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.

Grading

gradesa1

very good

gradesb1

good

gradesc1

moderate

gradesd1

poor

gradese1

very poor

insufficient data

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

confidence

Water quality

Hover over each segment for indicator scores and data confidence.

The overall water quality grade in 2015-16 for Trinity Inlet estuary is ‘very 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 71.3 (‘good’) is comprised of a dissolved oxygen (DO) score of 52.6 (‘moderate’) and a turbidity score of 90 ('very good')meaning that the annual median and at least 80% of monthly medians of turbidity comply with guideline values.

Nutrients scored 90 (‘very good’) in Trinity Inlet estuary, comprising of a DIN (dissolved inorganic nitrogen) score of 90 (‘very good) and FRP (filterable reactive phosphorus) score of 90 (‘very good’), meaning that the annual median and at least 80% of monthly medians for both DIN and FRP concentrations comply with guideline values.

The chlorophyll a score in Trinity Inlet estuary is 90 (‘very good’) meaning that that the annual median and at least 80% of monthly medians of chlorophyll a concentrations comply with guideline values.

Pesticides are not monitored in Trinity Inlet therefore a score and grade cannot be provided.

Compared to 2014-15 the water quality index for Trinity Inlet increased from ‘good’ to ‘very good’ due to an increase of the chlorophyll a score from 67.9 (‘good’) to 90 (‘very good’) despite the decline of the DO score from 64.7 (‘good’) to 52.6 (‘moderate’).

Habitat and hydrology

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

The mangrove and saltmarsh extent scored 53.5 (‘poor’) with 20.6% loss from pre-clear to 2013. The riparian extent scored 57.6 (‘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 score is 21.7 (‘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. Whilst the seagrass condition score has declined slightly in Trinity Inlet since 2014-15 and has remained ‘poor’, two indicators (biomass and species composition) have improved from ‘moderate’ to ‘good’.

Estuary fish barriers for Trinity Inlet are scored 61 (‘good’) and are graded 'moderate’ for barrier density, ‘moderate’ for percentage of stream length to the first barrier, with an absence of low passability barriers (graded ‘very good’).

Estuary riparian extent, mangrove and saltmarsh extent and estuary fish barriers are updated every four years. The data for riparian extent, mangrove and saltmarsh extent is to be updated in 2018.

The method for the flow indicator is currently under development and will be available for future report cards.

Fish

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.