Smith, T.M., McKenna, S.M., York, P.H., and Rasheed, M.A. (2022) Green Island Jetty Repairs Seagrass Monitoring Final Report ‐ Sixteen Month Post‐Disturbance, October 2021. Report. TropWATER, James Cook University, Cairns, QLD, Australia.

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Abstract

As part of works for the Green Island Jetty repairs, utilization of an area for a contractors work barge was subject of agency approval for potential impacts to marine plants. As works progressed an area of seagrass was impacted by the barge sitting on the bottom and associated mooring blocks adjacent to the jetty during works. A monitoring program that incorporated pre‐disturbance baseline and reference areas of undisturbed seagrass was established to assess impacts and recovery of seagrasses in the impacted area. This report details results of the fourth and final post‐disturbance survey conducted 16 months after the works barge was removed. Key findings from this survey were:

1. In October 2021, sixteen months after removal of the works barge, seagrass within the barge footprint area had fully recovered.

2. Seagrass biomass within the barge footprint had returned to the same levels as the undisturbed reference areas and the pre‐disturbance baseline.

3. The area of seagrass impacted by the barge had largely recovered after 12 months and this recovery was sustained with no visible impact of the barge footprint 16 months following the disturbance.

4. Seagrass biomass was lower across all sites in October 2021 (disturbed and undisturbed reference areas) compared to May 2021 and November 2019 (pre‐barge impact), but biomass was similar to September 2020, with changes likely reflective of natural seagrass seasonality.

5. As seagrass had fully recovered with no signs of ongoing impact of the jetty works, no further monitoring of seagrass is required for the project.

Item ID:	79994
Item Type:	Report (Report)
Copyright Information:	© James Cook University, 2022.
Date Deposited:	24 Aug 2023 02:44
FoR Codes:	41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring @ 100%
SEO Codes:	18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180501 Assessment and management of benthic marine ecosystems @ 100%
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