Abstract
A strong driver of water quality change in the Great Barrier Reef (GBR) is the pulsed or intermittent nature of terrestrial inputs into the GBR lagoon, including delivery of increased loads of sediments, nutrients, and toxicants via flood river plumes (hereafter river plumes) during the wet season. Cumulative pressures from extreme weather with a high frequency of large scale flooding in recent years has been linked to the large scale reported decline in the health of inshore seagrass systems and coral reefs in the central areas of the GBR, with concerns for the recovery potential of these impacted ecosystems. Management authorities currently rely on remotely-sensed (RS) and in situ data for water quality monitoring to guide their assessment of water quality conditions in the GBR. The use of remotely-sensed satellite products provides a quantitative and accessible tool for scientists and managers. These products, coupled with in situ data, and more recently modelled data, are valuable for quantifying the influence of river plumes on seagrass and coral reef habitat in the GBR. This article reviews recent remote sensing techniques developed to monitor river plumes and water quality in the GBR. We also discuss emerging research that integrates hydrodynamic models with remote sensing and in situ data, enabling us to explore impacts of different catchment management strategies on GBR water quality.
Highlights
Coastal zones are experiencing increasing pressure from anthropogenic activities, compounded by a rapidly rising human population, with more than 60% of the world’s population located within the coastal zone [1,2]
The current water quality program includes: (1) in situ ambient and wet season monitoring of sediments, nutrients, and pesticides [31,46,47], and (2) through a range of remote sensing techniques supported by the development of regionally specific algorithms, producing regionally-tuned MODIS ocean colour products for the Great Barrier Reef (GBR) [36,37]
Prior to RS imagery being accessible via free satellite imagery, the dispersion of river plumes in the GBR lagoon was mapped using a combination of aerial photography, in situ water quality and salinity sampling from vessels [9,21,23]
Summary
Coastal zones are experiencing increasing pressure from anthropogenic activities, compounded by a rapidly rising human population, with more than 60% of the world’s population located within the coastal zone [1,2]. Reef Integrated Monitoring Program (P2R Program) [18] has been designed to support this evaluation and includes indicators of the adoption of improved land management practices, catchment condition, end of catchment pollutant load estimates, and marine water quality and ecosystem health. OACs concentrations with RS techniques is notoriously challenging in optically complex (Case 2) coastal waters [8,45], which include the area of inshore GBR lagoon, typically within 20 km of the coast [35,37] These limitations of the RS data must be understood and reported in order to efficiently use this data as an appropriate monitoring tool for the measurement and reporting of water quality in the GBR. RS products presented here have been developed from post processing of RS data and applied in the monitoring of acute (river plumes) and chronic wet season water quality conditions in the GBR. We acknowledge the current challenges in utilising these data sources, and describe future developments of integrating RS data and products with modelling outputs that will continue to extend our ability to make spatial and temporal assessments of water quality across the GBR
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