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Seagrass shoot countsPrior to disposal and as part of the baseline data collection for the IHD monitoring program,seagrass shoot count data were collected at locations 520 m north (SH50), 1200 m east(SH51) and 1600 m south (SH32) of the Offshore Disposal Area (Oceanica 2010a). Duringthe IHD program of sediment disposal, the seagrass shoot counts at these sites wererepeated as interim measurements on 17-25 March, 7-12 October and 3-12 November 2010(Oceanica 2010b). After the completion of sediment disposal on 30 October 2010, seagrassshoot counts were again measured during 7-15 December 2010 to determine if seagrasshealth was affected (Oceanica 2011a).Seagrass at the sites near the Offshore Disposal Area were reported as being P. sinuosaduring the IHD monitoring program, but samples have since been analysed and determinedto be P. angustifolia (M. Cambridge, personal communications). These two species are verysimilar (although P. sinsousa tends to be limited to shallower depths) and are difficult todistinguish in the field.Based on shoot counts during these periods, no adverse impacts to seagrass health weredetermined from dredging for any of these sites surrounding the Offshore Disposal Area.Seagrass shoot count means ranged from 284 shoot per m 2 (at site SH51 in January 2010) to732 shoot per m 2 (at site SH50 in December 2010) (Table 1.1). These data demonstrate thevariation in seagrass shoot counts within this area, both seasonally and between sites(Table 1.1).Table 1.1Seagrass shoot count data from monitoring sites established for the Inner Harbourand Channel Deepening ProjectSiteSH32Prior toDuring disposalPost disposaldisposalDec '09/Jan '10 March '10 October '10 November '10 December '10Mean (per m 2 ) 364 604 382 605 496Standard error 38.1 29.9 28.5 70.7 60.4n 14 14 14 14 14SH50*Mean (per m 2 ) 339 616 471 591 732Standard error 28.7 55.4 44.4 36.0 56.4n 14 14 14 14 14SH51Mean (per m 2 ) 284 471 500 602 630Standard error 13.0 24.8 59.1 51.2 42.4n 14 14 14 14 14Sites combined (SH32, SH50, SH51)Mean (per m 2 ) 329 564 451 599 620Standard error 28.3 40.6 45.0 51.4 56.5n 42 42 42 42 42Note:1. * SH50 is the combined data from SH50A and SH50B. This site was shifted during the IHD monitoring due to achange in Offshore Disposal Area boundary designation1.5 Current survey timingTowed video ground-truthing work was conducted by Oceanica Consulting Pty Ltd (Oceanica)and Geo Oceans Pty Ltd (Geo Oceans) on 11 and 12 October 2011. Permanent seagrassmonitoring sites surrounding the Offshore Disposal Area boundary were determined from theground-truthing data collected. Permanent site locations were located using towed videodata, in areas that were known to support seagrass prior to dredge material disposal,combined with spot dives by divers to determine overall site suitability. These sites weresetup on 14, 16 and 25 November 2011. Diver surveys to collect sediments, seagrass shootcounts and video footage were completed on 29 November, 12, 14 and 15 December 2011.These initial data were used to choose sites which were later refined for suitability using theinitial survey percentage cover and seagrass shoot count data.8 Oceanica: Fremantle Ports: FP – Gage Roads Offshore Disposal Area Seagrass Recovery Project, Phase I – Initial Survey
2. Methods2.1 Benthic habitat surveys2.1.1 Towed videoTowed video methods were used to accurately map the benthic habitat within the OffshoreDisposal Area, in areas immediately adjacent (within ~200 m of the Offshore Disposal Areaboundary) and areas south and southwest of the Offshore Disposal Area. Benthic habitatcoverage of the Offshore Disposal Area and surrounding areas was systematically surveyedby 102 targeted towed video ground-truthing transects (Figure 2.1).Remotely operated towed video system captured video footage that was geo-referencedusing GPS positioning locations. The video was analysed in real-time using Geo Ocean’s‘Geovideo’ software to classify the substrate and biota habitat characteristics while the videowas recorded. The quality assurance and quality control (QA/QC) process checked forerroneous data to ensure accuracy (Appendix A). Geo-referenced bathymetry data werecaptured throughout the field survey by a transponder attached to the survey vessel. Benthichabitat data were categorised according to substrate and biota as defined in Appendix A. Forthe purpose of this study and for the development of the benthic habitat map, habitatcategories were limited to: macroalgae, sand, wrack and seagrass.The benthic habitat ground-truthing data complements work already completed for the IHDmonitoring program and these data were combined to produce a benthic habitat map forGage Roads using a recent satellite image.2.1.2 Benthic habitat mapA remotely sensed image from the World View 2 (WV2) platform, with adequate waterpenetration, was located in the archives by GeoImage Pty Ltd. This true colour image has aspatial resolution of 2 m and was collected on the 25 December 2011.GeoImage Pty Ltd acquired this archived imagery and performed a geographic object-basedimage analysis in order to delineate benthic habitats and other substrate types in theimagery. Digital elevation, derived from a Light Detection and Ranging (LIDAR) and groundtruthingdata, derived from classified video tows, were used to enhance or aid in theclassification of the spectral information contained in the WV2 imagery (Appendix B).Oceanica: Fremantle Ports: FP – Gage Roads Offshore Disposal Area Seagrass Recovery Project, Phase I – Initial Survey 9
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Fremantle Port Inner Harbour and Ch
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Client: Fremantle PortsDocument his
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ContentsExecutive Summary .........
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Executive SummaryProject StatusFrem
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1. Introduction1.1 Background and p
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Figure 1.1Dredge areas, reclaimed a
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Table 2.2 Audit tableAuditCode801:M
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AuditCodeSubject Action How Evidenc
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Page 26 and 27: 5. SummaryThere were zero non-compl
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Page 37 and 38: 6-3 If the Water Quality Monitoring
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Page 63 and 64: 1. Introduction1.1 BackgroundThe Ga
Page 65 and 66: Figure 1.2Gage Roads habitat map in
Page 67 and 68: Figure 1.3Bathymetry for Gage Roads
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Page 75 and 76: Table 2.1Seagrass sites, zone desig
Page 77 and 78: Table 2.3Limits of Reporting (LOR)
Page 79 and 80: Sediment nutrients and metalsNutrie
Page 81 and 82: 3. Results3.1 Benthic habitat mapA
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Page 85 and 86: 3.2 Seagrass recovery3.2.1 Seagrass
Page 87 and 88: Table 3.4PERMANOVA table of results
Page 89 and 90: Table 3.7Data ranges and detection
Page 91 and 92: The bathymetry data for December 20
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Page 99: Appendix AGeo Oceans Report
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Page 104 and 105: 1. IntroductionGeo Oceans was commi
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Page 118 and 119: Table of ContentsIntroduction......
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Figure 1: Study site overview for s
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Project 1Project 1 aimed to generat
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Figure 2: Tier 1 classification res
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Limitations and assumptionsA number
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Appendix CSeagrass Monitoring Site
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Appendix ESeagrass Shoot Count Data
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Appendix GSediment Field Log
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Appendix INutrient and Metals Data
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MarineandFreshwaterResearchLaborato
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