Final report on thresholds and indicators of declining water quality as tools for tropical seagrass management
Other Publication ResearchOnline@JCUAbstract
[Extract] Background. The broad aims of this study were to test the vulnerability of seagrasses to declining water quality, in particular, changes associated with flooding. This project was established in response to extensive seagrass loss that occurred from 2009 to 2011 in the Great Barrier Reef when there was above average run-off for multiple wet seasons, which culminated in the passage of cyclone Yasi through the northern GBR in 2011. Dugong, which are seagrass specialists, also suffered record levels of mortality in 2011 and had low calving rates in the southern GBR following the unprecendented levels of seagrass loss. In 2014, there were signs that seagrass meadows were recovering. This project has been designed to help interpret the effects of flood water on seagrass as well as improve our capacity to detect and respond to other water quality related impacts (e.g. dredging).Flood plumes are low in salinity (hypo-saline), have high nutrient concentrations (triggering blooms of phytoplankton) and both dissolved (e.g. CDOM) and particulate matter (e.g. suspended sediments) that create low light conditions. Floodwaters may also contain toxic levels of contaminants, such as herbicides. This was a 2-year project that included desktop analyses, analysis of in situ light logger data, analysis of remote sensing-derived water quality, a review of the literature and a number of experiments to test seagrass responses to salinity, light and nutrients and to identify thresholds associated with loss. The objectives of this project were to determine:• The level of exposure of seagrass meadows to broad scale and long-term changes in water quality associated with flood plumes in coastal regions of the GBR• The influence of light, nutrients and salinity on seagrass condition• Refined thresholds of concern for light, nutrients and salinity• Indicators of seagrass condition to report on status• Future trajectories for GBR ecosystems.
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978-1-925088-50-2
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60
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James Cook University
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Townsville, Australia
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