The Great Barrier Reef Ocean Observing System Mooring array: Monitoring the Western Boundary Currents of the Coral Sea and Impacts on the Great Barrier Reef
Since 1987 Great Barrier Reef weather and water temperature observations have been transmitted in near real
time using HF radio from pontoons or towers on coral reefs by AIMS. In contrast oceanographic
measurements have however been restricted to loggers serviced at quarterly to half yearly downloads.
The Great Barrier Reef Ocean Observing System (GBROOS) is a regional node of the Integrated Marine
Observing System (IMOS). IMOS is an Australian Government initiative established under the National
Collaborative Research Infrastructure Strategy and has been supported by Queensland Government since
2006. GBROOS comprises real time observations from weather stations, oceanographic moorings, underway
ship observations, ocean surface radar, satellite image reception and reef based sensor networks.
This paper focuses on an array of in-line moorings that have been deployed along the outer Great Barrier Reef
in order to monitor the Western Boundary currents of the Coral Sea. The Westward flowing Southern Equatorial
Current bifurcates into the poleward flowing East Australian Current and the equatorward North Queensland
The 4 mooring pairs consist of a continental slope mooring, nominally in 200m of water and one on the outer
continental shelf within the GBR matrix in depths of 30 to 70m. The array is designed to detect any changes in
circulation, temperature response, mixed layer depth and ocean-shelf interactions. A review of likely impacts of
climate change on the physical oceanography of the GBR is providing a basis upon which to explore what
processes may be affected by climate change. Sample data and results from the initial year of observations
will be presented.
Isotopic and Physiological Effects of Disease in a Sea Fan from Bermuda
Aspergillosis, a disease caused by the fungus, Aspergillus sydowii, has impacted gorgonian populations throughout much of the Caribbean, including Bermuda. Stable carbon (δ13C) and nitrogen (δ15N) isotopes have been shown to be a useful tool for tracking physiological changes in coral species. To assess the relationship between δ13C, δ15N, and physiological effects of disease in corals, healthy and diseased colonies of the purple sea fan (Gorgonia ventalina) were analyzed. Visibly healthy and diseased samples were collected from a near-shore reef location in July 2007. Healthy samples were also collected from an off-shore reef location, where there was no visible incidence of disease on the reef. The proportion of purpled sclerites was measured for each sample and verified the severity of disease for each colony. Diseased sections of G. ventalina had lower lipid concentrations than healthy sections of the same colony, suggesting that lipid stores are selectively utilized within each colony. Interestingly, healthy sections from near-shore colonies where disease was present had more lipid stores than healthy sections from off-shore colonies where disease was absent. Total biomass was greatest in healthy off-shore colonies. Both δ13C and δ15N did not differ between healthy and diseased colonies, but were more enriched in near-shore compared to off-shore locations. These preliminary results suggest that consumption of lipid stores may be a species-wide physiological strategy amongst corals for coping with stressful events and that soft corals may track levels of local land-based pollution.
Satellite SST Trends and Climatologies - how many years is enough?
Stress on coral reef ecosystems is generally due to abnormal events, rather than absolute levels, of environmental conditions (e.g., temperature, salinity, and light). For example, ocean temperatures of 30°C would be "comfortable" for corals in the Persian Gulf but stressful for the corals off the coast of Brazil because they are accustomed to different conditions. Identifying anomalous conditions requires good knowledge of the baseline ("usual", "normal") conditions. Here we discuss whether a remotely-sensed, 4km sea surface temperature (SST) record of length 23 years is sufficient to calculate a long-term average (climatology) that can sensibly be used as a baseline for monitoring the health of corals. We also discuss issues related to ocean warming in determining this baseline and the relevance of adaptation by corals.
Predicting the onset and severity of coral bleaching and mortality using satellite-observed light and temperature
The NOAA Coral Reef Watch (CRW) suite of satellite products is designed to help coral reef managers monitor
thermal stress to better understand and predict mass coral bleaching. The current products are based purely
on ocean temperature, and yet both temperature and light contribute to mass coral bleaching. A new satellite-
derived solar radiation product has been developed and, when combined with the thermal stress indices, is
expected to improve predictions of the severity of mass coral bleaching events and resultant mortality. Here, we
describe the development of a new coral physiology-based method to predict coral bleaching based on the
total Light Stress Damage experienced by the coral holobiont.