Opportunistic reporting of species observations to online platforms provide one of the most extensive sources of information about the distribution and status of organisms in the wild. The lack of a clear sampling design, and changes in reporting over time, leads to challenges when analysing these data for temporal change in organisms. To better understand temporal changes in reporting, we use records submitted to an online platform in Sweden (Artportalen), currently containing 80 million records. Focussing on five taxonomic groups, fungi, plants, beetles, butterflies and birds, we decompose change in reporting into long-term and seasonal trends, and effects of weekdays, holidays and weather variables. The large surge in number of records since the launch of the, initially taxa-specific, portals is accompanied by non-trivial long-term and seasonal changes that differ between the taxonomic groups and are likely due to changes in, and differences between, the user communities and observer behaviour.

向在线平台提供物种观察的机会报告提供了关于野生生物的分布和状态的最广泛的信息来源之一。缺乏明确的抽样设计以及报告随时间的变化，导致在分析这些数据以了解生物体的时间变化时面临挑战。为了更好地了解报告的时间变化，我们使用提交到瑞典在线平台 (Artportalen) 的记录，该平台目前包含 8000 万条记录。我们关注五​​个分类群，真菌、植物、甲虫、蝴蝶和鸟类，将报告中的变化分解为长期和季节性趋势，以及工作日、假期和天气变量的影响。自最初针对特定分类群的记录发布以来，记录数量激增，