A Long‐term Study of Competition and Diversity of Corals

Abstract

Variations in interspecific competition, abundance, and alpha and beta diversities of corals were studied from 1962 to 2000 at different localities on the reef at Heron Island, Great Barrier Reef, Australia. Reductions in abundance and diversity were caused by direct damage by storms and elimination in competition. Recovery after such reductions was influenced by differences in the size of the species pools of recruits, and in contrasting competitive processes in different environments. In some places, the species pool of coral larval recruits is very low, so species richness (S) and diversity (D) never rise very high. At other sites, this species pool of recruits is larger, and S and D soon rise to high levels. After five different hurricanes destroyed corals at some sites during the 38year period, recovery times of S and D ranged from 3 to 25 years. One reason for the variety of recovery times is that the physical environment was sometimes so drastically changed during the hurricane that a long period was required to return it to a habitat suitable for corals. Once S and D have peaked during recolonization, they may either remain at a high level, or decline. In shallow water, with no deleterious changes in environmental conditions, S and D may not decline over time, because superior competitors cannot overtop inferior competitors without exposing themselves to deleterious aerial exposure at low tide. At other times and places, S and D did decline over time. One cause of this was a gradual deterioration of the physical environment, as corals grew upward into the intertidal region and died of exposure. S and D also fell because the wave action in hurricanes either killed colonies in whole or part, or changed the drainage patterns over the reef crest, leaving corals high and dry at low tide. At deeper sites, declines in S and D were sometimes caused by heavy wave action, or by interspecific competition, as some corals overgrew or overtopped their neighbors and eliminated them.

Exploring coral reef responses to millennial-scale climatic forcings: insights from the 1-D numerical tool pyReef-Core v1.0

“…Thirdly, the estimation of the interaction matrix coefficients and Malthusian parameters remains difficult (Clavera-Gispert et al, 2017), specifically when considering coral assemblage dynamics at the temporal scale (decadal to centennial) relevant to pyReefCore. Yet interpretations of these parameters from ecological modelling studies provide a useful guide with regard to reef biozonation and assemblage competition (Lang and Chornesky, 1990;Grigg, 2002;Connell et al, 2004). Finally, modelled vertical accretion or growth patterns in pyReefCore are non-linear reflecting the natural complexity of coral reef systems and the biological and physical interactions occurring at reef scales.…”

“…Over longer timescales, they also shape the rate of calcium-carbonate production, framework building by corals and the accumulation of sedimentary deposits (Done, 2011). Despite the significant, short-term impacts cyclonic storms and terrigenous sediment input can have on reef systems (Cubasch et al, 2013), episodic disturbances are smoothed out on geologic scales (10 000s years) where reef systems are characterised by remarkable persistence and resilience (Precht and Aronson, 2016). The persistent factors (e.g.…”

“…As assemblages occupy ecological niches, each will spatially dominate at a location under specific environmental conditions, outcompeting other assemblages for food, space and light (Connell et al, 2004). Hence, competition is an important determinant of reef biozonation which persists over centennial timescales given that coral growth is slow and colony lifespans can be centuries long.…”

“…Empirical studies of coral competition and growth are often focused at the species rather than assemblage level and explain competitive relationships qualitatively rather than quantitatively (e.g. Connell et al, 2004). Moreover, GLVEs have not been used to model coral population dynamics at the temporal resolution (centennial to millennial) we are interested in.…”

Spongivory by Fishes on Southwestern Atlantic Coral Reefs: No Evidence of Top-Down Control on Sponge Assemblages

“…Furthermore, predation may reduce competitive exclusion by decreasing abundances of superior competitors (Paine, 1966;Hay, 1991). Competition for space is often an important regulator process in marine hard bottoms, as coral and rocky reefs, and influences patterns of abundance and diversity of biological assemblages (Connell et al, 2004;Chadwick and Morrow, 2011).…”