1 November 2025.
Tracking Recovery: Monitoring Sussex Bay’s Marine Life.
I’m Alice Clark, a PhD candidate at the University of Sussex. Over the last four years, I have been part of a research team monitoring marine biodiversity.
As part of my PhD research, I used two main methods to monitor how marine life is responding: Baited Remote Underwater Videos (BRUVs) and environmental DNA (eDNA).
BRUVs are metals structures mounted with cameras and a small bait canister. We lower them to the seabed at 30 different sites across Sussex Bay and leave them to record for an hour. Once retrieved, we review the footage to identify the species attracted to the bait and assess the type of habitat present at each site, whether it’s rocky or sandy, covered in seaweed or bare.
The eDNA method works differently, here we collect species data without ever seeing them! eDNA surveys involve collecting a sample of water and analysing the genetic material that species leave behind in the environment, for example from shedding scales or excreting mucous or faeces; these act like invisible fingerprints in the water. eDNA can often detect rare or well camouflaged species that are hard to see on camera, while BRUVs reveal how species behave and interact with their habitats. Together, these two methods give us a detailed picture of underwater life.
Figure 1 below shows a diagram of a BRUV rig and eDNA sampler to illustrate the biodiversity monitoring techniques used in Sussex Bay. (A) is the right hand camera (B) the left hand camera, (C) is the habitat camera facing the back of the rig, (D) is the bait canister. (E) is a Kemmerer sampler used to collect a sample of water for eDNA analysis.
Monitoring marine biodiversity gives us an insight into how ecosystems are responding now that trawling has stopped. By tracking which species are present, how abundant they are, and how healthy their habitats look, we can detect signs of recovery. For example from the return of commercial fish to the growth of sensitive habitats like mussel beds and kelp forests. These data don’t just measure changes or recovery; they guide restoration efforts and help ensure future policies are grounded in science.
Although the data are still being analysed, we’ve already recorded over 80 different vertebrate species across Sussex Bay. We’re also beginning to see subtle shifts in the structure of fish communities over time. However, it is still too early to know whether these shifts are true signs of recovery. In ecological terms, five years is very short; recovery takes time. But with continued monitoring, we hope to see stronger signs of biodiversity returning in the coming years.
Continuous monitoring is essential because it tells the real story of recovery. Marine ecosystems are naturally dynamic, changing with the seasons and years. Long-term studies allow us to tell whether we’re seeing natural variation or genuine signs of improvement. Each dataset we collect adds to a growing understanding that helps scientists, local councils, and communities work towards a thriving bay.
This work is also part of a wider collaboration, involving the Sussex Kelp Recovery Project, Natural England, Sussex Bay, and many other partners. By combining efforts, we can monitor not just biodiversity, but also carbon capture, sedimentation, and habitat structure, all work that colleagues are currently working on, helping to build a complete picture of how the Bay is recovering.
Ecosystems have an incredible ability to bounce back when given the space and time. Through ongoing monitoring and collaboration, we’re learning how to help them do just that: ensuring that Sussex Bay remains a vibrant, resilient home for marine life and a source of pride for our coastal community. The insights gained here could also help guide similar trawling bans and restoration efforts elsewhere, showing how evidence-based management can bring real recovery to our coastal areas.
Thank you Alice for everything you are doing to help nature recover. Our next blog will be written by Toni Finnimore, Founder of The Social Society, bringing people together to do good.
