The northern boundary of the North Inshore reporting zone extends north-eastward from the mainland just north of the Bloomfield River along the boundary of the Wet Tropics NRM marine region to the boundary of the offshore waters and includes enclosed coastal, open coastal and mid-shelf waters.
The southern boundary of the North zone extends north-east from Cape Grafton just south of Cairns to the offshore boundary. The major rivers discharging into the North zone are the Daintree River, the Mossman River and the Barron River.
The Bloomfield River discharges at the northern most extent and Smiths Creek discharges through Trinity Inlet at the southernmost extent. Numerous smaller waterways draining the catchments of the often steep eastern slopes of the Great Dividing Range also discharge into the North zone.
Water quality in the North 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 Russell/Mulgrave and the Tully/Murray, which are carried north by prevailing currents.
The area includes Snapper Island, some 3.7 km east of the Daintree River mouth, the low Isles 11km south-east of Snapper Island, and Green Island, approximately 27 km north east of Cairns. These islands provide fringing shallow water environments that support coral reef ecosystems and intertidal reef seagrass meadows. Subtidal and intertidal coastal seagrass meadows also occur close to the mainland including Cairns Harbour and Yule Point approximately 10km south of Port Douglas.
The diagram below shows the detailed results for each indicator by year. Click on the timeslider to see data from previous years.
Water quality in the North inshore zone is graded ‘good’ in 2016-17 with a score of 69.
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 from inshore waters extending from sites adjacent to Cape Tribulation in the north to sites adjacent to Cairns in the south and from passive pesticide samplers located at the Low Isles.
The water clarity score of 69 (‘good’) in the North zone is comprised of a total suspended solids (TSS) score only. Turbidity was not monitored in the North Zone.
Nutrients scored 68 (‘good’) in the North zone, comprising of ‘very good’ for oxidised nitrogen (NOx), a ‘moderate’ for particulate nitrogen (PN) and a ‘moderate’ for particulate phosphorus (PP).
The chlorophyll a score in the North zone is 47 (‘moderate’).
Using the Photosystem II herbicide equivalent concentrations method, pesticides received a score of 93 (‘very good’).
The water quality index score in North zone changed from 79 in 2015-16 to 69 with the largest decreases occurring for chlorophyll a and PN.
The overall coral grade for the North inshore zone in 2016-17 is ‘moderate’ with a score of 46.
The coral grade is comprised of the density of juvenile hard corals score of 40 (‘poor’), the macroalgae cover score of 40 (‘poor’), the coral cover score of 42 (‘moderate’), the change in coral cover score of 67 (‘good’), and the coral community composition score of 42 (‘moderate’).
The coral index grade in the north zone has remained ‘moderate’ since 2014-15 and the index score of 46 remains unchanged from 2015-16.
In the North zone the impacts of the 2017 bleaching event differed considerably between sites although the combined results for the zone showed a halt to the increases for the coral index score between 2014-15 and 2015-16. An increase in macroalgae cover (as represented in decline in the macroalgae score) may indicate high nutrient availability as a factor limiting coral community condition at Snapper Island.
More information is available in the Marine Monitoring Program inshore coral report by Thompson et al. (2018).
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.