Abstract: A field apparatus (also referred to as a “biosampler”) is configured to automatically capture multiple samples of an aqueous medium (for example, water from a lake) and process same to preserve unstable analytes in the field. In this way, a set of samples from the aqueous medium can, for example, be captured at multiple points in time, processed with a biopreservative to preserve unstable analytes (for example, RNA) and then later collected for further analysis. Alternatively, multiple samples of the aqueous medium can be collected and preserved at one moment.