The Niskin bottle is a (plastic) tube open to the water at both ends. The bottle is attached to a cable and lowered to the desired depth where the bottle is closed with a weigth that slips down the cable (messenger) or electronically. Each end of the bottle is equipped with a cap which is either spring-loaded or tensioned by an elastic rope. The action of the messenger weight is to trip both caps shut and seal the tube. |
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