A new device for sampling waters in shallow ecosystems

Abstract

A set of equipment has been designed to take water samples by aspiration at varying depths in shallow ecosystems. The depths sampled can be freely selected within a range of accuracy of 1 cm. The equipment is portable and can be handled from a boat or from the shore, at points up to 20 m away from the sampling location. A study was made of the accuracy of temperature and dissolved gas content of samples obtained using this device. With respect to the gas analysis, there was no serious loss of gas from the samples as long as they aspirated under a reduced pressure <400 mm Hg. This system enables the collection at a rate of 10.4 l h-1 when the apparatus is placed about 2 or 3 m above the surface of the ecosystem under investigation. The error which occurs in the temperature reading is a function of the differences in temperature between the mass of water sampled and the area surrounding the intake tubes. For differences of around 1°C the error is <0.1°C. Some modifications of the equipment are also suggested in order to simplify the operations necessary to take samples for dissolved gas measurement. Also proposed is a system of on-line filtration useful for quantitative phytoplankton or suspended solid content determinations in the samples. © 1987.