Inshore North

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 overall grade for the North zone in 2023-24 declined from ‘good’ to ‘moderate’ and the score decreased from 66 to 59 since the previous year.

Key results

• The water quality grade for the North inshore zone remained ‘very good’ in 2023-24, and the score increased from 82 to 83. Water quality monitoring activities were impeded by the severe weather conditions during December following the landfall of Tropical Cyclone Jasper. This meant that the peak impacts on inshore water quality due to extreme river discharge and flood plumes were not captured by the water sampling.
• For total suspended solids (TSS) the grade improved from ‘good’ to ‘very good’, whilst for all other indicators (chlorophyll a, nutrients (oxidised nitrogen, particulate nitrogen, particulate phosphorus) and pesticide risk) the grades remained the same as the previous year.
• Coral reefs in the North zone were impacted by Tropical Cyclone Jasper due to physical damage from storm waves, and from freshwater inundation as severely flooded waterways discharged into the coastal environment.
• The coral condition index in the North zone remained moderate and score decreased from 54 to 42 since the previous year.
• Freshwater inundation from the Daintree River floods killed all the coral at the Snapper Island South monitoring sites.
• The mean total cover of hard and soft corals in the North zone decreased from 51% the previous year to 21%, and this included cover measured for 2023-24 at the Low Isles before the tropical cyclone event.
• The Macroalgae indicator improved from ‘moderate’ to ‘good’ due to reduced cover of macroalgae at Snapper Island sites, also caused by the freshwater inundation.
• The Juvenile coral indicator declined from ‘poor’ to ‘very poor’ due to the impacts at all Snapper Island reefs.
• Seagrass condition for the North Region declined from ‘good’ to ‘moderate’ since the previous year.
• Seagrass condition at Cairns Harbour meadows were only monitored before Tropical Cyclone Jasper. The average grades for all condition indicators (biomass, area, species composition) were good or very good.
• Seagrass at the other sites had monitoring both before and after Tropical Cyclone Jasper. Impacts from the severe weather conditions were evident at all sites, with seagrass declining in condition across the north zone, with both the abundance and resilience indicators affected.

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