Long term seagrass monitoring in Cairns Harbour and Trinity Inlet: November 2007

Rasheed, M.A., McKenna, S.A., Sankey, T.L., and Taylor, H.A. (2008) Long term seagrass monitoring in Cairns Harbour and Trinity Inlet: November 2007. Report. Department of Primary Industries and Fisheries (DPI&F), Cairns, QLD, Australia.

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Abstract

This report details results from the November 2007 seagrass monitoring survey for Cairns Harbour and Trinity Inlet conducted as part of an annual long term monitoring program. The monitoring program was established following a baseline survey in December 2001 and examines selected representative seagrass meadows in Cairns Harbour and Trinity Inlet. Total area of each monitoring meadow, species composition and seagrass density (above ground biomass) were measured for comparison with previous surveys. Results of the program are used to assess potential impacts of port activity on seagrass meadows and as an overall indicator of marine environmental health of the port. In 2007 seagrasses in Cairns were generally healthy with:

• Total area of seagrass meadows the highest since monitoring began in 2001.

• The continued expansion of a high density meadow that began forming in 2005.

• Recovery of subtidal meadows in Trinity Inlet reversing recent declining trends.

While several key indicators pointed to overall good health of seagrasses there were differences between meadows. The large meadows located on the banks adjacent to Cairns Harbour have had three consecutive years of biomass decline despite significant gains in area. These changes however appeared to be consistent with the prevailing climate conditions in the area and for other similar seagrass areas monitored in north Queensland. The results of seagrass monitoring indicate that current port activities such as dredging and shipping movements through the channel had not resulted in substantial impacts on seagrasses. However other events have the potential to increase the vulnerability of seagrasses to such impacts in the future. The area is facing a range of impacts from both natural causes and the cumulative effects of urban, industrial and port developments. Recent events such as substantial wet season runoff and sediment inputs from developments in the harbour had the potential to reduce the natural resilience of seagrasses in the region. The increased abundance of seagrass in Cairns Harbour may have flow on effects for fisheries in the area especially tiger and endeavour prawns which utilise these areas as a nursery ground. There was also an increase in seagrass species that are preferred as a food source by dugong and green turtles. The results suggest that the marine environment in the port was in a good condition. In Cairns seagrasses are located in proximity to major infrastructure, dredged channels and urban and industrial discharges and are thus ideally placed as an indicator of marine environmental health.

Item ID: 39888
Item Type: Report (Report)
Keywords: seagrass habitats, port management, recovery, resilience, dredging, marine monitoring, environmental monitoring
ISSN: 0727-6273
Funders: Cairns Port Authority (CPA), Qld Department of Primary Industries and Fisheries (DPI&F)
Projects and Grants: DPI&F Marine Ecology Group (MEG)
Date Deposited: 25 Aug 2015 05:45
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050205 Environmental Management @ 50%
05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050206 Environmental Monitoring @ 50%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960503 Ecosystem Assessment and Management of Coastal and Estuarine Environments @ 50%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 50%
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