Mussel reefs serve as important marine habitats and need protection. But how do we map the marine areas with the valuable mussel reefs? A remotely operated vehicle, ROV, has great potential according to a Master's thesis from DTU.
An underwater remotely operated vehicle proves to be a viable tool to go map mussel reefs in need of protection. ROV, short for ‘remotely operated vehicle’, has been tested and discussed as a future tool for mapping biogenic mussel reefs in a Master's thesis by Michelle Melin. Recently, she graduated from Aquatic Science and Technology.
This robotic approach to surveying mussel reefs in the Roskilde Fjord is very new – it only goes back to a DTU Aqua project in 2021.
Read Michelle Melin’s thesis, Citizen science mapping of mussel reefs: Development of a toolbox for local fishermen
Michelle Melin made an agreement with the Danish engineering company EIVA that produces ROV technology to borrow a device for one month. With support from two local fishermen who also provided boat access, Michelle conducted the ROV testing at a site in Roskilde Fjord, Selsø Hage, where blue mussels had been registered, last summer.
"I truly hope to continue working with ROV’s in the future. It is a technology that can help biologist, environmental managers and scientists understand life in the ocean and it has a lot of potential."
Michelle Melin, MSc Eng in Aquatic Science and Technology
Operating a ROV is challenging in the beginning as you operate it from a moving platform, a boat, Michelle explains:
“As the ROV is below the surface, you mainly track it from the PC, so you need to understand how the vehicle behaves and how to control it. I practiced the basic control functions in DTU’s Autonomous SystemsTest Arena, ASTA, and at a harbour site, which was very useful before going out on the sea.”
The main purpose of Michelle Melin’s thesis was to test how and if a remotely operated vehicle, ROV, could be used as a tool for mapping biogenic reefs by local fishermen/citizens:
“Citizen science projects can be designed in many different ways, but this would be a contributory citizen science project, where citizens primarily contribute to data collection. However, due to a number of technical challenges, it was deemed that the drone is not the ideal citizen science mapping tool at this stage.”
Three larger ROV surveys were successfully conducted in Roskilde Fjord and are also presented as a part of Michelle's thesis. In addition to testing how ROV can be used to map and document biogenic reefs in a cost-effective way by involving locals, the thesis investigates the previous marine mapping of biogenic reefs in Danish Natura 2000 sites.
Important marine habitats
Mussel reefs or biogenic reefs are considered crucial in marine conservation because they serve as important habitats for a variety of marine species. They provide shelter and nursery grounds for several fish species, support a range of benthic invertebrates, improves water clarity and have a stabilizing effect on the sediment.
According to the EU Habitats Directive, Denmark is obliged to protect biogenic reefs, if they can be classified as the habitat "Reefs 1170".
In 2018, a Danish definition of biogenic reefs was published. It presented four criteria for reef size, degree of coverage, stability and associated species community. In her thesis, Michelle Melin states that since then, no biogenic reefs have officially been mapped, and that no standard procedure exists for how to meet the criteria.
According to Michelle Melin there are many different ways to map habitats using different tools. It’s all about which scale and which degree of detail you want.
But fundamentally the big question was how do you survey large areas to identify these biogenic reefs?
The question was adressed by Jon C. Svendsen, senior researcher at DTU Aqua, in 2021 when he started a project to study the possibility of using ROV-technology for mapping and identifying biogenic mussel reefs.
The project was requested by local fishermen from the organization Gershøj Fritidsfiskerforening. The fishermen were curious about marine habitats available in the Roskilde Fjord, which is a Natura 2000 area. On this basis, Jon C. Svendsen decided to start the project.
Michelle Melin was part of Jon Christian Svendsen's team, and so the interest for ROV as an underwater surveillance tool started.
This is where the first steps were taken towards fulfilling the obligation to map and protect biogenic reefs within relevant Natura 2000 areas, the largest network of protected areas in the world.
“I truly hope to continue working with ROV’s in the future. It is a technology that can help biologist, environmental managers and scientists understand life in the ocean and it has a lot of potential. It is a great way to obtain visual data of organisms and habitats, which paves the way for many interesting analyses,” says Michelle Melin.
Asked about how she imagines her professional future right now as a newly graduated MSc Eng in Aquatic Science and Technology, Michelle Melin says:
“I have a big interest in doing marine field work and I hope I get the opportunity to use my acquired skills from my Master's in Aquatic Science and Technology to work with marine science and nature management.”
PHOTO: Private
Watch video about the project