mechanisms, as well as fine scale observations of the larvae of species from 

 different reef habitats, deserve extensive research before we will understand 

 this critically important aspect of the biology of coral reef organisms. 



Ronald Karlson summarizes the conclusions of his discussion section on a 

 related topic, life history patterns. An emerging body of research demonstrates 

 that the observed growth rates, form, and longevity of corals along depth 

 gradients result from complex interactions between physical (e.g., light and 

 wave disturbance) and biotic variables. Recent research shows that sublethal 

 phenomena such as injuries due to physical and biotic agents have significant 

 implications for growth and reproduction in many sessile reef organisms. These 

 processes can vary significantly in different habitats. This discussion group 

 also addressed the important topic of ecological and evolutionary patterns in 

 solitary vs. colonial organisms on coral reefs. The importance of fission, 

 fusion, and fragmentation (and thus of colony size) in both solitary and colonial 

 species received particular attention as a productive avenue for future research. 



Mark Hixon lead the discussion section on community structure and function. 

 Coral reef ecologists have been in the forefront of the debate on whether 

 communities are organized by stable predictable processes or whether they 

 merely represent independent populations in shifting states of disequi 1 ibria. 

 One of the reasons that disequilibrium and stochastic processes have been so 

 apparent in coral reef communities may be because dispersing, feeding larvae 

 engender unpredictable recruitment. However, recent research also has demon- 

 strated the importance of irregular catastrophic perturbations, such as storms 

 (e.g., Woodley, et al . , 1981), population outbreaks (e.g., Birkeland, 1982), or 

 diseases (e.g., Lessios, et al . , 1984) in the organization of coral reef communi- 

 ties. One of these events, the mass mortality of Caribbean sea urchin populations, 

 was ongoing at the time of the workshop and was a major topic of discussion. 

 Although the causes and mechanisms of this outbreak still are not well under- 

 stood, Hixon identifies the heuristic value of this "natural experiment" which 

 has removed a major herbivore over large local and geographical areas of reefs. 

 This discussion lead to an evaluation of a more deterministic process, herbivory 

 by urchins vs. fishes, on reefs; this discussion centered on how human activities 

 such as fishing in certain well studied localities can affect our interpretations 

 of the past and present organization of reef communities. Although terrestrial 

 and fresh water ecologists have been concerned about the effects of human inter- 

 vention on natural communities for some time, the pervasiveness of this problem 

 in coral reef communities has attracted attention only recently. Hixon argues 

 that one of the most critical needs for future research is for experimental 

 manipulations and long term comparative studies. 



The discussion section on community metabolism was led by Stephen Smith. 

 Smith shows how this field has developed from a focus on oxygen and carbon flux 

 to studies of the physical, chemical, and biological variables that control 

 metabolism of the reef ecosystem. The discussion addressed how the quantity and 

 quality of available nutrients affect productivity, how nutrient flux between sub- 

 communities can affect nutrient balance of the overall reef ecosystem, and how new 

 technological approaches can improve our ability to measure community metabolism. 

 Smith stresses that a holistic approach, including comparisons with other ecosys- 

 tems, will represent important avenues for future research in this area. 



