James Cook University

About: James Cook University is a education organization based out in Townsville, Queensland, Australia. It is known for research contribution in the topics: Population & Coral reef. The organization has 9101 authors who have published 27750 publications receiving 1032608 citations. The organization is also known as: JCU.

Factors controlling suspended sediment on inner-shelf coral reefs, Townsville, Australia

Abstract: This study was undertaken to describe the characteristics of suspended sediment concentrations (SSCs) of marine waters near inner-shelf fringing coral reefs and relate these to the prevailing oceanographic and meteorological conditions. Using logging optical backscatter nephelometers, SSCs were measured at fringing reefs at Magnetic Island and on the adjacent inner-shelf, Cleveland Bay, N.E. Australia. Continuous measure-ments were made over a period of 4 months, representing possibly the most comprehensive set of SSC data collected near coral reefs. Wind, current and wave data were also collected. Temporal and spatial variation in near-bed SSCs is high. Periods of strong southeasterly regional winds generate swells, which, within 1 km of the reefs, produce near-bed SSCs of well over 200 mg/l. At the fringing coral reefs at Arthur and Geoffrey Bays, SSCs were less than 5 mg/l for most of the time and rarely exceeded 40 mg/l, but there were a number of periods of over 24 h when near-bed SSCs continuously exceeded 20 mg/l. The height of locally produced, short-period wind-waves is the dominant control on the magnitude of near-bed SSCs at the reef sites, and thus the wind regime heavily influences conditions for coral communities. The magnitude of the tide is of lesser importance. However, it is likely that flushing of these bays by tidal currents is important in preventing a long-term build-up of SSC in the water around the coral reefs.

Habitat utilization by coral reef fish: implications for specialists vs. generalists in a changing environment

Abstract: 1. The impact of environmental disturbance and habitat loss on associated species is expected to be dependent on a species' level of specialization. We examined habitat use and specialization of coral reef fish from the diverse and ecologically important family Pomacentridae, and determined which species are susceptible to declines in coral cover due to disturbance induced by crown-of-thorns seastar (COTS, Acanthaster planci L.). 2. A high proportion of pomacentrid species live in association with live coral as adults (40%) or juveniles (53%). Adults of many species had strong affiliations with branching corals, while juveniles favoured plating growth forms, reflecting the sizes of refuge provided by coral types. 3. Juveniles of species that associated with coral had narrower niche breadths than adult conspecifics, due to associations with specific coral types. The especially high coral association and narrower niche breadth of juveniles suggest that the presence of live coral is crucial for many species during early life history, and that disturbance-induced coral loss may have serious flow-on effects on adult abundance. 4. Microhabitat availability was a poor predictor of fish species abundance. Significant correlations between coverage of coral types and abundance of five adults and two juvenile species were detected; however, these relationships explained <35% and <10% of the variation in abundance of adult and juvenile species, respectively. 5. Niche breadth explained 74% of the variation in species' mean response to coral decline and it is clear that disturbance has a greater impact on resource specialists, suggesting that increasing frequency and intensity of coral loss will cause reef fish communities to become dominated by habitat generalists at the expense of coral-dwelling specialists.

Recovery without resilience: persistent disturbance and long-term shifts in the structure of fish and coral communities at Tiahura Reef, Moorea

Abstract: Disturbances have a critical effect on the structure of natural communities. In this study long-term changes were examined in the reef community at Tiahura Reef, on the northern coast of Moorea, which had been subject to many and varied disturbances over the last 25 years. Tiahura Reef was subject to an outbreak of crown-of-thorns starfish (Acanthaster planci) in 1980–1981, causing significant declines in the abundance of scleractinian corals and butterflyfishes. By 2003, the abundance of corals and butterflyfishes had returned to former levels, but despite this apparent recovery, the species composition of coral communities and butterflyfish assemblages was very different from those recorded in 1979. Ongoing disturbances (including further outbreaks of crown-of-thorns starfish, cyclones, and coral bleaching events) appear to have prevented recovery of many important coral species (notably, Acropora spp.), which has had subsequent effects on the community structure of coral-feeding butterflyfishes. This study shows that recurrent disturbances may have persistent effects on the structure and dynamics of natural communities.