WAMSI 2 - Kimberley Node - Project 1.3.1 - Reef Growth and Maintenance

Brief description

The goal of this project was to gain a regional understanding of the geomorphology of the Kimberley coral reefs, including their interaction with different substrates, morphological patterns, distribution and relative exposure to terrestrial and other impacts. The most cost effective way to determine reef growth architecture is through shallow seismic surveys which will provide information on foundations, previous reef growth events and Holocene buildup, also providing site survey data for collection of Holocene cores. The Holocene reef record will be obtained by coring selected sites, to gain an understanding of sea levels and growth history responses, timing of events during the Holocene, reef building communities, resilience and climate change responses. This involved addressing the following: In summary, our objectives were: - Use remote sensing with limited ground truth checking to establish the regional geomorphology, growth patterns and substrates of the inshore Kimberley reefs; - Determine the seismic architecture of selected Kimberley reefs as part of an assessment of Holocene reef growth and relation to antecedent foundations to assess reef growth; - Obtain a Holocene record of sea level change, reef building communities, chronology and growth patterns and climate history of selected inshore reefs for comparison with the short term record, where suitable coral material is obtained; - Where possible, quantify reef flat elevations, reef topography and morphology. Prior to commencement of acquisition of field data in 2013 time was invested in examining technical, equipment and logistic issues presented for SBP surveys and collection of coral reef cores for the remote and “tidally challenged” operational activities that will be required by this project. This is important also for site selection, which to some extent was dependent on other Kimberley project activities and priorities, and on ongoing discussions within WAMSI and with Industry groups. Ore pit mapping fieldwork was undertaken on a Holocene reef exposed in a mining pit on Cockatoo Island in July 2013 and a paper published on the findings in Marine Geology in 2015. In October 2013 SBP fieldwork was successfully completed and analysis of the data completed. Collection of cores was completed in October 2014, where possible, in the same locations as the SBP, all cores were been logged and sampled and samples sent for dating, dating results for all reefs, except Adele Reef, have been received. The ‘ReefKIM’ database has mapped more than 800 reefs and 30 analysed in detail. Data is stored at Pawsey Supercomputing Centre on 'WA Node Ocean Data Network' project under 'WAMSI2 > KMRP > 1.3 > 1.3.1'. There are seven main folders: 1) 000 Reports 2) 001 Metadata 3) 002 ReefKIM Database 4) 003 Reef Coring 5) 004 Cockatoo Island 6) 005 Seismic 7) 006 Papers. Detail of folders is available via '1.3.1_Folder_Structure.pdf' which is attached to this metadata record.

Lineage

Statement: *Coring* 2.1. Coring The survey equipment was assembled and tested at Curtin University and dispatched via truck to Cygnet Bay. Curtin personnel travelled to Cygnet Bay on the 30th of June 2014. Testing and mobilisation of the equipment (rotary and percussion coring equipment) onto the Atalanta IV and reef reconnaissance occurred on the 1st of July. 3 Field trips were undertaken from the 2nd to the 11th of July, 1st to the 10th of August and 16th to 22nd of October. All the operations were conducted on a tidal basis; therefore every day had a different range of working hours. The gear was demobilised on the 23rd of October and freighted to Curtin University premises. Curtin personnel returned to Perth on the 24th of October. Traditional Owner (Ranger) participation assisted the fieldwork. 2.1.1. Reef coring 53 cores were collected from 4 different islands, including the western and eastern reef of Tallon Island, northern and southern passage reef of Sunday Island, the inter-island reef of Bathurst-Irvine Island and Adele Island platform. The core site selection was undertaken to support interpretation of sub-bottom profiles from geophysical surveys, also located to ensure a spatially representative record of reef growth. Cores were obtained using percussion and rotary drilling core techniques. Percussion coring was carried out using both manual hammer and hydraulic post driver type LPD-THBP with normal pressure of 100 bar, the rotary drilling was carried out using hydraulic core barrels with a core diameter 80 mm and core length up to 1.5 m. 2.1.2. Core logging and sampling Cores were logged, sampled and photographed to record the following information: (i) the ratio of reef framework and matrix (following Embry and Klovan 1971); (ii) sediment textural characteristics (using the Udden-Wentworth nomenclature (Wentworth, 1922) as well as a visual assessment of sediment composition); and (iii) preliminary coral generic identification. Reef framework analysis and facies descriptions followed the terminology suggested by Montaggioni (2005), which highlights the growth forms of dominant coral reef builders and environmental indicators. 2.1.3. Ground Truth Contemporary reef communities and habitat were investigated on the reef flat during the coring survey. Visual assessment and description was the first stage to obtain information on modern reef communities and digital photos were then undertaken to aid the interpretation. Because of the difficulty of producing accurate species-level determinations, living coral community and core data were compared at the genus level. *Equipment* Percussion coring – aluminium pipe, hydraulic post driver, foot, clamp, slide hammer, hydraulic generator. Good for unconsolidated sediments, up to 6.2m of core (length of aluminium pipe) Rotary Drilling – Hydraulic Drill. Core Barrel. Produces a short section of core good for hard core, up to 1.5m

