.C. and D.G. Smith. 2003. Larvae of gobiidae (Teleostei: perciformes) of Carrie Bow Caye, Belize, Central America. Bulletin of Marine Science 72(3):639:674.
2. Begg, K. and N.W. Pankhurst. 2004. Endocrine and metabolic responses to stress in a laboratory population of the tropical damselfish Acanthochromis polycanthus. Journal of Fish Biology 64(1):133-145.
3. Cheney, K.L. and I.M. Cote. 2003. Do ectoparasites determine cleaner fish abundance? Evidence on two spatial scales. Marine Ecology Progressive Series 283:189-196.
4. Choudhury, S., Pattnaik, P., Sree, A., Bapuji, M. and S.C. Mukherjee. 2003. Antibacterial activity of sponge extracts against fish pathogens. Aquaculture Research 34(12):1075-1078.
5. Elliott, J.P. and D.R. Bellwood. 2003. Alimentary tract morphology and diet in coral reef fish families. Journal of Fish Biology 63(6):1595-1609.
6. Fisher, R. and D.R. Bellwood. 2003. Undisturbed swimming behaviour and nocturnal activity of coral reef fish larvae. Marine Ecology Progressive Series 283:177-188.
7. Green. B.S. and R. Fisher. 2004. Temperature influences swimming speed, growth and larval duration in coral reef fish larvae. Journal of Experimental Marine Biology and Ecology 299(1):115-129.
8. Kolm, N. and J. Olsson. 2003. Differential investment in the Banggai cardinalfish: can females adjust egg size close to egg maturation to match the attractiveness of a new partner? Journal of Fish Biology 63a:144-151.
9. Lecchini, D., Adjeroud, M., Pratchett, M.S., Cadoret,L. and R. Galzin. 2003. Spatial structure of coral reef fish communities in the Ryukyu Islands, southern Japan. Oceanologica Acta 26(5-6):537-548.
10. Ramirez-Mella, J.T. and J.R. Garcia-Sais. 2003. Offshore dispersal of Caribbean reef fish larvae: How far is it? Bulletin of Marine Science 72(3):997-1018.
11. Sales, J. and G.P.J. Janssens. 2003. Nutrient requirements of ornamental fish. Aquatic Living Resources 16(6):533-540.
12. Smith, S.E., Kane, A.S. and A.N. Popper. 2004. Noise-induced stress response and hearing loss in goldfish ( Carassius auratus ). Journal of Experimental Biology 207(3):427-436.
13. Sponaugle, S. and D.R. Pinkard. 2004. Impact of variable pelagic environments on natural larval growth and recruitment of the reef fish Thalassoma bifasciatum. Journal of Fish Biology 64(1):34-54.

Macroalgae/Marine Plants/Freshwater Plants

1. Jaubert, J.M., Chisholm, J.R.M., Minghelli-Roman, A., Marchioretti, M., Morrow, J.H. and H.T. Ripley. 2003. Re-evaluation of the extent of Caulerpa taxifolia development in the northern Mediterranean using airborne spectrographic sensing. Marine Ecology Progressive Series 283:75-82.
2. Krauss, K.W. and J.A. Allen. 2003. Influences of salinity and shade on seedling photosynthesis and growth of two mangrove species, Rhizophora mangle and Bruguiera sexangula, introduced to Hawaii. Aquatic Botany 77(4):311-324.
3. Rommens, W., Maes, J., Dekeza, N., Inghelbrecht, P., Nhiwatiwa, T., Holsters, E., Olleyier, F., Marshall, B. and C. Brendaonck. 2003. The impact of water hyacinth ( Eichhornia crassipes ) in a eutrophic subtropical impoundment (Lake Chivaro, Zimbabwe). I. Water quality. Archives fur Hydrobiologie.
4. Stewart, H.L. and R.C. Carpenter. 2003. The effects of morphology and water flow on photosynthesis of marine macroalgae. Ecology 84(11):2999-3012.

Nutrient Cycling

1. Powell, R.T. and A. Wilson-Finelli. 2003.Photochemical degradation of organic iron complexing ligands in seawater. Aquatic Sciences 65(4):367-374.
2. Sunda, W. and S. Huntsman. 2003. Effect of pH, light and temperature on Fe- EDTA chelation and Fe hydrolysis in seawater. Marine Chemistry 834(1-2):35-48.