Rasheed, M.A., McKenna, S.A., and Tol, S. (2013) Seagrass habitat of Cairns Harbour and Trinity Inlet: annual monitoring and updated baseline survey. Report. TropWATER, James Cook University, Cairns, QLD, Australia.

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Abstract

Key Findings:

• Seagrasses in Cairns have undergone unprecedented declines over the past 3 years and are at their smallest ever recorded distribution.

• These declines are linked to regional impacts on coastal seagrasses from multiple above average wet seasons and severe storm events.

• Remaining seagrasses are highly vulnerable to further declines as they have been reduced to small remnant patches.

• The capacity for recovery of these seagrasses is poorly understood but could be slow for many meadows.

• Enhancements to the seagrass monitoring program have begun in order to assess seagrass recovery and establish local requirements and thresholds including: more frequent (quarterly) assessments of seagrass at key locations; examination of the status of seed banks and capacity for recovery; and establishing local drivers of seagrass change.

• Results of the enhanced monitoring program will be used to establish local drivers of seagrass change and inform what potential actions may be required to protect remaining seagrasses and facilitate recovery.

This report details results of the Cairns Harbour and Trinity Inlet annual seagrass monitoring program and the 2012 Cairns baseline survey conducted between October 2012 and January 2013. The Cairns seagrass monitoring program was developed in 2001 following a baseline assessment of the marine habitat within the port limits. Since 2001 seagrass at selected representative meadows has been monitored annually. An updated baseline survey of all seagrasses in the Cairns Harbour area was also conducted in 2012/13 as part of investigations for the Cairns Cruise Shipping Development Project EIS.

Results of the 2012-13 assessment found the smallest ever recorded area of seagrass with substantial declines occurring in previously robust and expansive meadows. This unprecedented loss has occurred over the past three years and left only small remnant patches of seagrass that are likely to be highly vulnerable to further natural and anthropogenic impacts. These declines were associated with multiple years of above average rainfall and severe storm and cyclone activity that have likely left seagrasses with a greatly reduced capacity for recovery and the potential for complete loss of meadows.

Similar large declines of coastal seagrasses have been recorded over the same period in other north Queensland monitored locations such as Mourilyan Harbour, Bowen and Townsville, pointing to regional climate related causes of declines. The cumulative impacts of multiple above average wet seasons combined with the 2010/11 La Niña events and Tropical Cyclone Yasi were unprecedented for the region and resulted in major declines of seagrass along the north Queensland coast and estuaries particularly in the wet and dry tropics regions.

In Cairns Harbour the large meadows lost were highly productive and key nursery grounds for commercial prawn species. Their near complete loss between 2010 and 2012 may have implications for local fisheries and ecosystem productivity, particularly if sustained for multiple years.

Seagrasses have the potential to recover, however this will be dependent upon the species present, the availability of propagules and a return to favorable growing conditions for seagrasses. Much of this information is not known for Cairns, especially the status and viability of seeds stored in the sediments (seed-bank) upon which the initiation of recovery is likely to depend. A range of enhancements have Cairns Seagrass Habitat Baseline Survey – 2012 TropWATER 13/17 recently been added to the seagrass monitoring program that will assist in answering these questions. These enhancements have been implemented in preparation for the Cairns Shipping Development Project and include:

• More frequent (quarterly) assessments of seagrass at key locations;

• Examination of the status of seed banks and capacity for seagrass recovery;

• Establishing local drivers of seagrass change;

• Assessments of light and temperature requirements for seagrass growth.

Results of these additional measures will be used to inform what actions may be required to protect the remaining seagrasses and facilitate recovery.

In addition, given the current poor state of local seagrasses, we recommend that the annual mapping and assessment program conducted every November continue in its expanded format in the lead up to the Cairns Shipping Development Project. In conjunction an assessment of adjoining areas such as Mission Bay and the coast between Ellie Point and Palm Cove would help identify any nearby source of seagrass propagules that could facilitate recolonisation of seagrasses in Cairns Harbour.

Item ID:	39697
Item Type:	Report (Report)
Keywords:	seagrass habitats, port management, recovery, resilience, dredging, marine monitoring, environmental monitoring
Additional Information:	Access: This report is openly accessible from the link to TropWATER's Technical Reports web page above. Copyright: Please refer to the copyright statement in the report.
Funders:	Far North Queensland Ports Corporation (FNQPC) trading as Ports North
Date Deposited:	25 Aug 2015 06:06
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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