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Lethal and sub-lethal impacts on dredge related stressors on corals

IOMRC AUDITORIUM  Phd Completion Presentation: 
Lethal and sub-lethal impacts on dredge related stressors on corals

Thursday 02 March, 4pm. 

Seminar Abstract:

Corals are the framework builders of coral reefs and face a suite of both global and local pressures. One of the most prominent local stressors is sedimentation resulting from river-runoff, natural resuspension events, and dredging. Dredging involves the excavation of sediment from the sea floor to allow coastal construction, land reclamation, industrial development, and the creation of ports and shipping channels. Over the past 50 years more economically efficient transportation of goods has resulted in increasing ship size, with a doubling of draft requirements. This increasing ship size and rapidly expanding coastal development has resulted in increased dredging. In tropical Australia this is particularly evident, with 72M m3 of sediment being dredged over the past 20 years to facilitate the exportation of coal, iron ore, and liquefied natural gas. To effectively manage these projects and minimise the impacts on nearby coral reef ecosystems an increased knowledge of the impacts of sediment related stressors on corals is required, along with the development of thresholds to guide the dredging activity and subsequent water quality conditions generated. This project has investigated the impacts of a large scale (~3M m3 of seafloor substrate removed) dredging project in the north west of Australia on coral health, and performed corresponding laboratory experiments investigating the specific causal pathways of sediment related pressures, including suspended sediment concentrations (SSCs) and light reduction. From this, we have developed threshold guidelines. In addition to this, cumulative impacts of both locally (sediment) and globally-relevant (temperature) pressures were investigated. Collectively, these data demonstrate that dredge-related water quality conditions impact considerably on coral health. This appears to be particularly apparent for light attenuation, which has been investigated thoroughly here, and deposited sediment, which requires further investigation. It also demonstrated that cumulative impacts resulting from dredge-related pressures and increased temperatures reduce coral health further and therefore these need to be appropriately managed to minimise dredge related stress when coral communities are simultaneously exposed to temperature stress and subsequent bleaching events. 

Pia Bessell-Browne 

Bessell-Browne P, Negria A.P., Fisher R, Clode P.L., Duckworth A, Jones R, (2017) Impacts of turbidity on corals: The relative importance of light limitation and suspended sediments Marine Pollution Bulletin 2017

IOMRC auditorium, UWA

Thu 02 Mar 2017 To Thu 02 Mar 2017

4:00pm To 5:00pm