Fremantle Port Inner Harbour and Channel ... - Fremantle Ports

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Due to the limited spatial area covered by the bathymetry surveys many of the permanentseagrass and sediment survey sites are not within the collected data area. As such, it is notpossible to ascertain changes in sediment redistribution for these sites. Some seagrassmonitoring sites (36TD, 36DT and 36H) which were within the data collection area showedpossible deposition of 0-0.02 m of materials during the time from December 2010 toDecember 2011. But, this amount of change is within the accuracy error of the bathymetricsurvey and thus is not reliable. As all sites are outside of the actual Offshore Disposal Area,the redistribution of sediments is expected to be minimal (
4. DiscussionWithin the Offshore Disposal Area, and surrounding zones of potential loss and effect fromthe IHD Project, 19.9 ha of seagrass loss was conservatively estimated to occur between preandpost-disposal habitat surveys. The majority of seagrass loss (76%) was within thebounds of the Offshore Disposal Area resulting from burial by disposed sediments. Seagrassloss in the surrounding area was likely due to plumes at the time of disposal and/or sedimentresuspension and redistribution of dredged materials causing indirect smothering and/or lightlimitation of seagrass.The selection of 15 permanent seagrass recovery monitoring sites within 'undisturbed','transitional' and 'disturbed' zones was validated with statistically significant differencesbetween zones in seagrass percentage cover and shoot density. Percentage cover ofP angustifolia ranged from 4-22% cover at disturbed sites, 17-27% at transition sites and 34-67% at undisturbed sites. The seabed was dominated by sand (30-87% cover) at disturbedand transition sites, while P. angustifolia dominated the coverage of the seabed atundisturbed sites. Wrack was also prominent at the transition site 11T and undisturbed site10H, and may be partially controlling the percentage cover of seagrass at these sites. Datafor undisturbed sites showed that mean shoot density (257-407 shoots per m 2 ) was withinthe range of natural seasonal variation recorded from the three sites monitored prior thissurvey (284-732 shoots per m 2 (Oceanica 2010a)). Seagrass density ranged from 12-407shoots per m 2 overall, which was within recorded variability for sites at this depth in thisarea. Seagrass density at disturbed sites ranged from 12-240 shoots per m 2 , at transitionsites ranged from 100-293 shoots per m 2 and undisturbed sites ranged from 257-407 shootsper m 2 . These statistically different values for both seagrass percentage cover and shootdensities represent a strong baseline data set to record potential future seagrass recoverywithin zones at these sites.Multivariate analysis of whole sediment nutrients and metals showed no combination ofchemical analytes was controlling the percentage cover or density of P. angustifolia.Sediment physicochemical data demonstrated no relevant differences in PSD, nutrients ormetals amongst zones which were considered to be able to affect seagrass health.Most (12 out of 15) permanent seagrass monitoring sites were not within bathymetry surveyarea. This was primarily due an expected lack of suitable seagrass sites within the OffshoreDisposal Area and the limited bathymetric survey area beyond the boundary of the OffshoreDisposal Area. Bathymetry data at the permanent seagrass monitoring sites which werewithin the survey area showed some sediment accumulation (0-0.02 m) during the pre- topost-disposal time frame (December 2010 to December 2011), but this level of accuracy iswithin the error of the bathymetric data and is not considered reliable. Although theavailable data does not allow for a quantitative analysis, it does highlight the possibility thatredistribution of sediments at disposal areas has the potential to affect seagrass recovery.Oceanica: Fremantle Ports: FP – Gage Roads Offshore Disposal Area Seagrass Recovery Project, Phase I – Initial Survey 33
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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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3. Annual Survey Footprint of Offsh
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Figure 3.2 Differences in bathymetr
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A one in five year storm event (as
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5. SummaryThere were zero non-compl
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6. ReferencesDEC (2009) Guidelines
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STATUS OF THIS DOCUMENTThis documen
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Report shall be 15 months from the
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6-3 If the Water Quality Monitoring
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Table 2: Summary of key proposal ch
Page 47: Fremantle Ports1 Cliff StreetFREMAN
Page 51: Fremantle Ports - Gage RoadsOffshor
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Page 58 and 59: Figure 1.1Figure 1.2Figure 1.3Figur
Page 61 and 62: Executive SummaryOceanica Consultin
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
Page 69 and 70: Figure 1.4 Benthic habitat within G
Page 71 and 72: 2. Methods2.1 Benthic habitat surve
Page 73 and 74: 2.2 Seagrass recovery2.2.1 Permanen
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
Page 83 and 84: Figure 3.2 Benthic habitat post dis
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
Page 93: Bathymetry data from December 2011
Page 97 and 98: 6. AcknowledgementsThis report was
Page 99: Appendix AGeo Oceans Report
Page 102 and 103: Benthic Habitat AssessmentTowed Vid
Page 104 and 105: 1. IntroductionGeo Oceans was commi
Page 106 and 107: Table 2 Tide predictions for the Po
Page 108 and 109: Figure 1 Substrate and biota habita
Page 110 and 111: Figure 2 Depth data collected durin
Page 112 and 113: Appendix 1: Video analysis biologic
Page 115: Appendix BGeoImage Report
Page 118 and 119: Table of ContentsIntroduction......
Page 120 and 121: Figure 1: Study site overview for s
Page 122 and 123: Project 1Project 1 aimed to generat
Page 124 and 125: Figure 2: Tier 1 classification res
Page 126 and 127: Limitations and assumptionsA number
Page 129: 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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