A Breath of Fresh Air: USVs Map Hypoxia in the Gulf
The scientific method serves as a standard for research, guiding analytical and investigative projects. Though taught to generations of students, its steps are far from ancient, as technological advancements help researchers to develop and modernize each of its steps, saving time, money and even lives. Data collection, the middle step of the scientific method, is no exception. Many projects require robust datasets, often collected from extreme environments or over lengthy periods of time. The University of Southern Mississippi (USM), with the help of SeaTrac Systems, has turned to autonomous solutions while conducting hypoxia research in the Gulf of Mexico.The partnership, which includes the National Oceanic and Atmospheric Administration (NOAA), maps potential hypoxia in the Gulf and how it impacts local fisheries and fish populations. Hypoxic zones, also known as dead zones, are areas of water in which oxygen levels are decreased due to nutrient pollution, often significantly impacting aquatic life. The collaboration recently completed a successful phase two of the project, building on an earlier phase and moving beyond proof-of-concept to deploy multiple SP-48 uncrewed surface vehicles (USVs). "It's a very labor-intensive, crude operation with a large research vessel," said James Thompson at USM. "We approached that from an uncrewed vehicle standpoint; we can modernize that with the tools that are available now."The Pickup Truck of USVsThe star of this research is the SP-48 USV, which stands for "solar powered" and "4.8 meters." At roughly 15 feet long and about 650 pounds, it can run 24/7 for months at a time thanks to a large array of solar panels on the deck that charge an internal battery. It is designed to run both near- and off-shore; within the scope of this project, the USV could be as near as five miles or as far as 40 miles. "The boat itself is really a platform for data collection," said Hobie Boeschenstein, director of operations and business development at SeaTrac. "We think of it as a pickup truck, where the platform itself isn't all that useful for anyone. It's really all about the payloads you can put on it and being able to quickly swap those out and put on different items—either sonar units or water quality sensors or oceanographic sensors."The SeaTrac SP-48 USV. Credit: USM/SeaTrac SystemsAcross the phases of the project, SeaTrac and USM saw changes to the USV to make it more versatile and robust in its data collection abilities. "Specifically for this one," Boeschenstein added, "the big development effort on our side was the winch and being able to support profiling down to the seafloor. Throughout the course of the project, layering on additional communications like the Starlink Mini was a big addition from when we first started.""It's so versatile as far as what we can put on it. We tested cameras, we tested some collision avoidance tech—a lot of different things while we ran this hypoxia mission. That just goes to show you how flexible this boat is," Thompson confirmed. "One of the other things that we collected, just because we could, was acoustic current data. It really is a pickup truck. You can put so many things onboard and with the size of the battery and the ability to generate so much solar power, it's a game changer."Phase OnePhase one of the project served primarily as proof-of-concept, testing the vehicles and various sensors and their ability to collect the necessary data. "We learned a lot of what we needed to tweak to make that function," Thompson said. "And we did it, and much better than we expected."The logical progression was testing longer duration surveys, assessing different sensors setups and running multiple USVs at once in different configurations. "What we learned," Thompson added, "was that the vehicle could produce all this power, but we weren't taking full advantage of that." They switched the sensors to be powered or recharged by the USV, which made a significant difference in terms of how much data they could collect. "We didn't have to limit ourselves based on the power available in the sensors. We could collect more and more data. And it showed the advantage of being able to not just hit the certain coordinates that we'll hit every year, but also find where that boundary of hypoxia changes, zero in on that by taking additional data samples."SeaTrac was heavily involved at the start of this project, developing new features like a winch to take sensors from the surface to the seafloor. "A very important part of the hypoxia mapping is getting all the way to within a meter of the seafloor," said Boeschenstein. "Otherwise, you'll miss important data. A big development effort on our part was, how do we ensure that the sonde gets all the way down there? We worked closely with the USM team to look at some different ways of doing that, and ultimately came up with a system that would use a set of software parameters to detect slack in the line and know that, ‘Okay, the sound is actually on the bottom; can't get any closer than that.’""When we're looking for the largest effect of hypoxia on the fisheries, you're looking at that layer that's right there near the bottom where all of the bottom dwelling critters are. Obviously if they can't swim up and out of that, then it's going to affect their metabolism and productivity," Thompson explained."By being able to get the sensors all the way down there to the bottom and know with certainty that we got them in that bottom layer of water, and then being able to look at that in real time and say, ‘Yes, we're still detecting low oxygen here, move further south and see if we can find that edge where we're back to oxygenated water again.’ Being able to adjust the mission on the fly and know that we're getting the data that's relevant was absolutely critical."An SP-48 in the water. Credit: USM/SeaTrac SystemsViews captured by the SP-48 while at sea, including inclement weather and a wildlife spotting. Credit: USM/SeaTrac SystemsPhase Two and BeyondDuring phase two, USM deployed multiple SP-48s simultaneously, overseen by a single shore-based operator. The team collected 123 verified hypoxia data points thanks to extended endurance, rapid adaptive sampling and platform reliability, even in challenging Gulf conditions that included a tropical weather system passing through the operational area."One of the things we really have been moving towards each time is improving the integration of sensors and improving that data flow," Thompson said. "Phase one was very much testing that can be done; phase two was improving the way it was done. That included things like more rapid turnaround on the data flow side of things, getting that data from the sensor to the boat, and from the boat over satellite to our system so that we could share that with NOAA in real time as we were going."Another difference, Thompson pointed out, was that the sensors were developing at their own pace, meaning new features could be taken advantage of to further advance data collection. "AML Oceanographic, the company that makes the profiling instrument, has developed a wireless charging ability for it," added Boeschenstein. "Traditionally, we would have to balance, 'We're going to turn the sonde on, collect the data, pull it off, and then put it back to sleep,' which would make it challenging and eventually it runs out of battery. It limits what you're able to do with it." When AML Oceanographic rolled out this new capability, the USM team didn't need to swap out fresh batteries part way through, creating the potential for extended surveys over longer durations."It's a safety issue, too," Thompson added. "You're removing people from having to go service a vehicle out at sea, which in itself is a precarious stance."Tracking the paths of USVs. Credit: USM/SeaTrac SystemsSeaTrac SP-48 in the Gulf. Credit: USM/SeaTrac SystemsLooking forward, the team hopes for another summer of data collection, aiming to add a third SP-48 to the lineup. On the data processing side, the researchers continue to develop automation to include additional quality control steps and are looking to add a 3D model of dissolved oxygen for the entire survey area.A phase three would further the work of phases one and two, collecting critical hypoxia data and highlighting the use of USVs in offshore data collection and monitoring. Even more, this project showcases something less commonly observed—how incremental technological updates, such as wireless charging, energy management, and sensor payload, can be integrated in real time to modernize and advance research.Hobie Boeschenstein. Credit: USM/SeaTrac SystemsJames Thompson. Credit: USM/SeaTrac SystemsWatch the full video on Marine Technology TV.