Seagrass productivity, resilience to climate change and capacity for recovery in the Torres Strait: interim report 2011
Other Publication ResearchOnline@JCUAbstract
[Extract] The Fisheries Queensland Marine Ecology Group in collaboration with the Torres Strait Regional Authority (TSRA) Land and Sea Management Unit established a program to develop critical information for the management of dugong and turtle in the Torres Strait by understanding how their key food resource, seagrass, is affected by seasonal change, climate and their ability to recover from impacts. The project will also provide key information on how seagrasses in the Torres Strait may be affected by climate change and how this may impact on turtle and dugong management. This study is aimed at developing an understanding of the potential impacts to seagrass from climate change and other anthropogenic impacts such as shipping accidents and the subsequent implications for the management of dugong, turtle and other fisheries that rely on seagrasses in the Torres Strait. Several experimental sites were set up on intertidal and subtidal seagrass meadows examining seagrass recovery, productivity and potential environmental and climate drivers of change including light, temperature, salinity and pH. Initial results show the role of sexual and asexual reproduction (seeds versus runners) was a major factor in determining the recovery of cleared experimental plots. In general, preventing asexual colonisation had a significant impact on the rate at which seagrass recovered in both the intertidal and subtidal zones. Five months after clearing, no plots had recovered to undisturbed levels when only sexual colonisation was allowed in either the intertidal or subtidal zones. In contrast, where asexual colonisation was permitted seagrass biomass had recovered to the level of undisturbed controls at intertidal sites and was significantly higher than treatments where borders prevented asexual colonisation at subtidal sites. Some seagrass species in both the intertidal and subtidal had significant seed banks whilst others did not despite their capacity to produce long-lived seeds. Daytime low tide exposure events for intertidal seagrass typically occurred over two periods each month. During these exposure events the shallow pools of water that were retained over the seagrass meadow became super heated, with the maximum water temperature recorded being 40.5°C in late March 2011. Light data collected in the intertidal and subtidal regions demonstrated the high variability exhibited in the amount of light that reaches seagrasses and is available for use in photosynthesis. Average PAR levels were approximately three times higher in the intertidal than in the subtidal. PAR levels showed expected responses to weather and tidal patterns. A more detailed report on the first year of the study will be completed by mid 2012 and will better be able to establish links between climate variables and seagrass condition as more data becomes available. This report will also encompass productivity and growth rates of Torres Strait seagrasses as well as further environmental parameters associated with climate change.
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23
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Department of Employment, Economic Development and Innovation (DEEDI)
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Cairns, QLD, Australia
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