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As part of the NEAR-Lab's Conservation Technology Initiative (CTI), Dr. Helen H. Ou and Eric Sorensen conducted acoustic sensing experiments at multiple sites in Hawaii in March 2010. The three-week long experiment consisted of five sea trips. Ou and Sorensen tested the performance of latest SOREN 3.0 sensors for the detection and localization of motorized vessels in the Marine Protected Areas (MPA) of Hawaii. During the three-week experiment, the NEAR-Lab received on site assistance from The Nature Conservancy in Hawaii, the Division of Aquatic Resources of the State of Hawaii, and the University of Hawaii at Manoa.
CTI is a five-year project started in 2008. It is a joint effort between Portland State University (PSU) and The Nature Conservancy (TNC). CTI is led by Principal Investigator Dr. Lisa Zurk, Co-Principal Investigators Dr. Martin Siderius and Dr. James McNames all professors of electrical and computer engineering at the Maseeh College of Engineering and Computer Science at PSU and Dr. Mark Systma professor of environmental science at PSU, and TNC partner Jean-Louis Ecochard the vice president and chief information officer of TNC. CTI seeks cutting-edge technology for conservation application with the goal of establishing a link between research institutions and conservation organizations. During an earlier phase of CTI, the NEAR-Lab has developed a SONAR imaging tool to monitor underwater habitats that are affected by pollutions and human activity. It has been applied to visualize endangered coral reef surfaces in the Hol-Chan Marine Reserve of Belize.
On the Hawaiian Islands, the NEAR-Lab collaborated with TNC to explore sensing technologies to monitor the Marine Protected Areas (MPA). Ou met with the Pupukea Community Group to discuss the best match of interests between CTI and the local community. Project objectives included providing a surveillance network to monitor intrusion/poaching activities in the MPAs and to enhance the protection of endangered marine species inhabiting the MPAs. They conducted field measurements in the MPAs, especially in Pupukea (Honolulu) and Ahihi-Kinua (Maui) where illegal vessel access is of great concern to the state.
To date, the hydrophones developed by the NEAR-Lab are well-suited equipment for recording underwater noise. Data collected using these hydrophones is analyzed by advanced SONAR signal processing techniques to identify the noise source in a marine environment. The NEAR-Lab has conducted extensive research in detecting self-emitting sources especially movement of boats, using passive acoustic data. NEAR-Lab researchers have demonstrated a relationship between the harmonic pattern and the vessel signatures such as engine noise and propeller movement. This data helps identify specific boats.
In total four sensors were deployed, including the hydrophones, embedded microprocessors and batteries tightly sealed in aluminum packages. These sensors were entirely passive and did not create any negative environmental impact. They were attached to subsurface floats and lowered into the ocean, approximately 50-100 ft beneath the surface. To protect underwater environment in the MPAs the NEAR-Lab used bags of sand as anchors. The sandbags were made of dissolvable material. After data collection, the entire system except for the sandbags was retrieved.
The project was not without setbacks. Researchers faced harsh weather including five to eight foot swells and 10 to 15 mph winds. After analyzing the data collected in the first deployment trip, they realized a negative impact of high-energy snapping shrimp noise in tropical waters. In the following experiments, they had to deploy the sensors at deeper locations (more than 170ft) to avoid such noise. While data analysis remains an on-going effort in the lab, the initial processing tools had successfully detected a few motorized vessels near the Ahihi-Kinau MPA boundary during night time.
