Gladstone Healthy Harbour Partnership 2017 Report Card, ISP011: seagrass

Carter, Alex, Wells, Jaclyn, and Rasheed, Michael (2017) Gladstone Healthy Harbour Partnership 2017 Report Card, ISP011: seagrass. Report. James Cook University, Cairns, QLD, Australia.

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Seagrass condition was assessed for 14 monitoring meadows across six Gladstone Healthy Harbour Partnership (GHHP) reporting zones in November 2016 (GHHP 2017 reporting year).

Seagrass condition in the Gladstone Harbour region remained poor (D, 0.39) in the 2017 reporting year.

Survey results were mixed for individual meadows and zones within the survey area. The overall score for each meadow is the lowest of the three indicator scores. Area determined the overall meadow score in seven of the monitoring meadows, species composition in four meadows, and biomass in three meadows.

Seagrass condition improved in The Narrows (poor to satisfactory), South Trees Inlet (poor to good), in the Passage Islands meadow (satisfactory to good) and two Wiggins Island meadows (satisfactory to good, and poor to satisfactory) in the Western Basin Zone, and at Quoin Island (poor to satisfactory) in the Mid Harbour.

Seagrass condition declined in Rodds Bay (poor to very poor), in the meadow immediately north (poor to very poor) and two meadows to the south (good to poor, and good to satisfactory) of Fishermans Landing in the Western Basin Zone, and at Pelican Banks (poor to very poor) in the Mid Harbour. Condition remained very poor in the Inner Harbour.

Condition declines in the Pelican Banks meadow - the largest and most stable seagrass meadow in the Gladstone region - is concerning. The meadow is now in very poor condition, driven by the lowest ever recorded biomass. Meadow area and percent composition of the dominant species Z. muelleri subsp. capricorni were also at record lows. The reasons for these declines are unclear. Light monitoring indicated favourable conditions for seagrass growth in 2016, daytime tidal exposure had reduced from 2015, and there were far fewer instances of water temperatures occurring above 33oC for extended periods of time than in 2015. Potential contributors to the decline include high levels of dugong and turtle herbivory, sediment changes, and cumulative impacts of multiple stressors over multiple years, but require further investigation.

Environmental conditions influence seagrass condition in Gladstone. Years where >50% of meadows were assigned an overall meadow condition of poor or very poor either correspond with (2010-2016) or directly follow (2004) periods of above average rainfall and river flow in the region. There was no cyclone-related flooding in the 12 months preceding the November 2016 survey, however total monthly rainfall was above the long-term (1958-2016) average in March, June, July and September 2016. Calliope River flow also peaked above the long-term (1970-2016) average in February and July 2016, but otherwise was below or close to the long-term average leading up to the November 2016 survey. High rainfall and flooding of the Fitzroy and Calliope Rivers associated with Tropical Cyclone Debbie in March 2017 may further impact seagrass condition in 2017.

There was no sign of seagrass recovery at the Gladstone Harbour scale from the previous year. Resilience of seagrasses to further natural or anthropogenic impacts in the Gladstone Harbour region is likely to be low.

This report is presented into two parts. Part 1 summarises report card results for the annual survey. Part 2 is an accompanying technical report that details methods, analysis, results and interpretation.

Item ID: 70853
Item Type: Report (Report)
Keywords: seagrass, Gladstone, Gladstone Healthy Harbour Partnership, report card
Copyright Information: © James Cook University, 2017.
Funders: Gladstone Healthy Harbour Partnership
Date Deposited: 16 Nov 2021 23:34
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring @ 100%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1802 Coastal and estuarine systems and management > 180201 Assessment and management of coastal and estuarine ecosystems @ 100%
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