GROWTH AND LIFE HISTORY PATTERNS OF CORAL REEF ORGANISMS: 

 A DISCUSSION GROUP SUMMARY AND OVERVIEW 



Ronald H. Karlson 

 Ecology and Organismic Biology Program 

 School of Life and Health Sciences 

 University of Delaware 

 Newark, Delaware 19716 



I would like to take this opportunity to thank all who attended our late 

 evening discussion group. Although it would have been impossible for us to 

 deal with all major taxa of coral reef organisms, we discussed a reasonably 

 diverse array of colonial organisms and a group of solitary echinoderms. 

 Taxonomic areas of research and a partial list of participants include actinians 

 (Sebens), bryozoans (Jackson), corals (Brakel, Highsmith, Hughes, Hunter, 

 Jackson), echinoderms (Highsmith, Keller, Levitan, Mladenov), gorgonians 

 (Harvell, Lasker, Wahle), sponges (Harvell, Pomponi , Suchanek), and zoanthids 

 (Karlson, Sebens, Suchanek). 



Six short presentations by Brakel, Hughes, Suchanek, Wahle, Karlson, and 

 Mladenov were given in our discussion session. Each was followed by questions 

 and/or discussion. Each presentation dealt with variability in one or more of 

 the following: growth form, growth rate, overgrowth frequency, fecundity, 

 survivorship, colonial integrity, or reproductive mode. We also discussed size- 

 specific variation in life histories, fission, fusion, and brooding in coral 

 reef invertebrates. 



Brakel's presentation dealt with depth-related variation in the growth 

 form of Porites astreoides (Brakel, 1983). He noted that much of the literature 

 dealing with coral growth form suggests that there may be a simple monotonic 

 relationship between colony shape and depth. Brakel's analysis indicates that 

 flattened colonies are typical of high-energy, shallow water habitats and of 

 low-light, deep water habitats. Between these two extremes, wave energy and 

 light set upper limits on morphological variation and are not good predictors 

 of mean morphological parameters. 



Three additional citations to those given by Brakel (1983) on the general 

 relationship between colony morphology and depth are Fricke and Schuhmacher 

 (1983), Chappell (1980), and Steam (1982). The first is an interesting paper 

 on photoadaptations in deep hermatypic corals found down to 145 m. They noted 

 the prevalence of flat hermatypes in deep water and a great diversity of growth 

 forms in shallow water. This pattern was not observed for ahermatypic corals. 

 Chappell (1980) discussed the effects of light and wave stress on coral growth 

 form and rate and extended these effects to include the growth of coral reefs. 

 Steam (1982) critically reviewed the analysis of growth form in corals and 

 stromatoporoids. He, like Brakel, concluded that the relationship between 

 growth form and environmental variables is quite complex due to the influences 

 of genetic and developmental processes. 



The presentation by Hughes (1983) dealt with coral growth rates as well 

 as life history variation over a depth range. The major point of this presentation 



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