An ARC-Linkage funded project:
Long-term changes in Mackay Whitsunday water quality and connectivity between coral reefs and mangrove ecosystems.

Awarded to University of Queensland, Australian National University, and Stanford University researchers in early 2005, this 3-year project is investigating the critical links between long-term changes in coastal land use, mangrove health, and inshore Great Barrier Reef (GBR) water quality and reef ecosystems. Project reports will be published on this site, primarily for the benefit of our industry partners and interested members of the public. We invite your feedback through the guest.

The Great Barrier Reef
Coral reefs are among the most spectacular and diverse of the world’s ecosystems. The Great Barrier Reef (GBR) of Australia extends over 2400km from north to south, includes 2900 reefs, and covers an area of over 350,000 km2. At least 600 of the world’s 800 hard coral species live along the GBR, providing habitat for thousands of fish species and a wealth of marine organisms. The GBR supports a tourism industry worth $4.2 billion in 2004 (GBRMPA), which is the largest industry in the region and a major contributor to the domestic economy. In 2005 there are ~820 tourism operators and 1500 vessels and aircraft, supporting approximately 1.8 million tourist visits each year.

Background
Most coral reefs worldwide were substantially degraded pre-1900 relative to historical conditions, and even the Great Barrier Reef (GBR), considered the most pristine in existence, is “a quarter to a third of its way to ecological extinction” (Pandolfi et al. 2003, Science). Recent evidence points to declining water quality, combined with overexploitation and climate change, as the primary causes of the global decline in coral reefs (Hoegh-Guldberg 1999, Hughes et al. 2003a, Pandolfi et al. 2003).

The rapid expansion of agriculture (sugar cane and banana plantations), urban and port development, and wetland reclamation associated with tourism and recreation (Duke and Wolanski 2001, Johnson et al. 2001) along the Queensland coast is the most significant influence on inshore water quality in the Great Barrier Reef (GBR) over the past 50 years. In 2001, more than 80% of the GBR catchment (424,000 ha) supported some form of agriculture (GBRMPA 2001), and the majority of studies have indicated a five to ten fold increase in nutrient and sediment delivery into the GBR lagoon since European settlement (Moss et al. 1992, Brodie et al. 2001, GBRMPA 2001, Neil et al. 2002, Prosser et al. 2002, Furnas 2003, McCulloch et al. 2003). This is considered to have had significant implications for biological communities within the Great Barrier Reef Park. Yet debate over the sources and extent of long-term anthropogenic nutrient and sediment enrichment persists.

Objectives
The present study will use remote sensing and novel geochemical tracers of sediments (Ba/Ca) and nutrients (skeletal d15N) from coral reef skeletons to describe the historical changes in water quality and coastal ecosystems of the Great Barrier Reef (GBR) since European colonization (Fig. 1a,b). In particular, we wish to understand how widespread land use change, agriculture, and reduced mangrove cover have impacted coastal GBR water quality, coral reefs, and frequency / severity of flood events. Our methods hav been used successfully to understand changes in sediment flow in the Burdekin region of the Great Barrier Reef (Alibert et al. 2003, McCulloch et al. 2003), to trace altered nutrient compositions (fertilizers and sewage) since 1970 in Bali, Indonesia (Marion et al. 2003), and to identify past nutrient experiments (ENCORE) on the GBR (Hoegh-Guldberg et al. 2004). However, this project marks the first instance in which the latest coral geochemical techniques will be combined into a single, unified study, providing new opportunities to explore marine, climate, and hydrological changes in the central GBR.

Coral geochemical reconstructions of long-term changes in pollutant sources (based on organic nitrogen isotopic ratios, top) and sediment loads (Ba/Ca ratios, bottom) in Mackay Whitsunday coastal waters

Approach
Our primary focus will be the Pioneer River, Mackay region, the “heart” of Queensland’s sugar cane industry and a catchment area that the Great Barrier Reef Marine Parks Authority has prioritized as a “high risk” region of the Reef (GBRMPA 2001). Long (up to 2 m) Porites coral cores will be collected in a 3 km to 150 km transect from offshore of the Pioneer River to the outermost Pompey Reef. A range of analyses will be performed on the coral cores, providing records of pre-instrumental river discharge (from high-resolution measurements of coral luminescence), sedimentary release (via laser ablation inductively coupled mass spectrometry), and nutrient and pollutant sources (nitrogen isotopic analysis of skeletal organic matter). Aerial and satellite imagery will be used to investigate the expansion/contraction of coastal agriculture and mangrove ecosystems related to variation in coastal water quality. The project will extend the coral isotopic proxies using manipulative experiments on Heron and One Tree Islands, while Pioneer river nutrient and isotopic compositions will be determined by water sampling during peak-flow and non-peak flow, over a gradient of salinity and hydrodynamic features.

Remote sensing analysis of aerial photographs and Landsat satellite imagery reveal a species-specific 26% net loss of mangrove cover in the Pioneer catchment since 1948.

Outputs
Results from this project are being communicated through scientific publication, technical reports to our funding partners, conference and workshop talks, and through mainstream media channels. This webpage will serve as a location for project news and updates, which we hope our partners and collaborators will find useful.

By understanding how water quality and marine ecological links have changed historically, sustainable management regimes can be developed to preserve Australia’s relatively pristine Great Barrier Reef. Empirical records of long-term source-sink relationships between nutrient and sediment discharge, floods and coral reefs provide much-needed quantitative data that will directly contribute to the establishment of water quality targets within the Federal and Mackay regional Water Quality Initiative and Plans. Outcomes from this study will not only benefit the Mackay-Whitsunday regional catchment management groups. Management groups and industries may refer to this case study when optimising management practices and water quality targets within historical limits that ensure sustainable agricultural and development. Findings will also aid agricultural unions and regional management groups by identifying fertilizer loss and undesirable downstream effects for industry.

Funding
This research was funded in early 2005 by an Australian Research Council Linkage grant. Industry partners include the Great Barrier Reef Marine Park Authority, the Mackay Whitsunday Natural Resource Management Group (MWNRM), and the Mackay City Council. In addition, early project work was made possible by funding from the PADI Foundation (to G. Marion and S. Jupiter), the Fulbright Association (S. Jupiter), the International Society for Reef Studies / The Ocean Conservancy (to G. Marion), and the Great Barrier Reef Marine Park Authority (G. Marion).