Abbot Point proposed dredge disposal areas: benthic habitat survey: 2013
Other Publication ResearchOnline@JCUAbstract
This report details the results of a survey conducted on benthic habitats, macro invertebrates and sediment composition in the revised proposed dredge material disposal area at Abbot Point. Two potential sites were identified in this area for consideration for spoil disposal (site 1 & 2). The survey was commissioned in preparation for the planned TO/T2/T3 capital dredging project and as a response to the Public Environment Report (PER) to investigate alternative spoil disposal locations to those initially identified in the draft PER. Through the PER process, a range of constraints on site selection were identified including presence and density classes of seagrass, macro algae and benthic communities. This survey mapped and examined these habitats to assist in appropriate dredge disposal site selection. In general the seagrass, macro invertebrate and algae communities, as well as the sediment composition within the survey area of this study were typical of communities found in the Great Barrier Reef 'middle shelf' and found at Abbot Point in previous baseline surveys. Key findings of the survey include: • The dominant habitat feature within the survey area was mostly open substrate with a low to medium density of benthic community life. There were no benthic communities that were classified as 'high density'. • Seagrass was present at 25% of the survey sites and was found in and surrounding disposal site 1. • Seagrass habitat was characterised as having a low density of cover and low diversity. • Seagrass distribution mapped in this survey is likely to represent the seasonal maximum of seagrass abundance for the Abbot Point area. • Mud scallops occurred in low densities at 45% of the survey sites. • Macro algal communities occurred in aggregated patches within the survey area. Two out of the three regions where algae was identified had less than 20% cover. • The particle size distribution of the proposed spoil disposal sites in this survey comprised predominantly fine gravel, medium sand and fine silt with a minor clay component. Of the 2 disposal sites, site 2 in the south-east of the investigation area, contained the lowest density of benthic habitats and algae and did not have any seagrass present. Predicted plume extent from this site also had a smaller interaction with moderate density algae, benthic macro invertebrates and seagrass compared with site 1. Many of the benthic communities described in this report are likely to vary seasonally and between years and there is potential for changes to distribution and density recorded in this report.
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13/39
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TropWATER, James Cook University
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Cairns, QLD, Australia
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