Port Curtis and Rodds Bay seagrass monitoring program, November 2010

Chartrand, K.M., McCormack, C.V., and Rasheed, M.A. (2011) Port Curtis and Rodds Bay seagrass monitoring program, November 2010. Report. Department of Employment, Economic Development and Innovation, QLD, Cairns, QLD, Australia.

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This report details the findings of the 2010 annual seagrass monitoring survey for Port Curtis and Rodds Bay and seasonal mapping of seagrasses within the Western Basin region of the port. The report integrates 2010 survey data with previous long-term monitoring assessments conducted since 2002, assessing seagrass meadow area, biomass and species composition. The 2010 survey included assessments of intertidal and shallow subtidal meadows in the Western Basin region from The Narrows to Boyne River as well as long-term monitoring meadows located in Rodds Bay. This survey was part of the Port Curtis Integrated Monitoring Program (PCIMP) and a bi-annual assessment of inner harbour seagrasses undertaken since November 2009 as a part of increased monitoring for planned harbour expansion and dredging programs.

Compared to the broad distribution of meadows mapped in the 2009 whole of port baseline reassessment, the November 2010 survey found a significant reduction in total area and biomass of seagrass throughout the Western Basin region. While the majority of seagrass loss was in the subtidal meadows, many intertidal meadows were reduced in density and abundance from previous years. In addition, some intertidal meadows where dugong feeding trails were consistently recorded in previous surveys had substantially reduced in seagrass coverage with no signs of recent feeding activity in November 2010.

In 2010, seagrass meadows that have been monitored annually since 2002 were in a more susceptible condition relative to previous years. Total distribution of the fifteen monitoring meadows (including the new monitoring meadows in the Narrows and surrounding the Channel Islands) was approximately 42% lower in 2010 from 2009 estimates. Specific concerns were those meadows absent in 2010 including the Fishermans Landing subtidal meadows and an intertidal South Trees meadow adjacent to major port facilities. Other intertidal meadows that had also contracted in distribution and abundance were uncharacteristic from previous assessments.

The major driver of seagrass change is likely to be climate related as similar declines have been observed state-wide following a significant wet season in late 2009 to early 2010. Rainfall, river flow and elevated temperature are suggested as the major drivers of seagrass dynamics in the Port Curtis area. Should climate conditions become more favourable to seagrass growth we would expect to see recovery of these seagrass meadows.

Since late 2009, assessments of light and temperature have begun to provide information on in situ conditions to evaluate changes occurring at the meadow scale. Long-term collection of such data within meadows will enhance the effectiveness of the monitoring program by distinguishing some natural versus anthropogenic drivers of seagrass change. Low light levels within a number of meadows suggest seagrass may already be subject to low light stress reducing their potential resilience to future impacts. The light data collected during 2010 supports a reduction in available light being one of the primary causes of seagrass decline.

The loss of some meadows, together with potential water quality issues have left the seagrasses of Port Curtis in a condition where they may be vulnerable to additional stresses including those associated with dredging. A more complete understanding of the environmental requirements of seagrasses in Port Curtis is being developed as part of additional seagrass studies connected with the Western Basin development (Chartrand et al. 2010). These studies will help to accurately inform environmental management of future developments.

Item ID: 45226
Item Type: Report (Report)
Keywords: recovery, resilience, management, environmental monitoring, marine monitoring, marine water quality, seagrass, reproduction, seagrass habitats, Great Barrier Reef, port development, dredging
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Funders: Gladstone Ports Corporation Limited
Date Deposited: 31 Aug 2016 03:38
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050206 Environmental Monitoring @ 50%
05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050205 Environmental Management @ 50%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960503 Ecosystem Assessment and Management of Coastal and Estuarine Environments @ 50%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 50%
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