Macroalgae 2024 - 2025 Participants:
| Organisation | Opportunistic macroalgae cover ring test (OMC-RT) | Opportunistic macroalgae biomass ring test (OMB-RT) | Country |
| Abrehart Ecology | 1 | - | UK |
| AFBI | 1 | - | UK |
| Cyfoeth Naturiol Cymru/Natural Resources Wales | - | 2 | UK |
| DAERA Environment, Fisheries and Marine Group Laboratory | 1 | 1 | UK |
| Environment Agency | 6 | 5 | UK |
| Estonian Marine Institute | 1 | 1 | Estonia |