Port of Karumba long-term seagrass monitoring: October 2012
Other Publication ResearchOnline@JCUAbstract
Seagrass meadows in the Port of Karumba were in a healthy and productive state in 2012. The meadow remained spatially extensive with the area of seagrass above the 19-year average and a record high density of Halodule uninervis seeds recorded. Although meadow biomass decreased by approximately 53% from 2011 and 2012, the density of the meadow remained well within previously recorded values. Seagrass biomass and distribution in the Karumba monitoring meadow has shown large seasonal and year to year variability during the 19 years of monitoring. This variability has been found to be influenced by climatic conditions such as river flow, temperature and long-term tidal exposure cycles (Rasheed and Unsworth, 2011). Low river flow in the preceding 12 months may explain much of the reduced biomass within the monitoring meadow in 2012, especially coupled with a reduction in critical periods of near tidal exposure reducing the availability of light to seagrasses. Halodule uninervis seeds and seed pieces in the Karumba meadow remained at high levels compared to previous years. In contrast no Halophila ovalis fruits were observed for a second consecutive year. Overall the occurrence of Halophila ovalis was at a record low in 2012. Karumba seagrasses remained in a relatively stable condition in 2012, and it is unlikely that anthropogenic activities had a significant impact on Karumba seagrasses in the twelve months prior to the 2012 survey. The survey also indicates that the meadow was in a robust condition and likely to be resilient to planned maintenance dredging activities in 2013. However, natural variation in climatic conditions has the capacity to reduce seagrass resilience in the future to the point where meadows may become vulnerable to activities that impact seagrass ecology. The Karumba seagrass monitoring program provides a guide to the resilience seagrass has to a range of potential impacts (e.g. land runoff or possible impacts from maintenance dredging of the port). Applying the best available knowledge through the ongoing monitoring program will ensure the ability to manage and mitigate potential threats to seagrass as they arise.
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13/15
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30
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TropWATER, James Cook University
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Cairns, QLD, Australia
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