Long term seagrass monitoring in the Port of Mourilyan: November 2006
Other Publication ResearchOnline@JCUAbstract
This report details results from the November 2006 seagrass monitoring survey for the Port of Mourilyan conducted as part of the annual long term monitoring program as well as results from the post tropical Cyclone Larry survey conducted in May 2006. The monitoring program was developed following a baseline survey in December 1993 and examines selected representative seagrass meadows in Mourilyan Harbour. Total area of each monitoring meadow, species composition and seagrass density (above ground biomass) were measured for comparison with previous surveys. In 2006 seagrass meadows in Mourilyan Harbour remained in a fair condition despite the impacts of a severe category 5 cyclone in March. While declines had occurred for some meadows there had been evidence of recovery for most, with the densest intertidal meadow remaining largely unaffected and increases occurring for the major subtidal monitoring meadow. Despite this most intertidal meadows remained in a highly vulnerable state and were at their lowest area and biomass since the beginning of seagrass monitoring in 1993. The major drivers of seagrass change in Mourilyan Harbour appear to have been related to climate, flood and storm events. These events combined with the effects of local catchment use explain much of the seagrass change observed. The continued stress on these meadows and decline in meadow density left them in a far less resilient state in 2005 than had previously been the case. Many of these intertidal meadows suffered further major declines following tropical Cyclone Larry in March 2006, but most had begun to recover by November. While the recent changes to seagrass meadows at Mourilyan Harbour were most likely related to climatic conditions and the effects of cyclone Larry, human activities in the broader Moresby River catchment had the potential to exacerbate the effects of these natural events through agricultural and other disturbances resulting in high turbidity, nutrients, herbicides and acid sulphate runoff. The beginnings of post-cyclone recovery of seagrasses indicate that the marine environment in Mourilyan Harbour appeared to be relatively healthy although seagrass meadows still remained in a vulnerable state. We would expect the recovery of seagrass meadows to continue should regional conditions remain favourable for seagrass growth.
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PR07-2915
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0727-6273
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26
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Department of Primary Industries and Fisheries (DPI&F)
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Cairns, QLD, Australia
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