The collection and analysis of data relating to the natural world by members of the public, often in collaboration with professional scientists, is known as citizen science.

Now research has proven that it can help improve conservation of marine ecosystems in the Mediterranean, and mitigate the impact of the environmental crisis. A study by the University of Barcelona and the Institute of Marine Sciences (ICM-CSIC) has highlighted the scientific rigour of the work carried out by volunteers in assessing the state of conservation of corals on the Mediterranean coast.

The study, published in the journal Environmental Management, shows the improvement in the precision and accuracy of data collected by the volunteers through training.

“With only one training session, they reached values equal to those obtained by scientists,” says Professor Cristina Linares, from the University of Barcelona, who coordinated the research.

The results of the citizen science initiative also warn of the increase in the mortality of coral species at many points along the Costa Brava in Spain. The Mediterranean coral reef, formed by the accumulation of calcareous organisms, is home to more than 1,600 marine species that have been affected by the rise of water temperatures over the last years.

Marine defence

This study was carried out as part of the Atenció Coralls project, promoted by the citizen science platform Observadors del Mar, to train volunteers in the study of the distribution and ecological status of populations of octocorals and hexacorals affected by human disturbances, especially temperature rise. The team compared the data obtained in the Costa Brava by volunteers with different levels of training in sampling procedures, to observe whether there was an improvement after training.

“The data on the assessment of the state of conservation, obtained from the percentage of affected colonies, collected by volunteers who trained for two days, are comparable to the data obtained by the scientists. After only one day of training, the volunteers obtained quite remarkable results from the first sampling,” says Linares.

Key factors in the study are the previous training the volunteers receive and the expert validation of the data before their transfer and analysis.

“The validation process by the experts is essential to guarantee the assessment of the conservation state to be consistent and reliable,” says Laura Figuerola, a researcher at MedRecover, a marine conservation group.

Once the effectiveness and rigour of the volunteers' work had been validated, the researchers analysed all the data obtained. In different areas of the north-western Mediterranean, populations of coral, including soft-coral gorgonians are 'getting worse and worse', according to the study, as the percentage of affected colonies is going from mostly not impacted or lightly impacted in 2012-14, to moderately and severely impacted in the 2015-2019 and 2020-2022 periods.

"These results are similar to those reported in scientific articles, but in areas that had not been studied before, giving an enrichment of knowledge about the conservation status of these species in areas that had not been studied until now," says ICM researcher Joaquim Garrabou.

Expanding sampling

The data of this study were obtained in 2022, but the trips to assess the state of other species continued in 2023, expanding the sampling spots. Last year, the University and Observadors del Mar organised a series of Coralligenous Weekends.

Some 70 volunteers and seven diving centres on the Costa Brava took part, following Atenció Coralls's outreach to assess the impact of heatwaves on more than 10,000 gorgonians — 95 surveys in 16 towns.

Elisenda Franco, from the Club Nàutic Port de la Selva, is one of the people who took part in the conference, she said, "It was a very positive experience. Citizen science is great, because it allows us to mix citizens who are enthusiastic about the sea with scientists, taking advantage of the experience of each one, in my case, as a diver."

For Robert López, a member of the Biology Immersion Club within the University of Barcelona's biology faculty, it is an opportunity "to help obtain data that can be disseminated or published in a scientific article."

Franco said that the training was "very visual and understandable." She added, "It gives you a different view of the sea: now you can see how the gorgonians are and you can see that many of them are damaged."

López, says, "It makes you aware of the impact on the gorgonians and the changes that are taking place under the water due to the warming of the sea".

Both volunteers agreed that it is a way of raising awareness about the reality of climate change and ensuring that this knowledge reaches the public.

"The fact that they told us about it so well, that it was such a motivating experience, makes you try to transfer it to your environment. In a way, it is a step that remains, it is a kind of chain to educate, raise awareness and disseminate what we have learned," Franco concludes.

Depth of research

The first results revealed that, in all the populations that suffered mortality due to the high temperatures over the last years, the white gorgonian was the most affected, with 80% of the populations being severely affected. In the case of the red gorgonian, 50% of the populations were severely affected.

The effects also vary according to depth. In the first 20m, severe damage predominates, between 20m and 30m, moderate damage predominates — corresponding to 30-60% of the gorgonians being affected.

"It is not until we go beyond 30 metres that we find populations with low damage - with less than 30% of the gorgonians affected," the researchers conclude.