Trinity Inlet Estuary

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. The area 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.

Scroll down for further detailed results for each indicator group.



very good








very poor


insufficient data


not applicable

Confidence surrounding the data used in the circle diagrams has been assessed using a multi-criteria framework.


Water quality

Hover over each segment for indicator scores and data confidence.

The overall water quality grade in 2014/15 for Trinity Inlet estuary is ‘good’. Water quality grades are based on aquatic ecosystem guidelines for protection of estuarine waters, and are not based on load reduction targets for the marine environment. The results are derived from a transect of 8 monitoring sites in the main channel of Trinity Inlet.

The physical and chemical score of 100 (good) is comprised of a dissolved oxygen (DO) score of 100 (good) indicating that the annual median of DO complies with guideline values.

Nutrients scored 100 (very good) in Trinity Inlet estuary, comprising of a DIN (dissolved inorganic nitrogen) score of 100 (very good) and FRP (filterable reactive phosphorus) score of 100 (very good), indicating that the annual median and 80% of monthly medians for both DIN and FRP comply with guideline values.

The chlorophyll a score in Trinity Inlet estuary was 100 (good) indicating that that the annual median of chlorophyll-a complies with guideline values.

Habitat and hydrology

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The overall habitat and hydrology grade for Trinity Inlet estuary is ‘poor’.

The mangrove and saltmarsh extent scored 33 (very poor) with 20.6 per cent loss from pre-clear to 2013. The riparian extent scored 91.5 (moderate) with 17.6 per cent loss from pre-clear to 2013. These results reflect the high level of development within the estuary area of Trinity Inlet. The low mangrove and saltmarsh extent scores for Trinity Inlet are mostly the result of historic extensive clearing activity. More recently mangrove communities in the Trinity Inlet estuary have been effectively managed to ensure there has been no major new clearing and to allow for some revegetation.

The seagrass condition scored 41.6 (poor). The low seagrass score is due to the large scale declines in seagrass meadow condition recorded in the 2010-2014 periods across the Wet Tropics predominantly resulting from extreme weather events including storms and cyclones.

Estuary riparian extent and mangrove and saltmarsh extent are updated every four years and the figures in the pilot report card are the most current. The data for both are due to be updated in 2017/18.

The methods for the flow and fish barrier indicators are currently under development and will be available for future report cards.

Note: Seagrass condition score is not calculated as the mean of the indicator scores. The seagrass condition score is calculated from the minimum indicator value at each site and the mean of the site scores. Refer to Wet Tropics Pilot Report Card Methods for more information.


Hover over each segment for indicator scores and data confidence.

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.