Port of Hay Point seagrass, algae and benthic macro-invertebrate community survey: July 2004

Rasheed, M.A., Thomas, R., and McKenna, S.A. (2004) Port of Hay Point seagrass, algae and benthic macro-invertebrate community survey: July 2004. Report. Department of Primary Industries and Fisheries (DPI&F), Cairns, QLD, Australia.

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This report details the results of a survey of seagrass, algae and benthic macro-invertebrate communities in the Port of Hay Point (south of Mackay) that was conducted in July 2004. The survey was commissioned by the Ports Corporation of Queensland (PCQ) as a joint project with the Department of Primary Industries and Fisheries (DPI&F) and the CRC Reef Research Centre to aid in planning for future port expansion that would have minimal impacts on sensitive fisheries and benthic habitats. PCQ is currently investigating the possibility of establishing a departure path and expanding the berth pocket and apron areas of the port to allow better shipping access.

A range of survey techniques were used to describe the benthic communities that occurred in the port and included a real time camera system and sled with mini-trawl net towed behind a research vessel. The techniques employed integrated a large area of seafloor at each site and were ideal for describing patchily distributed life that typifies the deep-water areas forming the majority of the Hay Point port limits.

The Port of Hay Point contained a diverse range of benthic community types. Benthic macroinvertebrates were found throughout the port with algae and seagrass communities also occurring in the majority of the survey area (56% and 80% respectively). While a diversity of taxa and community types were found, the dominant feature of the benthic habitat was open substrate containing a low percent cover of benthic life. There were no benthic communities that could be described as "high density" with the majority of regions having less than 5% cover. Smaller medium density regions did occur however, with some areas of seagrass, algae and benthic macro-invertebrates containing greater than 20% cover.

The benthic macro invertebrate and algae communities were typical of other deepwater (>10m) regions between the mainland and the Great Barrier Reef. These communities were generally dominated by open space with only a low percent cover of life.

The large area of seagrass found and mapped within the port was more unexpected, especially in July, which is usually considered the "low season" for deep-water seagrass distribution and abundance. The seagrass species found were likely to be highly variable both seasonally and from year to year. Atypical climate conditions in central Queensland have possibly created ideal conditions for the growth of these deeper water seagrass meadows.

The seagrass meadows were of a type preferred as food for dugong and may provide a seasonally important food source for dugongs moving along the coast between the Dugong Protection Areas (DPA's) to the north and south of the port.

The habitats mapped in this survey were likely to have some fisheries values although the importance of these low percent cover communities in deep water areas is poorly quantified. The value of these seagrasses as a habitat for juvenile prawns and commercial fish species was likely to be lower than denser meadows occurring in intertidal areas but their rapid growth and high turnover may be seasonally important to the overall productivity of the area.

The departure path proposed for the port appears to be in a sensible location from a biological perspective, generally passing through open substrate or low-density communities. The proposed locations for dredge spoil disposal, however, contained sections of medium density seagrass, algae and macro-invertebrate communities. These communities also occurred in the existing spoil ground indicating they had a capacity to cope with some level of disturbance associated with dredge spoil disposal. The feasibility of modifying the location of the spoil ground to avoid these higher density areas should be considered given the significantly larger volume of material to be disposed of from the planned developments.

This was the first time that benthic communities have been examined at this scale in Hay Point so direct historical or seasonal comparisons were not possible. The survey provides a good indication of the location of significant benthic communities in the port but it is likely that many of the communities described would be variable seasonally and between years. The extent, species composition, and density of seagrass communities for example, may be greater in spring-summer, the typical "high season" for seagrass growth. Further investigations conducted during this time of year would be required to ascertain if this was the case. This survey provides a baseline from which future comparisons could be made.

Item ID: 39706
Item Type: Report (Report)
ISSN: 0727-6273
Keywords: seagrass habitats, port management, recovery, resilience, dredging, marine monitoring, environmental monitoring
Funders: Ports Corporation of Queensland (PCQ), Qld Department of Primary Industries and Fisheries (DPI&F), CRC Reef Research Centre
Projects and Grants: DPI&F Marine Ecology Group (MEG)
Date Deposited: 25 Aug 2015 05:38
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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