Andrzej Kołodziejczyk

The responses of littoral invertebrates to eutrophication-linked changes in plant communities

The decay of submerged macrophytes in lakes of high trophic level drastically limits the extent of habitat available to littoral invertebrates. The loss can be partially compensated by growth of filamentous algae. Our results show that macroinvertebrates typically associated with submerged macrophytes as well as planktonic crustaceans and rotifers occurred within algal mats at high densities.Aggregations of filamentous algae are usually short-term, with frequent appearances and disappearances. The rate of colonization of algal mats by invertebrates is rapid. In locations with a high degree of water exchange, animals colonize both living and decomposing algal mats at a similar rate, but in sheltered habitats, decomposing filamentous algae are colonized by a smaller number of animals.Comparison was made between the occurrence of invertebrate macrofauna on Chara spp., Potamogeton perfoliatus, P. lucens and Myriophyllum spicatum in several lakes. Although these macrophytes differ visibly in morphology and phenology, the number and composition of macroinvertebrates during summer was associated more closely with trophic state of a lake than with plant species.

Water bodies of a city park as habitats of rare, protected and alien species of molluscs

Representatives of fifteen species of gastropods and ten taxa of bivalves were found in five small water bodies in Skaryszewski Park in Warsaw. They included Sphaerium rivicola (Lamarck) and Anodonta cygnea (Linnaeus) (empty shells only) which are very rare in Poland, as well as three alien species – Dreissena polymorpha (Pallas), Physa acuta Draparnaud and Menetus dilatatus (Gould). The first of the alien species may have been brought by humans and by waterfowl which is numerous in the Park, the second probably by birds alone. Bithynia troschelii (Paasch), recently elevated to species rank, was also recorded. Despite the similar water chemistry, the species composition and dominance structure of molluscs were greatly diversified both among the studied neighbouring ponds and within the largest of them – Lake Kamionkowskie. Two smallest ponds, emptied for winter, were inhabited only by snails. The diverse occurrence of molluscs might be an effect of different stability of particular water bodies and within Lake Kamionkowskie – of local accumulation of large amounts of organic matter (fallen leaves) on the bottom.

Subtractive moire patterns of identical grids

Derived in the comunicate formula allows to find equation of basic grid for desired moire pattern and kind of displacement. As an illustration few examples of potentially practical application are given.