Development of a water sampler of intermittent suction with an evacuated chamber (WISE)

In oceans, water column can be stably stratified and the biological constituents of a water column, such as bacteria, phytoplanktons, and micro-zooplanktons, are relatively unevenly and vertically distributed. To observe the vertical profile of a stratified water column, in situ sensors, such as CTD and fluorometers, are often used in the field; however, field analyses are time consuming, making preprocessing followed by water sampling indispensable. Conventionally, water sampling by Niskin or Van Dorn samplers is performed at predetermined depths. If the target organisms aggregate to form thin layers, water may not be sampled well if the layer is thinner than the vertical sampling interval. Another approach for fine scale measurements is to employ numerous arranged syringes that simultaneously suck water; however, in this approach, water between the arranged syringes is not sampled. Therefore, vertically continuous sampling is required to accurately observe the vertical distribution of marine organisms. Here, we present a new sampler that sucks water using a pressure gradient, in which ambient water is sucked and transferred to one end of a tube with the other end connected to a vacuum chamber. To maintain the thickness and shape of the thin layer, gentle suction is required. In fact, suction flow generated with the sampler produces smaller turbulence than conventional samplers.