Passive citizen science: social media as a tool for marine wildlife observation

ABSTRACT: It is not new that species occurrence records provided by citizens are valuable contributions to marine research. However, passive citizen science is a recent and promising methodology of crowdsourcing. Here, we review existing studies that used spontaneous posts shared by users on social media to obtain marine wildlife scientific data. We also present a critical analysis of passive citizen science using social media. Specifically, we (1) introduce marine citizen science and (2) analyze the advantages of passive citizen science compared with voluntary approaches. We also (3) present investigations that extracted information and produced knowledge for marine ecology and conservation through passive citizen science, (4) discuss best practices and opportunities, and (5) identify challenges of this approach. Although social media data may have inherent biases and diverse ethical issues, the data volume is generally large, and the benefits of obtaining observations at a low cost and in real time compensate for some shortcomings, which can sometimes be mitigated. Considering that the use of passive citizen science will continue to grow and be part of our daily lives, we expect the current review to be useful for future investigations.