Long-term seagrass monitoring in the Port of Thursday Island: February 2012
Other Publication ResearchOnline@JCUAbstract
Seagrass habitats are valuable fisheries resources that show measurable responses to changes in water quality. These attributes make seagrasses an ideal metric to determine the health of estuarine and coastal environments. A network of long-term seagrass monitoring sites has been established at various port locations throughout Queensland by Fisheries Queensland to assess the condition of marine habitats. Outcomes of these programs assist in the planning and development of port operations, helping to achieve minimal environmental impact. Furthermore, these programs assist fisheries management to achieve protection of key fish habitats. This report details the findings from the fifth biennial Port of Thursday Island long-term seagrass monitoring program conducted in February 2012. The 2002 baseline survey identified some of the best examples of intertidal and subtidal seagrasses in Queensland and provided a good foundation from which the biennial monitoring surveys in the Port of Thursday Island could be based. Nine seagrass meadows representative of the range of seagrass communities present and located in areas potentially influenced by port operations and developments were selected for long-term monitoring from the baseline survey. The results of the February 2012 monitoring survey found that seagrasses were in a relatively healthy and productive condition. Seagrass above-ground biomass for the majority of monitoring meadows was the highest recorded since peak levels seen in 2004. Increases in meadow biomass from 2010 to 2012 ranged from 15% to 199%, with two thirds of the meadows increasing in biomass by over 100%. The area of the monitoring meadows has generally remained stable throughout the course of the monitoring program with modest increases or decreases in meadow distribution. Seagrasses in the Port of Thursday Island are influenced by a complex interaction of a number of different climatic factors including rainfall, wind, solar irradiance, temperature, daytime tidal exposure and photosynthetically active radiation (PAR), which are known to affect seagrass growth, recruitment and mortality. It is likely that a combination of these factors has led to the observed changes to seagrass meadows in the Port of Thursday Island rather than any changes in port or anthropogenic activities. This fifth biennial survey has helped establish a clearer picture of the natural inter-annual variations and the relationship between seagrass change and climate. However, correctly interpreting the causes of seagrass change is difficult when surveys are undertaken biennially. An annual seagrass program similar to other port locations throughout Queensland would provide a greater understanding of seagrass health and dynamics. The existing biennial program suggests the port's marine environment is relatively healthy with seagrasses in good condition. The range of natural seagrass changes measured to date will enable any future changes to be placed in a clearer perspective.
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37
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Department of Agriculture, Fisheries and Forestry (DAFF)
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Cairns, QLD, Australia
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