Discourse &Communication, Ahead of Print.
In this article I claim that online Citizen Science projects are exemplars of a digital genre that acts as text and medium. To support this claim I apply a previously proposed two-dimensional genre analytical model and develop empirical procedures to identify how ‘communicative purpose’ is realised by functional units/links, which in turn are realised by rhetorical strategies (verbal and visual) in two dimensions, the reading mode and the navigation mode. Empirical data show that this genre fulfils a set of distinct communicative purposes, namely to build credibility and trust in scientific research, to make specialised contents accessible to audiences with different levels of scientific literacy, to convey emotion and to build and maintain citizen-volunteers’ engagement. Such multifunctionality fulfils the social exigence of the genre, that is, supporting participatory science. The study contributes to the empirical characterisation of non-linear, multimodal genres taking into account the roles of text producer and text receiver.