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 Central zone in 2021-22 declined from ‘good’ to ‘moderate’ and the score decreased from 61 to 60 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 2020-21 for the Central inshore zone improved from ‘moderate’ to ‘good’ and scored 62, increasing from 60 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 five 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.

The water clarity score of 76 increased from 75 in 2020-21 and the grade remained ‘good’. Water clarity is comprised of total suspended solids (‘good’) and turbidity (‘good’).

Nutrients scored 45 (‘moderate’) and increased from 37 (‘poor’) in 2020-21. Nutrients are comprised of oxidised nitrogen (NOx), particulate nitrogen (PN), both remaining ‘poor’, and particulate phosphorus (PP) which improved from ‘moderate’ to ‘good’.

The chlorophyll a score decreased from 69 in 2020-21 to 65 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 Russell-Mulgrave rivers 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 Central zone.



The overall coral grade in 2021-22 for the Central inshore zone declined from ‘good’ to ‘moderate’ and the score decreased from 63 to 58.

The coral grade is comprised of the density of juvenile hard corals score of 38 (‘poor’), the macroalgae cover score of 59 (‘moderate’), the coral cover score of 73 (‘good’), the change in coral cover score of 64 (‘good’), and the coral community composition score of 58 (‘moderate’).

In the Central zone high cover of macroalgae at some sites substantially reduced the score for this indicator, whilst coral cover increased and the score for this indicator has risen to its highest value.

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 no current seagrass monitoring undertaken in the Central zone and consequently there is no seagrass grade available for the Central zone.



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


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