The northern boundary of the South inshore reporting zone extends due eastward from the mainland just south of the Moresby River at Double Point to the boundary of the offshore waters and includes enclosed coastal, open coastal and mid-shelf waters. The southern boundary of the South zone extends east from the North West bank of the Seaforth Channel mouth, just south of Hinchinbrook Island, to the offshore boundary.
The major rivers discharging into the South zone are the Tully River and the Murray River. The Hull River discharges to the north of the Tully River. Several smaller waterways drain sub catchments that are dominated by agricultural land use, for example Liverpool Creek and Maria Creek, which discharge into the South zone. Numerous smaller creeks discharge to the north of and within Hinchinbrook Channel.
Water quality in the South inshore zone is affected by plumes of sediments, nutrients and pesticides from rivers and creeks discharging directly into the zone but also from the plumes of southern rivers, particularly the Herbert and also the Burdekin located in the Dry Tropics NRM region.
The area includes the Barnard Island group some 7 km east of Cowley Beach, North and South Dunk Island some 7.5 km south east of Mission Beach, and the Bedarra Island group located several kilometres south of the Dunk Island group. The area also includes Hinchinbrook Island. These islands provide fringing shallow water environments that support coral reef ecosystems and intertidal and subtidal reef seagrass meadows. Extensive seagrass meadows fringe the northern and western coastal areas of Hinchinbrook Island. Intertidal coastal seagrass meadows also occur close to the mainland including Lugger Bay approximately 10 km south of Mission Beach.
The overall grade for the South zone in 2021-22 remained ‘moderate’ and the score increased from 51 to 53 since the previous year.
The diagram below shows the detailed results for each indicator by year. Click on the timeslider to see data from previous years.
The water quality grade in 2021-22 for the South inshore zone remained ‘moderate’ and scored 60, increasing from 52 in 2020-21.
Water quality grades are based on water quality guideline trigger values established for the waters of the Great Barrier Reef Marine Park that, if exceeded, identify the need for management responses. The guidelines are not targets or assessments of pollutant loads entering the marine environment. The results are derived from in-situ water samples taken at six locations and from water quality loggers at two locations from inshore waters extending from sites to the north of Kurrimine Beach to the south of Tully Heads.
The water clarity score increased from 62 in 2020-21 to 65 and the grade remained ‘good’, and is comprised of total suspended solids (‘good’) and turbidity (‘good’).
Nutrients scored 39 increasing substantially from 21 in 2020-21 whilst the grade remained ‘poor’. Nutrients are comprised of oxidised nitrogen (NOx), which improved substantially from ‘very poor’ to ‘moderate’, particulate nitrogen (PN), which remained ‘very poor’, and particulate phosphorus (PP) which improved from ‘moderate’ to ‘good’. The chlorophyll a score of 75 was unchanged since the previous year and the grade remained ‘good’.
There were spatial patterns associated with concentrations of sediment, nutrient and chlorophyll a, and river discharge. The highest concentrations occurred near the mouth of the Tully River and decreased with distance away. These patterns have been strongest in wetter years (e.g. 2018-19).
Pesticide scores for 2020-21 were not available due to the suspension of pesticide logger deployment in the South zone.
In the South inshore zone the overall coral condition score of 60 declined slightly from 61 in 2020-21 and the grade declined from ‘good’ to ‘moderate’.
The coral grade is comprised of the density of juvenile hard corals score of 67 (‘good’), the macroalgae cover score of 40 (‘poor’), the coral cover score of 54 (‘moderate’), the change in coral cover score of 64 (‘good’), and the coral community composition score of 75 (‘good’).
Coral cover increased slightly at all sites, although juvenile density decreased with the transition of juveniles to adults. The macroalgae score improved slightly but the indicator remains ‘poor’ with persistent high macroalgae cover at several sites. Coral communities in the South zone were severely impacted from tropical cyclones Larry (2006) and Yasi (2011), which substantially reduced coral cover. During the regeneration of coral cover reefs are at greater risk of colonisation by macroalgae.
More information on recent changes in coral indicators and the relationships with environmental conditions are provided in the latest Marine Monitoring Program inshore coral report.
The overall seagrass condition for the South zone in 2021-22 remained ‘poor’ with the score remaining 40 since the previous year.
The Marine Monitoring Program updated the indicators for assessing seagrass condition for 2020-21 onwards. The seagrass indicators have changed with the removal of tissue nutrient status and the replacement of the reproductive effort with a more holistic resilience indicator. Information on these updates is available in the methods and results technical reports available here.
The seagrass grade is comprised of abundance which scored of 28 (‘poor’), and resilience score of 48 (‘moderate’) from the Marine Monitoring Program. Missionary Bay seagrass cover reduced from 100% to 63%. Seagrass condition remained ‘very poor’ at Lugger Bay, whilst condition across Dunk Island sites improved slightly. Overall resilience increased from ‘poor’ to ‘moderate’ due to a ‘very good’ score at a Dunk Island intertidal site.
More information on seagrass condition in the South zone is available from the Marine Monitoring Program reports.
The fish index is currently under development and will be available in future report cards.