ENVIRONMENTAL
RESULTS
ABOUT THE ZONE
The Inner Harbour is located immediately to the east of the Western Basin and is bounded by mangroves on Curtis Island and the town of Gladstone on the southern edge.
WATER & SEDIMENT
The Inner Harbour received an overall water quality score of 0.83 (B).
Sediment quality of the Inner Harbour was very good with an overall score of 0.93 (A).
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The following graphs compare the Water and Sediment scores reported for 2024 (top line) to those from 2023.
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 Inner Harbour (0.83) scored higher than the 2023 report card, however, the overall grade (good, B) remained unchanged. This score was calculated by aggregating the three sub-indicator and associated measure scores (Physicochemical – pH and turbidity, Nutrients – total nitrogen, total phosphorus and dissolved metals, and dissolved metals – aluminium, copper, lead, manganese, nickel and zinc).
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Within the Physicochemical sub-indicator, Inner Harbour received a score of 1.00 and a very good grade (A) for pH, indicating that the average pH was well within the guideline value range. This zone received a score of 0.51 for turbidity, and improved to a satisfactory grade (C) in 2024 from a poor grade (D) in 2023.
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Within the Nutrient sub-indicator, total nitrogen (0.53) had a satisfactory grade (C), indicating that average concentrations for this measure were below the guideline value for this zone. Total phosphorus (0.91) received a very good grade (A), improving a grade from 2023. Chlorophyll- a (0.50) remained a satisfactory grade (C) in 2024.
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All six Dissolved metals received high scores (1.00) and very good grades (A) indicating that concentrations were well below the water quality guideline values.
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For Sediment quality, Inner Harbour received an overall score of 0.93 and a very good grade (A), a similar result to the previous year. This score was calculated by aggregating measure scores (Metal and metalloids – arsenic, cadmium, copper, lead, mercury, nickel and zinc).
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In 2024, six of the seven Metal and metalloid sub-indicator measures received very high scores (0.89–1.00) and very good grades (A) and reflect all concentrations were well below guideline values. One measure – arsenic – received a score of 0.60 and a satisfactory grade (C), indicating that concentrations of arsenic in the Inner Harbour were also below the guideline value.
HABITATS
SEAGRASS (MEADOW 58)
The Inner Harbour zone has one monitored, intertidal meadow in the south-east corner of the zone near South Trees Inlet.
Meadow 58 Seagrass scores showed improvement after steadily declining since 2019. In 2024 Inner Harbour seagrass received an overall score of 0.43, resulting in a poor grade (D). Despite gains in biomass and area scores, the overall condition of the meadow remains poor due to the continued absence of key seagrass species Zostera muelleri, shown by the very poor grade (E) for species composition.
MANGROVE RESULTS
Inner Harbour has two Mangrove monitoring zones – one at Enfield Creek, and another at Barney Point. In 2024, the overall grade for Mangroves at Inner Harbour remained a satisfactory (C). Mangrove extent declined in grade from a satisfactory (C) in 2019 to a poor grade (D) at Inner Harbour in 2024. The grade for canopy condition at Inner Harbour remained a satisfactory (C) in 2024. Shoreline condition of mangroves at Inner Harbour remained a satisfactory (C) grade in 2024.
FISH & CRABS
FISH RECRUITMENT RESULTS
Fish recruitment was assessed for two species: Yellowfin bream (Acanthopagrus australis) and Pikey bream (Acanthopagrus pacificus). Fish recruitment at Inner Harbour improved from a satisfactory grade (C) in 2023 to a good grade (B) in 2024.
MUD CRAB RESULTS
The zone score and grade for Inner Harbour was not calculated in 2023, due to a small number (only four) of mud crabs caught during the monitoring period. The small sample size (less than five) means it was not appropriate to calculate grades for this zone, except for the abundance measure (0.00) in 2023. Higher sample sizes in 2024 allowed for the calculation of sex ratio and prevalence of rust lesion scores, however, the overall grade for Mud crabs at Inner Harbour was poor (D). Prevalence of rust lesions was low, resulting in a high score (0.96) and a very good grade (A) for this sub-indicator in this zone.