Inshore Central

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

Water quality

Water quality is graded 'moderate' in the Central inshore zone for 2016-17 with a score of 58.

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 51 (‘moderate’) in the Central zone is comprised of total suspended solids (‘moderate’) and turbidity (‘good’).

Nutrients scored 50 (‘moderate’) in the Central zone, comprising of ‘poor’ for oxidised nitrogen (NOx), a ‘moderate’ for particulate nitrogen (PN) and a ‘good’ for particulate phosphorus (PP).

The chlorophyll a score in the Central zone is 52 (‘moderate’).

Using the Photosystem II herbicide equivalent concentrations method, pesticides received a score of 80 (‘good’).

The water quality index grade in the Central zone has changed from ‘good’ in 2015-16 to ‘moderate’ with decreases in the scores for NOx, PN and chlorophyll a.


The overall coral grade for the Central inshore zone in 2016-17 is 57 (‘moderate’).

The coral grade is comprised of the density of juvenile hard corals score of 30 (‘poor’), the macroalgae cover score of 76 (‘good’), the coral cover score of 58 (‘moderate’), the change in coral cover score of 80 (‘good’), and the coral community composition score of 42 (‘moderate’).

Since 2014-15 the coral index in the Central zone has remained as a ‘moderate’ grade and the score has declined slightly from 60 in 2015-16 to 57 this year.

During 2016-17 the coral reefs in the Central zone were affected by continued pressure from Crown-of-Thorns starfish (COTS) activity and the impacts from coral bleaching. On reefs without COTS a substantial increase in coral cover occurred before the 2017 bleaching event. This increase contributed to the high scores for the coral change indicator and offset the loss of cover observed as a result of bleaching which helped maintain a coral index grade of moderate.

Further information about recent changes in the coral index for the central zone are available from the latest Marine Monitoring Program coral report (Thompson et al. 2017).


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

Further information on the methods used to produce the scores and grades and detailed results can be found here.