How accurate is citizen science? Evaluating public assessments of coastal water quality

Citizen science is changing society's contribution to research projects worldwide. Non-experts are no longer just spectators, they are active participants and supporters of scientific work. Using citizen science, that is, data collected by laypeople, the opportunities to collect large-scale data on the environment are increasing. Such community-based and citizen scientific approaches can provide useful tools as local people can be trained to accurately take measurements that can be used in scientific studies. However, little is known about how well volunteer-based non-standard subjective assessments of the environment based on prior experience only and no training compare with scientifically measured estimates of that environment. In this paper, we tested how well measures of coastal water quality assessed by local inhabitants corresponds with objective water quality data collected using scientific instruments. Our results showed that over 70% of the respondents assessed water quality in the right direction and almost 60% were correct in their estimates. We found that socio-demographic factors affect the assessments, but do not markedly improve reliability. We conclude that simple questionnaires can be used to assess general coastal water quality.