We investigate the development of scientific content knowledge of volunteers participating in online citizen science projects in the Zooniverse (http://www.zooniverse.org). We use econometric methods to test how measures of project participation relate to success in a science quiz, controlling for factors known to correlate with scientific knowledge. Citizen scientists believe they are learning about both the content and processes of science through their participation. We don't directly test the latter, but we find evidence to support the former — that more actively engaged participants perform better in a project-specific science knowledge quiz, even after controlling for their general science knowledge. We interpret this as evidence of learning of science content inspired by participation in online citizen science.

Online citizen science projects have demonstrated their usefulness for research, however little is known about the potential benefits for volunteers. We conducted 39 interviews (28 volunteers, 11 researchers) to gain a greater understanding of volunteers' motivations, learning and creativity (MLC). In our MLC model we explain that participating and progressing in a project community provides volunteers with many indirect opportunities for learning and creativity. The more aspects that volunteers are involved in, the more likely they are to sustain their participation in the project. These results have implications for the design and management of online citizen science projects. It is important to provide users with tools to communicate in order to supporting social learning, community building and sharing.

Community-based water monitoring (CBWM) provides essential baseline information on watershed health and engages the public in science, but those involved often encounter barriers to informing environmental management. We conducted qualitative interviews with watershed group coordinators and government counterparts from four CBWM organizations to explore instances where CBWM successfully influenced governmental decision-making. Our findings show that the level of rigor for quality standards, inclusion of volunteers, available resources, and desired goals are important considerations when designing community-based monitoring programs. Integrated program designs that include adequate quality standards and engage volunteers are more apt to maximize resources and realize both scientific and educational goals.

Volunteer water quality monitors represent the intersection between citizen science and environmental stewardship. Understanding what motivates participation will enable project managers to improve recruitment and retention. This survey of 271 volunteers from eight water quality monitoring organizations in the U.S. found the strongest motivators to participate are helping the environment or community and contributing to scientific knowledge. No variation by gender was found, but younger volunteers have different motivations and preferences than older volunteers. Volunteers value the communication of tangible results more than recognition or reward.

This issue forms Part II of JCOM's collection of articles and essays exploring the field of citizen science. Here I introduce the articles in Part II, outlining how they contribute to our understanding of the ways that volunteers participate in citizen science projects, what motivates this participation and what learning arises as a result of participation.

There is growing recognition that effective science communication should not merely focus on addressing scientific literacy but must also open dialogue between scientists and the public, build trust, and increase public interest in environmental research. Citizen science BioBlitzes offer a useful approach for science communicators to address many of these key aims. We explore the BioBlitz concept, learnings and outcomes based on a case study of a BioBlitz held in Sydney, Australia. We found that participants valued learning about biodiversity on the day and importantly, all participants (scientists and citizen scientists) rated interacting and learning from the experience as one of the main benefits.

The participation of non-professionally trained people in so-called citizen science (CS) projects is a much discussed topic at the moment. Frequently, however, the contribution of citizens is limited to only a few narrow tasks. Focusing on an initiative dedicated to the study of the human microbiome, this paper describes such a case where citizen participation is limited to the provision of funding, samples, and personal data. Researchers opted for a crowdsourced approaches because other forms of funding and recruitment did not seem feasible. We argue that despite the narrow understanding of participation in the context of some CS projects, they can address some of the democratic concerns related to scientific knowledge creation. For example, CS and crowdsourcing can help to foster dialogue between researchers and publics, and increase the influence of citizens on research agenda setting.

The academic journal paper has been around for several hundred years and during that time has seen shifts in style and structure. This editorial explores the traditional research paper and considers whether thinking about the research paper as a story, provides insights into style and structure that would make research both more transparent and more readable.

The prevalent lack of research on the interrelations between science, research and popular culture led to the organization of the first International Conference on Science and Research in Popular Culture #POPSCI2015, which took place at Alpen-Adria-Universität in Klagenfurt, Austria, from 17--18 September 2015. The aim of the conference was to bring together not only science communication researchers with an interest in popular culture, but also other scholars, scientists and researchers, artists, media professionals and members from the general public. In this issue of JCOM we present four invited commentaries which are all based on presentations at the conference.

As a result of the large number of media used and a variety of objectives pursued by the various Public Communication of Science (PCS) activities, their evaluation turns into a daunting task. Therefore, a general taxonomy for all the approaches used by PCS could be helpful in order to differentiate their effects and to measure their results. A general format is proposed for a fast and easy evaluation of PCS efforts and to share a common language with all science communicators, who need to easily compare the results of this growing activity.