Wireless Sensor Networks

Summary

Sensor-Float at Heron Island.

Wireless Sensor Networks are a leading edge technology that provides real time spatially dense measurements of bio-physical environmental variables. In the marine environment they have particular application to the study of benthic ecosystems. The term 'sensor network' refers to an array of small, wirelessly interconnected sensors that collectively stream data to a central data aggregation point. Some sensors can be set to sample according to prevailing conditions (e.g. monitoring salinity more frequently after rainfall), but since communications with the sensors is bi-directional they can also be manipulated by central land-based control systems as part of an 'smart' response to real time events.

Wireless Sensor Networks have been deployed in the Great Barrier Reef (GBR) to collect data related to the interaction of heat and light on coral bleaching and to understanding the impact of upwelling from the Coral Sea upon the productivity of Great Barrier Reef ecosystems. They allow an understanding of how ocean processes impact reefs as well as providing detailed environmental information down to the coral bommie level. They give critical environmental data that provide context for other studies such as the timing of coral spawning and environmental triggers for fish behaviour.

While sensor networks are a leading edge technology to ensure the data is integrated into the IMOS set of observations oceanographic grade instruments have been utilised so that the observations have the same level of quality as for the deep water deployments. This melding of new and established technologies ensures that the data is fit for purpose for a range of scientific questions.

The immediate value of the network is its ability to return spatially dense bio-physical measurements in real-time. Real time data allows for events of interest to be detected and acted upon as they occur. The data can also be linked to modelling systems to give short term forecasts of future conditions. As such Wireless Sensor Networks offer a unique coastal monitoring capability and are suitable for a range of coastal or shallow water monitoring applications.

Instrumentation and Data

Wireless Sensor Networks located on the Great Barrier Reef (GBR) collect real-time data at spatial and temporal scales required to understand complex marine processes, particularly those involving the interface between pelagic and benthic environments. Data from the local network is aggregated and streamed in real-time. This includes traditional oceanographic variables such as temperature and salinity but also video, imagery and above water parameters such as meteorological observations.

Wireless Sensor Networks were initially deployed at seven sites along the Great Barrier Reef, from Heron Island in the south to Lizard Island in the north. In 2014 there was a consolidation of sites, currently there are five sites in operation across the Great Barrier Reef. The IMOS work has been extended via other projects with an additional three sites being established in the Torres Straits; while these sites are not IMOS funded the data goes into the IMOS Oceans Portal.

All of the deployments were completed by 2010 although a number of Tropical Cyclones (Hamish, 2009, Yasi 2011, Ita 2014 and Nathan 2015) caused damage to some sites and while the damage has been repaired there are some data gaps as a result. The upside is that the sites have recorded detailed observations from each of the cyclones giving new insights to the impacts of these systems.

Four of the sites have been installed as part of the Tropical Marine Network of Island Research Stations with specialised access to data and the network available from these stations. These include the Heron Island Research Station (HIRS) on Heron Island operated by the University of Queensland, the One Tree Island Research Station (OTIRS) operated by Sydney University, the Orpheus Island Research Station (OIRS) operated by James Cook University and the Lizard Island Research Station (LIRS) operated by the Australian Museum. At each of the Stations a dedicated touch screen data display has been installed to facilitate local access to the real time data, the full set of data can be found on the Australian Ocean Data Network (AODN) Portal.

Graph showing daily water temperatures (red line) for Davies Reef against the long term mean (dashed green line), historical upper and lower limits (purple and blue lines) and the known bleaching limits (dashed black line). The data shows that for summer 2014-15 Davies Reef came very close to the known coral bleaching threshold.

Application of Data

  • Temperature data from the 2014-15 summer has been analysed against previously developed empirical coral bleaching thresholds. The data shows that a number of reefs experienced short term (days) temperatures higher than their long term means with some close to the bleaching thresholds. If general ocean conditions move into an El-Nino pattern then we can expect from previous events to get periods of high summer conditions meaning that the risk of coral bleaching may rise in the next few years. To read more click here.
  • The Lizard Island site experienced its second Tropical Cyclone (T.C. Nathan) in less than a year with T.C. Ita going over the station in April 2014 and T.C. Nathan in April 2015. The IMOS equipment recorded the most intense wind gusts of any cyclone to date at over 180 kilometres per hour. While the cyclone was quick to pass over the station it came from a different direction to Ita a year before meaning that coral areas that had survived one cyclone were exposed to the second. As a result the coral has been degraded in parts around the island and it will be interesting to monitor the recovery of this reef over time. To read more click here.
  • A novel over-the-horizon microwave communications system has been in operation between the Australian Institute of Marine Science (AIMS) and the Davies Reef station located some 77 kilometres off-shore. The link uses a humidity duct or layer of humid air that sits above the water surface in the tropics to trap and guide the microwave signal over distances greater than line of sight. The link is to be extended from the Davies station out further to the Myrmidon Reef station in May 2015, initially in test mode but going into operational mode if successful.
  • An underwater video camera has recently been installed at Heron Island which transmits real time high definition video from an underwater bommie back to the island research station. The camera can be programmed to pan around to set points allowing for long term monitoring of corals, experiments and water quality as well as providing a real time view of the reef.

Useful Links

The Wireless Sensor Networks Facility Publication Report - If you have any questions regarding the data, or corrections, or would like to add a publication or presentation that uses IMOS data please contact the IMOS office via email: publication(at)emii.org.au.

Contact:

Scott Bainbridge

Partners:

The wireless sensor networks are supported by the Island Research Stations under the Tropical Marine Network (TMN) banner. Partners include the University of Queensland which run the Heron Island Research Station, the University of Sydney which run the One Tree Island Research Station, James Cook University which run the Orpheus Island Research Station and the Australian Museum that run the Lizard Island Research Station.

The Facility had significant initial funding from the Queensland State Government via the Department of Science, Information Technology and Innovation.

The Facility also was a partner in the ARC Intelligent Sensors, Sensor Networks and Information Processing (ISSNIP) project.

International Programs:

The Facility is a founding member of the Coral Reef Ecological Observation Network (CREON) and is a participant in the Ocean Data Interoperability Platform project (ODIP).

 

Your access to the IMOS Wireless Sensor Network data discovery and exploration is through the Australian Ocean Data Network (AODN) Portal.