Trinity Inlet

The area of the Trinity Inlet estuary reporting zone can be defined by the pre-cleared extent of mangrove and saltmarsh remnant vegetation which is characterised by species that require periodic inundation of sea water.

This area extends approximately 14 km inland south of the inlet’s mouth and is approximately 8 km in width. It includes numerous tributaries that drain into Trinity Inlet.

Land use within and adjacent to the Trinity estuary area includes residential, industrial and commercial developments associated with the central business district of Cairns.

Trinity inlet includes the Port of Cairns which is a multi-purpose port that caters for bulk cargo cruise shipping, fishing vessels and reef passenger vessels. Land use adjacent to the smaller upstream tributaries is dominated by cropping (sugarcane) with some residential development.

Key results for 2024-25

The Trinity Inlet estuary grade remained ‘moderate’ in 2024-25 and the score increased from 55 to 58 since the previous year.

• Water quality improved from ‘moderate’ to ‘good’ with the score increasing from 59 to 65.
• Turbidity remained ‘very good’. 
• Dissolved oxygen remained ‘poor’.
• Dissolved inorganic nitrogen (DIN) improved from ‘moderate’ to ‘good’. 
• Filterable reactive phosphorus (FRP) declined from ‘very good’ to ‘good’.
• Chlorophyll a improved from ‘moderate’ to ‘good’.
• Mangrove and saltmarsh extent remained ‘moderate’ with no recorded habitat loss since 2019.
• Riparian vegetation extent remained ‘moderate’ with no recorded habitat loss since 2019.
• Seagrass condition in Trinity Inlet remained ‘poor’ with the score increasing from 25 to 28. Whilst biomass improved at two meadows, there was a complete loss of the intertidal meadow.

The diagram below shows the detailed results for each

indicator by year. Click on the timeslider to see data from previous years.