No effect of dredging on the prevalence of coral disease detected during a large dredging program.

Abstract The frequency of disease within coral communities was evaluated using an 18-month series of coral photographs taken before, during, and after a major dredging program at Barrow Island, off Australia's northwest coast. Up to 60 corals were assessed repeatedly at each of four dredging 'impact' sites (<1 km from dredging), and four 'reference' sites (>20 km from dredging). Contrary to an earlier report, the frequency of occurrence of coral disease (usually <5% of corals) was not significantly altered by dredging. The pattern of occurrence of coral disease does not constitute a suitable early warning bioindicator of dredging impacts on coral. This study suggests that disease is difficult to measure and evaluate, and is not a key indicator in the potential impacts of dredging on coral health. We propose that environmental monitoring during dredging should continue to focus on known impact indicators. Highlights • Investigation showed no increase in coral disease during or after a large dredging program. • Disease may occur naturally in many coral communities without much impact. • Coral disease is not a suitable indicator of dredging impacts. • Visual diagnosis of some coral diseases may be unreliable. [ABSTRACT FROM AUTHOR]