The Big Seaweed Search: Evaluating a citizen science project for a difficult to identify group of organisms

Abstract The Big Seaweed Search invites people to survey UK seashores for 14 conspicuous seaweeds. The science investigates: (i) impact of sea temperature rise; (ii) spread of non‐native species; and (iii) impact of ocean acidification. Survey data submitted between June 2016 and May 2020 were analysed to evaluate and explore project directions in relation to citizen science project development. Of the 378 surveys submitted, 1,414 people participated, contributing 1,531 person hours. Surveys were undertaken around the UK, with the highest proportion (46.7%) in the south west and the lowest (3.7%) in the north east. After data verification, 1,007 (54%) records were accepted. Fucus serratus had the highest number of entries correctly identified (66%) and Undaria pinnatifida the lowest (5%), inferring that at least some seaweeds can be difficult to identify, although the overall misidentification rate was relatively low (c. 15%). Apart from Alaria esculenta , U. pinnatifida and Saccharina latissima , the large brown seaweeds were abundant on at least some shores. Non‐natives Sargassum muticum and Asparagopsis armata , were band‐forming but in low numbers. Coralline algae, whilst band‐forming on some shores, were most commonly patchy or sparse in abundance. Revisits, i.e. repeat surveys, at the same site with an interval of at least 1 year, are relatively low, with 18 sites revisited once and three sites revisited twice. Currently, data are insufficient to determine whether any changes in abundance could be detected. This study highlights areas where project developments can enhance data quality and quantity, e.g. better identification resources, training programmes for dedicated volunteers, and an annual focus week of activities. The project framed around climate change impacts, aims to raise awareness of the ecological importance of, and threats faced by, this understudied habitat and introduce conservation concepts including the need to protect common species showing signs of decline.