Our scientists lead seagrass and inshore water quality monitoring across large areas of the inshore Great Barrier Reef Marine Park, contributing critical data to the recently released 2022-23 Marine Monitoring Program Annual Report. (see summary here).
For nearly 20 years we've contributed to the Marine Monitoring Program, assessing water quality and seagrass meadows to understand the impacts of land-based runoff on the Reef, cyclones, floods, and rising ocean temperatures.
The report: what do the results reveal?
The 2022-23 report reveals seagrass conditions have an overall ‘moderate’ condition score. Yet, regions vary considerably, ranging from ‘very poor’ to ‘good’.
While water quality has seen years of deteriorating trends, the latest results show encouraging overall improvements across all monitored regions.
JCU TropWATER’s Jane Waterhouse said despite this, some key indicators do not meet water quality guideline values. Substantial improvements will need to be made for guideline values to be met.
“Further work is needed to determine whether the positive trends in inshore water quality conditions can be linked to improvements in land management. We need to understand if the changes are widespread and sustained over time, especially in the context of other major drivers such as climate,” she said.
The Great Barrier Reef Marine Park Authority’s Marine Monitoring Program is a partnership between JCU TropWATER, the Australian Institute of Marine Science (AIMS), and the Cape York Water Partnership. The Program also includes inshore coral reef monitoring, undertaken by AIMS.
Water quality: how do we monitor conditions?
Good water quality is essential for the health of marine and freshwater ecosystems. When water quality improves, the resilience of these ecosystems strengthens.
Our scientists partner with the Cape York Water Partnership and the Australian Institute of Marine Science to collect and analyse water quality data from several sources. This data provides important insights into the concentrations and transport of land-sourced pollutants in the inshore Great Barrier Reef.
Our team conducts year-round water quality sampling across inshore areas in Cape York, Wet Tropics, Burdekin, Mackay Whitsunday, and Fitzroy regions. Sampling frequency increases during the wet season and flood events.
Using this ground-based data, we leverage our in-house expertise in remote sensing technologies. By integrating satellite imagery, we can map and monitor water quality conditions across vast areas of the Reef.
Seagrass: how do we monitor conditions?
Seagrasses are powerful carbon sinks. They are vital food sources for dugongs and green turtles and serve as essential nurseries for prawns and fish.
Our scientists monitor inshore seagrass meadows across the Reef in various habitats. We assess their resilience and abundance through percentage cover, species composition, and reproductive status (presence of flowers, fruits, and seeds). Monitoring occurs in the late-dry and late-wet seasons.
To understand seagrass conditions, we also record factors like seawater temperature, light availability, sediment characteristics, and the presence of macroalgae and epiphytes. This data gives us a comprehensive assessment of seagrass conditions in each region.
Summary 2022-23 monitoring results
Water quality and seagrass monitoring were undertaken at each region, which includes subregion assessments.
Cape York
Water quality in the Cape York region scored 'good'. River discharge ranged from 1.5 to 1.9 times the long-term median, except for the Normanby River, which was 3.1 times higher. The Normanby flood plume extended across Princess Charlotte Bay, reaching up to 100 km east, beyond the outer reefs. Most indicators met guideline values at most sites, but inorganic nitrogen and water clarity did not.
Seagrass scored ‘moderate’. Seagrass abundance increased, but resilience declined from 'moderate' to 'poor'. Reproductive structures were rarely observed for the third consecutive year, impacting seed bank replenishment and recovery capacity.
Wet Tropics
Water quality in the Wet Tropics region was rated 'moderate'. Over the past two to five years, water quality has shown an improving trend in most parts of the Wet Tropics. Some nutrient levels and water clarity did not meet guidelines in all sub-regions, while other indicators did. For example, Particulate nitrogen met guidelines in two sub-regions but showed deterioration in the Tully sub-region.
Seagrass condition is assessed in two separate sub-regions, with an overall 'moderate'. Seagrass condition improved in the northern meadows driven by more resilient meadows, while the south saw declines in both abundance and resilience for the second consecutive year. Extreme weather events in 2011 continue to hamper recovery in the southern region.
Burdekin
Water quality in the Burdekin region scored 'moderate'. River discharge was 2.2 times the long-term median, after two years of near-median levels. Some nutrient levels and water clarity did not meet guidelines. After declines from 2010-2018, water quality has stabilised and shown improvements, driven by lower nutrient levels and better water clarity.
Seagrass meadows have deteriorated overall but remained 'moderate'. Seagrass abundance marginally decreased compared to the previous period and remains lower than historical records. Seagrass resilience also slightly decreased despite abundant seed banks.
Mackay-Whitsunday
Water quality in the Mackay-Whitsunday region was 'moderate'. River discharge was 1.7 times the long-term median after three years of below-average levels. Most water quality indicators, such as nutrient levels and water clarity, did not meet guidelines. A positive trend has seen a reverse in the decline from 2007-2018, sparking optimism for the region's water quality.
Seagrass in this region was 'moderate'. Seagrass condition has fluctuated between 'poor' and 'moderate' since 2011-12 due to various environmental pressures. In 2022-23, the seagrass abundance score increased, driven by estuarine intertidal and coastal and reef subtidal habitats. Resilience also improved to its highest level in six years, indicating potential recovery from past disturbances.
Fitzroy
Water quality in the Fitzroy region was ‘good’ and is conducted by AIMS. River discharge was around the long-term median. Some nutrient levels and water clarity did not meet guidelines. It is difficult to assess trends in the region due to a gap in the sampling from 2015 to 2020.
Seagrass condition slightly deteriorated and remained 'poor', continuing a three-year decline. While the seagrass abundance score marginally improved, this was driven by only one estuarine intertidal site, keeping the overall score 'poor'. Resilience decreased to the second lowest level recorded., also remaining 'poor'.
Burnett Mary
Seagrass meadows declined further in 2022-23, reaching a 'very poor' grade for the first time in 16 years. The seagrass abundance score remained very poor for the second consecutive year, continuing a downward trend since 2015-16. Despite this, persistent seed banks give meadows some recovery potential, though reduced replenishment ability makes them vulnerable to future disturbances.
