Inshore South

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 2019-20 remained ‘moderate’ with the score increasing from 47 to 56.

The diagram below shows the detailed results for each indicator by year. Click on the timeslider to see data from previous years.

Water quality

The water quality grade in 2019-20 for the South inshore zone improved from ‘moderate’ to ‘good’ and scored 72, increasing from 44 in 2018-19.

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 ten 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. In addition, passive pesticide samplers are located at Dunk Island.

The water clarity score increased to 82 (‘very good’) from 54 (‘moderate’) in 2018-19 and is comprised of total suspended solids (very good) and turbidity (‘good’).

Nutrients scored 42 (‘moderate’) increasing substantially from 7 (‘very poor’) in 2018-19. Nutrients are comprised of oxidised nitrogen (NOx) graded ‘poor’, particulate nitrogen (PN) graded ‘poor’ and particulate phosphorus (PP) graded ‘moderate’.

In contrast to 2018-19, there were no strong seasonal and spatial patterns associated with river discharge and nutrient concentrations during the considerably drier conditions of 2019-20.

The chlorophyll a score in the South zone improved from 24 (‘poor’) in 2018-19 to 71 (‘good’).

Using the pesticide risk metric pesticides were graded ‘very good’ and scored 91, equating to greater than 99 percent of species protected.

Coral

The overall coral condition score of 62 with a grade of ‘good’ in 2019-20 for the South inshore zone was unchanged from the previous year.

The coral grade is comprised of the density of juvenile hard corals score of 78 (‘good’), the macroalgae cover score of 44 (‘moderate’), the coral cover score of 46 (‘moderate’), the change in coral cover score of 74 (‘good’), and the coral community composition score of 75 (‘good’).

The improved score and grade for the South zone was driven by increases for all indicators except for macroalgae cover. The score for species composition had the largest increase, from 58 to 75, and coral cover also improved.

Coral communities in the South zone were severely impacted from tropical cyclones Larry and Yasi, which substantially reduced coral cover. During the regeneration of coral cover reefs are at greater risk of colonisation by macroalgae. Within this zone the reefs in closest proximity to river discharge and the nutrient rich waters released from the Tully and Herbert Rivers have higher cover of macroalgae and have shown less recovery in coral condition compared to the reefs further from the river mouths.

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.

Seagrass

The overall seagrass grade in for the South zone remained ‘poor’ with the score unchanged at 35.

The seagrass grade is comprised of the percent cover score of 19 (‘very poor’), the tissue nutrient score of 36 (‘poor’), and reproductive effort score of 38 (‘poor’) from the Marine Monitoring Program.

Overall site scores were similar to the previous year at Lugger Bay and Dunk Island intertidal. For Dunk Island subtidal, overall condition improved from ‘very poor’ to ‘poor’, whilst for Missionary Bay, overall site condition declined from ‘very good’ to ‘good’.

Percent cover declined from ‘poor’ to ‘very poor’across all sites, whilst reproductive effort and tissue nutrient condition improved from the previous year.

More information on seagrass condition in the South zone is available from the Marine Monitoring Program reports. 

Fish

The fish index is currently under development and will be available in future report cards.

 

References

Thompson A, Costello P, Davidson J, Logan M, Greg Coleman (2019) Marine Monitoring Program. Annual Report for inshore coral reef monitoring: 2017 to 2018. Australian Institute of Marine Science, Townsville.132 pp. 

 

See the detailed reports for further information on the methods used to produce the scores and grades and detailed results