Port of Abbot Point long-term seagrass monitoring: annual report 2011-2012
Other Publication ResearchOnline@JCUAbstract
This report summarises the results of the coastal and deep water seagrass monitoring program conducted between September 2011 and September 2012 at the Port of Abbot Point. The seagrass monitoring program at Abbot Point was developed in 2008 following two baseline assessments of the marine habitat within the port limits. Since 2008, seagrass at selected representative sites has been monitored quarterly. Significant losses of density and distribution of seagrasses at Abbot Point were observed after the La Niña events of 2010/11 and severe Tropical Cyclone Yasi, the most likely factors that caused these losses. There is evidence of recovery of seagrass at some of the deep water monitoring sites, however, the coastal inshore meadows had not had any significant recovery by September 2012. Coastal habitats along the Queensland coast are regularly exposed to flooding & cyclones, but the scale and longevity of the 2010/11 La Niña events were unprecedented and may have left seagrasses at Abbot Point, particularly the inshore species, with substantially reduced resilience and capacity for recovery. Similar declines to coastal seagrass meadows have been recorded throughout the wet and dry tropics regions where seagrasses are monitored. Seagrasses at Abbot Point have the potential to recover, however, this recovery is dependent upon the species present and the availability of seed reserves. Halophila, the dominant seagrass genera in the offshore meadows, has a high capacity for recovery through the use of seed reserves in the sediment. In contrast, the shallow near-shore species Halodule uninervis failed to recover quickly from experimental disturbance and relied on asexual propagation, making them more vulnerable to widespread loss. The same results have been reported for Zostera capricorni, another in-shore species at Abbot Point that has not recovered from natural events. Seed-bank assessments of Halodule uninervis and Zostera capricorni at Abbot Point indicate that the potential for these species to recover at Abbot Point may be restricted, as only a small bank of Halodule uninervis seeds and no Zostera capricorni seeds were found in the sediment at the monitoring meadows. The declines in Abbot Point seagrasses over recent years mean that they likely have a reduced resilience to further impacts and stressors. The cumulative impacts of natural stressors combined with future developments associated with port expansions have the potential to impact seagrasses. Modeling indicates that turbidity associated with these planned developments is not likely to reach the coastal meadows that have been most effected, with any interactions occurring in the deeper offshore seagrasses closer to proposed expansions. Several initiatives have been included in the monitoring program to ensure relevant information is available to manage these seagrasses and ensure impacts from future port activity on seagrasses are minimised. These include an examination of the light requirements and capacity for recovery of the key offshore species so that appropriate management thresholds are developed to maintain the ability of seagrasses to grow and continue to recover.
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13/02
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43
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TropWATER, James Cook University
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Cairns, QLD, Australia
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