ENVIRONMENTAL
RESULTS
AREA: 39.19 km2
ABOUT THE ZONE
The Western Basin is located near the north-western end of Gladstone Harbour. Three large-scale Liquid Natural Gas (LNG) plants have been constructed on the south-western shore of Curtis Island. The first of these commenced operation in late 2014. Large industrial plants located on the western shore of this zone include Queensland Energy Resources, Rio Tinto Yarwun, Orica, Transpacific Waste and Cement Australia. Areas of mangroves and mudflats remain between Fisherman’s Landing and the Wiggins Island Coal Export Terminal (WICET) and on the southern tip of Curtis Island.
This zone has six water and sediment monitoring sites, six monitored seagrass meadows, one fish monitoring site, and two mangrove monitoring sub-zones.
WATER & SEDIMENT
The Western Basin received an overall water quality score of 0.78 (B).
Sediment quality of The Western Basin was very good with an overall score of 0.99 (A).
The following graphs compare the Water and Sediment scores reported for 2023 (top line) to those from the previous year.
WATER
SEDIMENT
Very good (0.85-1.00)
Poor (0.25-0.49)
Good (0.65-0.84)
Satisfactory (0.5-0.64)
Very Poor (0.00-0.24)
No data available
Overall, Water quality in the Western Basin scored 0.78 and received a good grade (B), similar to the 2022 report card. This score was calculated by aggregating the three sub-indicator and associated measure scores (Physiochemical – pH and turbidity, Nutrients – total nitrogen, total phosphorus and dissolved metals, and dissolved metals – aluminum, copper, lead, manganese, nickel and zinc).
Within the Physiochemical sub-indicator, Western Basin received a score of 1.00 and a very good grade (A) for pH indicating that the average pH was well below the guideline value. This zone received a score of 0.58 and a satisfactory grade (C) for turbidity indicating that average turbidity was within the guideline value.
Within the Nutrient sub-indicator group all three measures, total nitrogen (0.56) total phosphorus (0.58) and chlorophyll-a (0.50) had satisfactory grades (C), indicating that average concentrations for these measures were within the guideline values for this zone.
All six Dissolved metals received high scores (1.00) and very good grades (A) indicating that average concentrations were well below the water quality guideline values.
For Sediment quality, the Western Basin received an overall score of 0.99 and a very good grade (A), also a similar result to the previous year. This score was calculated by aggregating one sub-indicator and associated measure scores (Metal and metalloids – arsenic, cadmium, copper, lead, mercury, nickel and zinc).
In 2023, all seven of the Metal and metalloids sub-indicator measures received very high scores (0.95–1.00) and very good grades (A), indicating that average concentrations were below the guideline values for this zone.
HABITATS
SEAGRASS RESULTS
Meadow 4
Meadow 6
Meadow 8
Meadow 5
Meadow 7
Meadow 52-57
The Western Basin includes six monitored seagrass meadows, five of which are intertidal and one subtidal (Meadow 7).
In 2023, this zone scored an overall score of 0.72 and received a good grade (B) for the fifth consecutive year. While biomass and area scores for Meadows 4, 5 and 6 were similar to the 2022 report card, a marked decline was seen in species composition scores. In Meadows 7 and 8 the biomass and species composition scores remained similar to the previous year. However, the area scores for meadows 7 and 8 decreased and resulted in a lower grade (satisfactory, C). Consistent with the 2022 report card, Meadow 52–57 received the highest scores and in 2023 was the only meadow in Western Basin to be graded very good (A) overall.
MANGROVE RESULTS
No mangrove assessment was conducted in 2023, results are from monitoring conducted in 2019. The overall zone score for the Western Basin was 0.51 (C) indicating a satisfactory condition. While mangrove extent (0.76) received a good score, both canopy condition (0.39) and shoreline condition (0.37) had poor scores.
The overall score for Western Basin fell from 0.57 in 2018 to 0.51 in 2019. This was largely a result of changes in canopy condition where the score declined from 0.60 in 2018 to 0.39 in 2020. This may reflect the impacts off decreased rainfall over the reporting year.
FISH & CRABS
FISH RECRUITMENT RESULTS
The Fish indicator is comprised of two sub-indicators, Fish Health and Fish Recruitment.
Fish recruitment was assessed for two species: Yellowfin bream Acanthopagrus australis and Pikey bream Acanthopagrus pacificus. The overall score for 2023 was lower than the previous year (2022: 0.98, 2023: 0.77) and declined one grade to good (B). This decline in score is a result of a decrease in number of bream caught during the 2022–23 reporting period
(2022 report card: 67 fish, 2023 report card: 25 fish).
Fish health is assessed though two sub-indicators, Fish condition and Fish Health Assessment Index (HAI).
The overall score for Fish health in 2023 was 0.81 and received a good grade (B). The 2023 results were calculated by the average of the Fish HAI score (0.90; results carried over from 2021) and new assessment of Fish condition which scored similar to the previous year (2022: 0.74, 2023: 0.73).