Molecular-biological sensing in aquatic environments: recent developments and emerging capabilities

•In situ samplers and sensors can revolutionise our understanding of aquatic microbial communities.•Current instrumentation has been demonstrated from the coast to deep sea.•'Samplers' collect water and suspended microbes for analysis in a centralised lab.•'Sensors' perform in situ sample processing and analytics using genetic assays.•Emerging capabilities include low cost and miniaturised analytical platforms.

Aquatic microbial communities are central to biogeochemical processes that maintain Earth's habitability. However, there is a significant paucity of data collected from these species in their natural environment. To address this, a suite of ocean-deployable sampling and sensing instrumentation has been developed to retrieve, archive and analyse water samples and their microbial fraction using state of the art genetic assays. Recent deployments have shed new light onto the role microbes play in essential ocean processes and highlight the risks they may pose to coastal populations. Although current designs are generally too large, complex and expensive for widespread use, a host of emerging bio-analytical technologies have the potential to revolutionise this field and open new possibilities in aquatic microbial metrology.