Benthic sediment surveys of inner Darwin Harbour and shallow water areas in and around Bynoe Harbour (2017): GA0358 and GA0359 – Post-survey report

Benthic sediment sampling surveys in inner Darwin Harbour (GA0358) and shallow water areas in and around Bynoe Harbour (GA059) were undertaken in the period from 29 May to 16 August 2017. Partners involved in the surveys included Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and the Department of Environment and Natural Resources within the Northern Territory Government (NT DENR) (formerly the Department of Land and Resource Management (DLRM)). These surveys forms part of a four year (2014-2018) science program aimed at improving knowledge about the marine environments in the regions around Darwin and Bynoe harbour’s through the collection and collation of baseline data that will enable the creation of thematic habitat maps to underpin marine resource management decisions. This project is being led by the Northern Territory Government and is funded by the INPEX-led Ichthys LNG Project, in collaboration with - and co-investment from GA and AIMS. The program builds upon an NT Government project (2010-2011) which saw the collection of baseline data (multibeam echosounder data, sediment samples and video transects) from inner Darwin Harbour (Siwabessy et al. 2015). Here we present an account of the field methods and data summaries (location maps and comprehensive metadata) for the collection of 285 seabed sediment samples designated for grain size and inorganic elemental analyses, and organic matter concentration, source and reactivity measures. Metadata is also provided for seagrass and hardground observations. The seagrass observation data have been incorporated into DENR’s seagrass database. The baseline environmental datasets acquired during these surveys will be merged with like datasets from three other surveys conducted (i.e. GA0351/SOL6187, GA4452/SOL6432 and GA0356) as part of the overall project to create a set of interpolated maps of abiotic parameters with full coverage for the region. Some of the maps will be integrated into final habitat mapping products. Baseline data from the surveys will also be made publically available via the Geoscience Australia website ( http://www.ga.gov.au/ ).