Biodiversity monitoring at one of the UK's Offshore Seaweed Farms

Field Update from Bideford Bay

Our recent field deployment in Bideford Bay marks the first phase of a multi-year study aimed at assessing the ecological impacts of integrated seaweed and shellfish aquaculture. This work is part of our effort to quantify the ecosystem services—such as biodiversity support, water quality improvement, and carbon sequestration—delivered by the Blue Forest concept developed by Algapelago Marine Ltd.

The Blue Forest Concept: Integrating Aquaculture with Ecosystem Services

The Blue Forest is a marine nature-based solution that combines regenerative seaweed and shellfish farming. In doing so, it aims to:

• Enhance Biodiversity: Multitrophic systems can create new habitats and encourage species richness. Evidence from similar projects suggests that combining seaweed and shellfish aquaculture may support diverse marine communities (Duarte et al., 2017).

• Improve Water Quality: By absorbing excess nitrates, phosphates, and even heavy metals, these systems may contribute to water detoxification. Accurate measurement of these parameters is crucial, especially as nutrient trading schemes (for phosphorus and nitrates) and natural capital markets develop in the UK and Europe (European Commission, 2020).

• Sequester Carbon: Seaweed cultivation has been identified as a potential method for carbon sequestration, offering a pathway to generate carbon credits within emerging carbon markets (Mcleod et al., 2011).

The Blue Forest concept: A de-facto Marine Protected Area enhancing biodiversity, restoring the seabed, and absorbing carbon while supporting sustainable aquaculture and local jobs. Image © Algapelago

Such integrated systems could play an important role in meeting future marine net gain policies by providing measurable ecological benefits that support sustainable aquaculture practices and local economies.

Our Monitoring Approach and Tools

Our monitoring approach includes:

• Passive Acoustic Monitoring (PAM): The Chelonia FPOD Hydrophone is positioned at the lowest point of our sensor array to capture cetacean clicks—from dolphins to whales—in a frequency range optimized for these species. This continuous acoustic data helps assess both the relative abundance and behaviour of key marine mammals, which serve as indicators of ecosystem health (Pieretti et al., 2020).

• Programmable Underwater Cameras (PEBL SubCam): Deployed along the sensor string, the SubCam records periodic videos and images of fish, crustaceans, and benthic organisms. A separate, surface-mounted camera monitors the settlement of algae and molluscs on a reference rope. This dual setup allows us to capture changes in species composition and habitat structure over time.

  
  

• Additional Sampling Techniques: Complementary water quality tests—including measurements of salinity, pH, and concentrations of nitrates and phosphates—are conducted alongside chemical analyses for toxins and heavy metals. We also use environmental DNA (eDNA) sediment sampling to help document the presence of species that might not be captured by visual or acoustic methods.

A SUBCAM2 being deployed from the side of a vessel in Bideford Bay. The frame has weighted arms giving the rig good stability on the seabed in storm conditions.

Implications for Natural Capital and Policy

In the UK, there is a growing policy interest in marine net gain—the concept that new marine developments should achieve a net positive impact on biodiversity. Reliable monitoring data will be essential in:

• Validating Ecosystem Benefits: Quantitative evidence of improved water quality, increased biodiversity, and carbon sequestration can help secure the inclusion of aquaculture within marine net gain policies.

• Facilitating Natural Capital Markets: As the UK continues to explore mechanisms for trading ecosystem services (e.g., phosphorus and nitrates credits) and carbon sequestration, robust environmental data will be key to establishing fair and effective market values.

Our ongoing work aims to provide policymakers and industry stakeholders with the technical evidence needed to consider integrated aquaculture as a viable option for enhancing marine natural capital. So watch this space! Meanwhile, here is a video clip showcasing some of the resident fish species we recorded during our deployment.

This footage shows some snippets of footage from the seabed in Bideford Bay at about 20m depth at Algapelago's seaweed farm. Footage was recorded on a PEBL SUBCAM Custom schedule camera where videos were recorded for 2minutes, 3x daily for 3 months in Autumn 2024.