Statement: *Seismic* 1. Equipment and Software The main aim of this study is to gain a regional understanding of the geomorphology of the Kimberley coral reefs, including their interaction with different substrates, morphological patterns, distribution and relative exposure to terrestrial and other impacts. Shallow SBP surveys have been used to determine reef growth architecture and to provide information on foundations, previous reef growth events and Holocene build-up. Using the SBP data to establish coring targets, with the Holocene reef record from mine mapping to calibrate the stratigraphy, then coring selected sites in 2014, the study will gain an understanding of sea levels and growth history responses, timing of events during the late Holocene, reef building communities, resilience and climate change responses. Over 294 km of SBP records were collected from a representative suite of reefs including: - Sunday Island complex: southern fringing reef; Inter-island channel; NW exposed reef; - Tallon Island: exposed (western) and sheltered (eastern) fringing reefs; - Cockatoo Island: southern sheltered fringing reef; NW exposed fringing reef; - Irvine and Bathurst Islands: inter-island intertidal reef; south Irvine sheltered fringing reef; - Montgomery Reef: platform margin (3 locations); marginal platforms and associated reefs; margins of NW linear reef; - Molema Island; inter-island intertidal reefs; off-reef mud banks; - Adele Reef, Churchill, and Brue; inner shelf platform reefs. The reef sites were chosen to address as many of the reef growth questions posed in the original project proposal and recently reiterated in Wilson (2013). The KMRS and the southern Kimberley were targeted due to the availability of operationally suitable vessels and logistic backup necessary for the SBP work to be carried out efficiently and within budget. The large data base will continue to be evaluated further as information on reef growth and chronology becomes available in the sub-surface coring phase of the project, and it should be noted that details of some results provided here are subject to modification as further post-processing of data occurs and chronological control improves as the sub-surface data comes to hand. 2. Equipment The geophysical survey was undertaken using a Fugro DGPS positioning system and an Applied Acoustics boomer SBP system (Figure 2). A small pipe dredge was used to obtain surficial seabed samples. 3. Navigation and Positioning DGPS Receiver Fugro Seastar 8200XP/HP with Trimble Antenna interfaced to the acquisition software (SonarWiz 5, Chesapeake Technology Inc.). Real time data has been acquired using the WGS84 Datum (Latitude-Longitude, units Degrees). 4. Boomer Sub-bottom Profiler SBP Energy Source: Applied Acoustics CSP-P 300. SBP Sound Source: AA201 Boomer Plate, mounted on CAT100 surface tow catamaran. Receiver: streamer with 8 elements hydrophones. A/D Interface Box NI (National Instrument) Device Monitor V5.3.1. 5. Equipment Configuration The survey was undertaken using the vessel Atalanta IV, provided by Cygnet Bay Pearl Farm and Kimberley Marine Research Station (see Appendix 1 for vessel capabilities). Vessel Specifications Length: 10 m Beam: 2.85 m Draft: 0.30m Vessel survey speed: 2.5 – 3.5 Knots The boomer catamaran and the hydrophone array were towed away from propeller wash and turbulence (layback-25.55 m from the DGPS antenna). An extendable pole was used to adjust the offset between boomer and streamer, according to a triangulation as a function of the water depth. Foam pipes were used to improve the buoyancy of the streamer and protect the High Voltage cable connected to the boomer plate. After the sea trials, the best compromise for the output power level applied to the source was set at 150 Joule with a trigger rate of 333 ms throughout the survey. Sweep time was set accordingly with the water depth. Data were digitally recorded in Seg-Y format (Rev 1), using SonarWiz 5 as acquisition and post-processing software.

