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 remained ‘moderate’ with the score increasing from 48 in 2016-17 to 54.
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 2017-18 for the North inshore zone remained ‘good’ and scored 66.
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 an 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 52 (‘moderate’) in the North zone is comprised of a total suspended solids (TSS) score only. Turbidity was not monitored in the North Zone.
Nutrients scored 70 (‘good’) in the North zone, comprising of ‘very good’ for oxidised nitrogen (NOx), a ‘good’ for particulate nitrogen (PN) and a ‘poor’ for particulate phosphorus (PP).
The chlorophyll a score in the North zone was 49 (‘moderate’).
Using the pesticide risk metric pesticides were graded “very good” and scored 92, equating to 99.6 percent of species protected.
The overall coral grade in 2017-18 for the North inshore zone is ‘moderate’ and scored 51. The coral index grade in the north zone has remained ‘moderate’ since 2014-15.
The coral grade is comprised of the density of juvenile hard corals score of 40 (‘poor’), the macroalgae cover score of 49 (‘moderate’), the coral cover score of 45 (‘moderate’), the change in coral cover score of 70 (‘good’), and the coral community composition score of 50 (‘moderate’).
The North zone score improved in 2017-18 since the previous two years mostly due to improved indicators for coral cover and composition associated with the growth of corals in shallower water. The score for the juvenile density indicator remained low with a grade of ‘poor’. This was primarily due to very low scores for juvenile density at Snapper Island sites and is the main limiting factor for condition scores in the North zone.
More information is available in the Marine Monitoring Program inshore coral report by Thompson et al. (2019).
The overall seagrass grade in 2017-18 for the North inshore zone increased from ‘poor’ in 2016-17 to ‘moderate’ with the score increasing from 30 to 46.
The seagrass grade is comprised of the seagrass percent cover score of 48 (‘moderate’), the tissue nutrient score of 35 (‘poor’), and reproductive effort score of 38 (‘poor’) from the Marine Monitoring Program in addition to the seagrass biomass score of 54 (‘moderate’), the meadow area score of 75 (‘good’), and seagrass species composition score of 76 (‘good’) from the Queensland Ports Seagrass Monitoring Program.
Key messages on the coral condition for the North Inshore zone include the following.
- Coastal sites and meadows showed considerable signs of improvement and recovery in recent years, particularly for indicators related to seagrass abundance such as biomass, percent cover and meadow area.
- Species composition in coastal monitoring meadows has largely returned to a pre-disturbance state (good condition).
- The Cairns Zostera muelleri seed bank improved in 2017-2018 indicating improved meadow resilience. Importantly, 50% of seeds in the seed bank were viable, the first time that viable seeds have been recorded since June 2015.
- Reproductive effort also improved at MMP sites, from no reproductive effort recorded across all inshore sites in 2016-2017.
The fish index is currently under development and will be available in future report cards.
Thompson A, Costello P, Davidson J, Logan M, Greg Coleman (2019) Marine Monitoring Program. Annual Report for inshore coral reef monitoring: 2017 to 2018. Australian Institute of Marine Science, Townsville.132 pp.