Scientists from the University of Silesia in Katowice, who have been cooperating with the Upper Silesian Water Supply Company for several years, participated in the research cruise on the lake Goczałkowickie. During the cruise, they took a series of photographs of these organisms.

"We encountered relatively large clusters of freshwater sponges in the lake Goczałkowickie. They are present in several places. For this area, it can be said that these organisms are fairly large" - told PAP Jerzy Karczewski of the Faculty of Biology and Environmental Protection the University of Silesia in Katowice.

Karczewski added that the presence of freshwater sponges in reservoirs, is one of the tests for the purity of water. "Their presence in water indicates its purity and abundance of plankton, and it is an indication that the reservoir is well suited for fish farming" - said the Upper Silesian Water Supply Company spokesman Piotr Biernat.

Sponges are among the oldest multicellular organisms (they resemble plants more than animals). Several thousand species are known, of which more than a hundred occur in fresh water. "In Poland they reach several tens of centimetres in height or diameter, depending on the shape that adapts to the substrate. The coloration is usually grey-brown or yellowish, and with strong exposure - greenish" - informed the scientists.

Sponge colonies have the shape of a bush, and they are attached to the substrate. In Poland, sponges usually inhabit the shallows, where the water flow is stronger. "They are sensitive to pollutants, decay products (methane and hydrogen sulphide), as well as toxic substances and oils, which makes them natural indicators of the quality of the water in the reservoir" - reported the Upper Silesian Water Supply Company.

They feed by filtering nannoplankton and mikroplankton (bacteria, flagellates, diatoms, dinoflagellates and protozoa) and dead organic molecules. Many sponges also act as a biofilters, capturing significant amounts of organic suspensions.

Many invertebrates, for example earthworms, feed on Sponges. The surface of sponge colonies can be a habitat of other organisms, including shellfish, and snails.

The research cruise was organized as part of the Integrated Water Reservoir Management and Protection System. This strategic research project, according to Karczewski, includes testing water quality (drinking water) and its use for tourism and recreation.

Goczałkowickie Lake is an artificial water reservoir created on the Vistula River in 1956. It covering an area of approx. 32 km sq. The tank fulfils two basic tasks. The first is the use of its water to supply the population and industry of Upper Silesia (water is taken from the Vistula by the Upper Silesian Water Supply Company and transferred to two treatment stations: Goczałkowice and Strumień and then through the system of main pipelines to local recipients). The tank also has flood control functions. (PAP)

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