Statement: *ReefKIM* The Kimberley coastline is quite complex and covers a relatively large area. Therefore, it is not possible to visit every reef and map its coral communities in detail. It is prohibitively costly and time consuming. Thus remote sensing images are used as a feasible source of data, to detect and study coral reefs. Nevertheless, field surveys can be used in particular areas to verify the results of remote sensing images. Currently, remote sensing utilises powerful technologies, which increases the ability to detect reef geomorphology as well as to identify its habitats. Remote sensing images can be combined with other sources of data, such as geological maps and bathymetric charts, in the GIS environment. GIS has the ability to store data of different types and sources together, and to manage and process them to get appropriate results. Moreover, its mapping is accurate and credible, and can be updated. This knowledge enables estimation of likely types of coral communities, which can be tested against field data where it is available. This database will allow understanding of how the spatial distribution of reefs and, potentially, damage changes over time and pave the way for future studies of coral reefs in the region. 1. Map of Islands and Reef Distribution The locations of islands, reefs, shoaling areas and other related geomorphic features of the coast were extracted using heads-up digitizing from a combination of different data sources which include satellite imageries, aerial photography, geological maps and bathymetric charts of the Kimberley coast along with ground truth points. All images, maps and charts have been geo-referenced and projected according to the Australian standard (GDA 94) to ensure accuracy and consistency of the map. A range of features including coastline, islands, reefs, rock reefs, and areas of shoaling were precisely digitised to avoid any overlapping or mismatching between these features. The resulting features were stored in vector format. Information can be presented in different colours and symbols to facilitate discrimination between map features. Each feature is linked to its attributes such as the feature name, type, area, location, date of survey, source of data, map scale and any other related information which have been saved in an attribute table. The outputs from analysis of the data will facilitate understanding of linkages between geological substrate, reef geomorphology and reef classification and distribution. 2. Remote sensing images processing Image processing operations have been conducted on the satellite imagery using ENVI 4.3 software to enable image classification. Also ArcGIS 10 was used to manipulate various images with other data sources. Band threshold and segmenting image features have been applied to extract reef geomorphology and habitat and substrate classification of reef platforms form remote sensing images. Images from Landsat TM and ETM+ were initially used in this project to map reef geomorphic zones (Figure 5) and to classify habitat and substrate of reef platforms (Figure 5). All images were acquired at low tide and have very low cloud cover. After that radiometric and atmospheric corrections have been applied to these images to reduce image distortions. The targeted reef platform areas were subsetted to create an area of interest (AOI) for image processing. Both true colour and false colour composite images have been loaded to allow differentiation between image features and to enhance image classification. Unsupervised classification was undertaken on each image to derive a thematic map by statistically clustering pixels on the basis of spectral similarity. These clusters were combined and assigned to the thematic categories based on spectral signature, visual interpretation, expert knowledge and from ground truth. The classification scheme was designed to categorise habitats by both substrate type and the habitat cover. 3. Habitat and substrate classification of reefs in selected areas of Kimberley Region This phase of the project is ongoing, as more information about intra-reef geomorphological zones and the subsurface is required and as new imagery is sourced. Moreover, some data depends on the outputs of the other project activities. However, in the meantime, the available data from remote sensing imagery and bathymetric charts are being processed and analysed to obtain a preliminary geomorphological map of the reefs in selected areas on the Kimberley coast. The reef evolutionary classification scheme in this project will be based initially on the evolutionary classification model of Holocene shelf reefs proposed by (Hopley, 1982; Hopley et al, 2007). See figures 5 and 6 for analysis process. 4. Establishment of a Coral Reef geodatabase The development of a reef geodatabase for the Kimberley is useful as a research and management tool and is an important task which will continue as more information comes to hand. Initial input is from a wide range of sources such as reports, publications, atlases, books, maps etc. in different forms (hard and soft copies). The data are in the public domain, sourced through collaboration, or some has been purchased. The data has been compiled into a data library and information that is related to this project has been extracted and rectified and entered into a database. After digitizing and geo-referencing, selected information was represented as feature classes and raster-based datasets in a GIS as data layers using ArcGIS software, creating a geodatabase of the Kimberley coral reefs. This geodatabase contains the most significant elements and conditions that have direct or indirect influence on reef growth in the region, such as environmental, geological, geomorphological, biological, chemical, physical, oceanographic and climatic factors. These datasets can be updated and modified as new data becomes available, and presented as a dynamic map, figures and graphs associated with spatial information to facilitate more detailed analysis.