Competition Among Sessile Organisms on Coral Reefs

DOI: 10.1007/978-94-007-0114-4_20

ABSTRACT Competition among sessile organisms is a major process on coral reefs, and is becoming more important as anthropogenic disturbances
cause shifts in dominance to non-reef builders such as macroalgae, soft corals, ascidians, and corallimorpharians. Long-term
monitoring and field experiments have demonstrated that competition for limited space can exert major impacts on reef biodiversity
and community composition across habitats and regions. Recent experiments also reveal increasingly important roles of allelopathic
chemicals and the alteration of associated microbes in shaping competitive outcomes among benthic space occupiers. Competition
impacts the recruitment, growth, and mortality of sessile reef organisms and alters their population dynamics. Co-settlement
and aggregation of conspecific coral colonies may lead to intense intraspecific competition, including chimera formation and
potential somatic and germ cell parasitism. The complexity of competitive outcomes and their alteration by a wide variety
of factors, including irradiance, water motion, and nutrient levels, results in mostly circular networks of interaction, often
enhancing species diversity on coral reefs. Competition is a model process for revealing impacts of human activities on coral
reefs, and will become increasingly important as alternate dominants gain space at the expense of reef-building corals.

KeywordsInterference competition-exploitation competition-competition-cnidarian-macroalgae-cyanobacteria-scleractinian-corallimorpharian-actinarian-sea anemone-ascidian-zoanthid-fungiid-hydrocoral-octocoral-soft coral-stony coral-coral-sponge-climate change-chimera-growth-mortality-reproduction-competitive network-coral–algal interaction-phase shift-feedback loop-model-allelopathy-herbivory-recruitment-antibiotic-microorganism-bacteria-abrasion-palytoxin-bleaching-disease-natural products-nematocyst-mucus-diversity-community structure-aggression-population-alternate dominant

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