Biodiversity citizen science projects are both valued for their contribution to scientific research and for their impact on participants' science learning and engagement towards the environment. In this paper, we assess the impact of participation in a biodiversity citizen science project (the Spipoll, dedicated to pollinators' monitoring) through the analysis of online interactions within the program's data sharing platform. By drawing on a previous qualitative analysis of the comments exchanged by the participants within this platform, we focus on those comments which share items on aspects of biology and ecology related to the Spipoll program. This sample gathers 2279 comments from 2010 to 2018. We first classified the different constitutive elements from these comments into seven categories following the topics they deal with. We then studied the temporal change in occurrence of each of these topics from 2010 to 2018. We show that long-term participation is associated with the growing expression of scientific procedural skills: formulation of hypothesis and explanation, proposition of new research questions. To our knowledge, our study is the first one that detects the acquisition of such procedural skills in biodiversity citizen science. We also show that long-term participation is associated with the growing attention to natural seasonal cycles. This study finally illustrates the value of the online traces of citizen scientists' activities to analyze participants' outcomes of citizen science. Consequently, it should encourage the development of such online communication spaces within contributory projects, without restricting them to online citizen science.