Chemical analysis of water
samples was based on standard methods for
the examination of water and waste water
(Greenberg et al., 1998). In addition,
composition of phytoplankton and
zooplankton was studied. 10 L of water
were passed through a phytoplankton net
(mesh size 20 μm) and a zooplankton net
(mesh size 60 μm). Then, plankton samples
were transferred into plastic bottles and
preserved using 70% ethanol before they
were examined under a microscope up to
species level.