Port Curtis benthic primary producer habitat assessment and health studies update: interim report December 2010

Chartrand, K.M., McKenna, S.A., Petrou, K., Jimenez-Denness, I.M., Franklin, J., Sankey, T.L., Hedge, S.A., Rasheed, M.A., and Ralph, P.J. (2010) Port Curtis benthic primary producer habitat assessment and health studies update: interim report December 2010. Report. Department of Employment, Economic Development and Innovation (DEEDI), Cairns, QLD, Australia.

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This interim report provides an update on the Benthic Primary Producer Habitat Assessment and Seagrass Health Studies programs in Port Curtis and Rodds Bay from November 2009 to December 2010. It integrates the multi-faceted monitoring and research program formed from a collaboration between Fisheries Queensland, Vision Environment and Queensland Gas Corporation (QGC) in preparation for the development of a large scale dredging operation for a liquefied coal seam gas port facility on Curtis Island. Many components of this study are still underway and as such results for these are preliminary and are likely to be further refined at the conclusion of experimental work. Full results will be available as part of the final report at the conclusion of experimental studies.

In order to develop effective predictive models of impact to seagrasses and appropriate dredge mitigation strategies to minimise the impacts, information on the distribution, light requirements, tolerances and ability to recover for the various seagrass communities in Gladstone is required.

The major outcomes from the program (to date) developed to address these questions are outlined below:

• Based on early results of the program a light requirement trigger for seagrasses in Port Curtis of 12 mol m⁻² d⁻¹ over a rolling two week period is suggested. This value could be used year round as a conservative approach to light requirements.

• Results from winter experiments suggest light requirements at this time of year may be significantly lower. The light requirement trigger will be further refined with further results from experimental program underway.

• Seagrass distribution and abundance was significantly lower during the winter re-survey of the Western Basin compared to the summer baseline in November 2009. This result is typical of the natural seasonal dynamics found in tropical Queensland seagrass meadows (Carruthers et al. 2002).

• Seagrasses in Port Curtis appear to exist in a low light, nutrient rich and nitrogen limiting environment. Quarterly monitoring found seagrass meadow nutrient dynamics to also follow typical seasonal patterns corresponding to summer (wet) and winter (dry) shifts.

• Reproductive potential and productivity (growth) rates measured over the previous 12 months provides a means to assess seagrass species' potential resilience to future 2 environmental and habitat change. Initial trends are limited, however, a larger dataset will provide more detailed information on Gladstone seagrass productivity over the next year.

• Simulated light reduction during in situ shading experiments found a much smaller effect on all Gladstone seagrass species in the winter than during summer studies.

• Pigment characterisation during shading studies found that the violaxanthin deepoxidation state may act as the best sub-lethal indicator tool out of those tested, however further analysis and testing during lab manipulation studies is needed to further develop and assess its applicability for dredge mitigation and management of seagrass.

• Conclusions from the tidal exposure study are limited as only one sampling event had taken place at the time of production of this interim report (November 2010). From this study, however, seagrass appeared high-light adapted but with consistent declines in photosynthetic activity with air-exposure. This finding highlights the sensitivity of these intertidal species to desiccation which has major implications with respect to their daily productivity.

• The initial spectral profiling of Gladstone Harbour during both pre-dredge and con-dock dredging detected a significant "yellow-shift" in the spectral quality of light at 2.0m. Lab manipulation experiments will provide a clearer understanding of what impact this shift has on seagrass physiology and associated light demands.

The environmental requirements and impacts of potential light reductions from large scale dredging to Port Curtis seagrasses will be refined as background monitoring data and seagrass health studies are completed. A final report on the shading study results as well as ongoing seagrass health studies projects will be provided in July 2011. Other significant results that are completed prior to this time will be presented as they become available and as part of an interim update in March 2011.

Item ID: 39928
Item Type: Report (Report)
Keywords: seagrass habitats, port management, recovery, resilience, dredging, marine monitoring, environmental monitoring
Funders: Gladstone Ports Corporation (GPC), Qld Department of Employment, Economic Development and Innovation (DEEDI)
Projects and Grants: DEEDI Marine Ecology Group (MEG)
Date Deposited: 25 Aug 2015 05:47
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050205 Environmental Management @ 50%
05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050206 Environmental Monitoring @ 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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