Mesocosms: Bridging the gap between in situ and laboratory studies

Abstract Experimental research on aquatic communities in changing environments is challenging. Controlled laboratory experiments can neatly tie cause to effect and allow for a mechanistic understanding of physiological as well as genome‐based processes, but can be of limited ecological relevance. In situ observations can address more complex scenarios but often remain descriptive and difficult to replicate. These challenges have recently led to renewed interest in mesocosm (enclosures of water or benthic areas) research. The use of small‐scale, large‐scale, and in situ mesocosms has provided vital insights into the responses of aquatic communities to climate change and its repercussions, from streams and lakes to coastal and polar ecosystems. Mesocosm experiments have also proven a crucial tool to address how results from individual laboratory experiments on single organisms can translate to the community or ecosystem scale.