katrinteubner

field sampling methods

Lake Mondsee, Austria, 2000
(insets - top: swimming pond, Austria, 2006; bottom: Bergknappweiher, Germany, 2001):
Various types of water sampler to take samples from certain depths are shown here. SCHINDLER sampler is displayed in the main photo (left, named after the Canadian limnologist D.W. Schindler), UWITEC water samplers in both insets. These samplers are operated in the open position when lowered down-flow to the sampling depth. The hinged-lid on top and bottom of the sampler seals when the water flow is turned upward to move the sampler back to the surface and provides thus the sample taken from a certain water depth.
The commonly known ‘RUTTNER sampler’ - this standard water sampler is named after the Austrian limnologist F. Ruttner - looks similar to the UWITEC water sampler shown here, but is closed at a cetrain sampling depth by a falling weight.
Other water samplers are even successively filled up when left gradually the water column down. These are depth-integrated samplers, which can be operated mechanically. During lowering the sampler, the container enlarges while moving the lid by a smooth operated chain and water flows successively in the sampling container with increasing depth (syringe-like operated water sampler). Other constructions of depth-integrated samplers are built by a pear-shaped glass bottle, which is gradually filled up with depth by underwater pressure balance (SCHRÖDER sampler, named after the German Limnologist R. Schröder).Lake Mondsee, Austria, 2002:
GERVAIS tube sampler (named here after F. Gervais who is a German limnologist, see 'close-interval tube sampler of 2 m height' in Gervais 2003 R). This particular tube sampler can be used for taking an integrated sample over a water column of 2 m in certain vertical depths, e.g. in the epilimnion, metalimnion or hypolimnion. It further has the advantage to take sub-samples within the 2 m water column of the tube. The photo shows the use of this tube sampler during the workshop of ‘high-resolution measurements in space and time in Mondsee on plankton community’ (‘HighMoon’). A simple crane connected with a winch can also be seen on the photo. Winches and calibrated ropes or cables are commonly used for depth profiling to operate samplers and multiparameter meters.
Tube samplers are also common for taking depth-integrated samples from the top surface layer of shallow lakes. Such simple but precise and reliable working water-surface sampler is just a 1.5 m plastic tube and can be easily operated by hand and without the use of winches. The tube is lowered vertically into the water until it is filled up with water. After the tube is sealed on the upper side with a rubber stopper by hand, it can be pulled out of the water. The tube needs then to be emptied immediately into a prepared sampling container - just by a slight lift-up of the rubber stopper.

On this the freshwater page, some methods used for field sampling or lab treatment will be described. Sampling and also treatment refer mainly to the phytoplankton and related issues as always on this website. For this reason, the procedure of counting phytoplankton from the water sample will be included. Besides a more detailed description of some phytoplankton taxa, a list of the cell dimensions of common phytoplankton species will be provided.

Topics related to the sampling procedure are described in the Preface S and on pages about lake Mondsee S and pond Bergknappweiher S of the lakeriver-website. An appropriate sampling concept is the first step to finally get reliable data assessing an ecosystem.
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According to a governmental initiative in Ireland, just to give the reference from one country, volunteers were encouraged doing surveys in streams and lakes in their close neighborhood (sampling and bio-monitoring). Such a campaign can indeed help to regenerate a wide-spread and reliable monitoring information of the current water quality in nature. In turn, local people could benefit too and become more aware of the surrounding nature in this way. Far from such campaigns also individual people can be interested to investigate their own wildlife pond S in the garden, their larger basins of a ‘natural’ swimming pond S system or the wildlife Wood pond S and lake nearby in the meadow. Valuable information about the water quality can indeed be gathered by a rather simple scheme of easy to measure parameters that are recorded in a bi-weekly or monthly sampling interval. Why this is worth doing, what results can be expected and how to manage the measurement, will be also explained later on this page. It is even suggested here to keep such easy monitoring for  ‘wild-life garden-ponds’ as simple as possible, in case of studying running and stagnant freshwater ecosystems the methods and concepts of advanced limnology are strongly recommended.

Poyang Lake, China, 2011:
In addition to regular phytoplankton samples also phytoplankton net-samples are taken. The water is taken with a water sampler from a certain depth and is thereafter passed through a plankton net of the defined mesh size. In this subtropical lake, gloves must be worn while sampling to avoid skin contact with the water and hence an infection with parasitic trematodes (schistosomiasis, bilharzia). Danube River, downstream from Iron Gates, Romania, 2005:
An easy way to take a phytoplankton net-sample from surface water. Some water volume just passes the plankton net of 10 µm mesh size to get here enough material for microscopy. For many reasons such 'metal-bucket-sampling' would be by far not appropriate for taking samples for chemical analyses.
During regular sampling, samples are taken with samplers shown in figures above. Phytoplankton samples are filled into small bottles (100 mL) and fixed with Lugol's solution for preservation. Later in the lab, the phytoplanktonsamples are quantified by microscopy. Here, algal cell abundance and biovolume is determined using sedimentation counting chambers under the light microscope. The Phytoplankton biovolume can be converted into fresh biomass. Both quantitative parameters are used an indicator of the water quality and productivity of a lake (Teubner et al. 2023, R).