The northern boundary of the Central inshore reporting zone area extends north-east from Cape Grafton just south of Cairns to the offshore boundary and includes enclosed coastal, open coastal and mid-shelf waters.
The southern boundary of the Central zone extends due eastward from the mainland just south of the Moresby River at Double Point to the boundary of the offshore waters.
The major rivers discharging into the central zone are the Mulgrave River the Russell River and Johnstone River. The Moresby River discharges into the southern coastal area of the Central zone. Numerous smaller waterways drain coastal sub catchments that discharge into the Central zone.
Water quality in the Central zone is affected by plumes of sediments, nutrients and pesticides from rivers discharging directly into the zone but also from the plumes of southern rivers, particularly the Tully/Murray, which are carried north by prevailing currents.
The area includes Fitzroy Island to the north, the High Island Group some 12km north-east of Deeral, the Frankland Island group approximately 16 km due east of Deeral and Normanby Island located between the High Island group and the Frankland Island group. These islands provide fringing shallow water environments that support coral reef ecosystems.
The overall grade for the Inshore Central zone improved from ‘moderate’ to 'good' in 2019-20 with the score increasing form 59 to 67.
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 2019-20 for the Central inshore zone improved from ‘moderate’ to ‘good’ and scored 74, increasing from 58 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 four locations from inshore waters extending from sites at Fitzroy Island in the north to sites at the Frankland Island Group in the south. In addition, passive pesticide samplers are located at High Island.
The water clarity score of 89 (‘good’) increased from 70 (‘good’) in 2018-19. Water clarity is comprised of total suspended solids (‘very good’) and turbidity (‘good’).
Nutrients scored 43 (‘moderate’) and increased from 21 (‘poor’) in 2018-19. Nutrients are comprised of oxidised nitrogen (NOx) graded ‘very poor’, particulate nitrogen (PN), graded ‘ moderate’ and particulate phosphorus (PP) graded ‘good’. 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 Central zone increased from 51 in 2018-19 to 75 and the grade improved from ‘moderate’ to ‘good’.
Using the pesticide risk metric pesticides were graded ‘very good’ and scored 89, equating to greater than 99 percent of species protected.
The overall coral grade in 2019-20 for the Central inshore zone was 61 (‘good’) and increased from 60 (‘moderate’) in 2018-19.
The coral grade is comprised of the density of juvenile hard corals score of 40 (‘poor’), the macroalgae cover score of 65 (‘good’), the coral cover score of 74 (‘good’), the change in coral cover score of 64 (‘good’), and the coral community composition score of 61 (‘good’).
The Central zone has had improvement of coral cover and composition over the last several years, particularly on shallow reefs. The continued moderate density of crown-of-thorns starfish at some sites (High Island, Fitzroy Island and in the Frankland Group) will have impacted the rate of coral cover increase despite rapid growth of fast-growing corals in recent years.
Further information about recent changes in the coral index for the central zone are available from the latest Marine Monitoring Program inshore coral report.
There is currently no seagrass monitoring undertaken in the Central zone and consequently no seagrass grade can be calculated for this zone.
The fish index is currently under development and will be available in future report cards.