engleski

ALGAE IN FRESHWATER ECOSYSTEMS OF CROATIA

Researches of algae in freshwater ecosystems of Croatia have been conducted since the beginning of 20th century. However, only within the last decade they have been systematic ecological and biocenological researches. Based on the results of the research, qualitative compositions of phytoplankton, periphyton and phytobentos communities as well as their succession in many freshwater ecosystems in Croatia have been determined. Great abundance of species is characteristic of natural ecosystems whilst artificial lakes and reservoirs are quantitatively poorer. The role of algae in transformation of energy during the primary production process has been determined as well – it is greatest in summer and lower in parts of ecosystem burdened by large quantities of organic sediment. Primary production of plankton in fish pond ecosystems has been stimulates by addition of nutrients, and continuous research of feeding relations in phytoplankton-zooplankton-fish chain has been made. Accelerated eutrophication has been noted as a consequence of anthropogenic influences in natural ecosystems (NP Plitvice Lakes and Special Zoological Reserve Kopački rit). Qualitative and quantitative compositions of algae, especially indicators of certain degrees of saprobity, have regularly been monitored through saprobiological analyses. A lower degree of saprobity has been determined for most water resources of Croatia, while eutrophic lakes, fish ponds and rivers at points of direct pollution influence have higher degree of saprobity. Significant role of algae in the process of travertine growth has been proven as well. Mucopolysaccharide excretions of periphyton bind calcite crystals and initialize the process of travertine growth. The results of previous research point out the primary role of algae in energetic and ecological stability of freshwater ecosystems in Croatia. Thus, further comprehensive, continuous and methodologically synchronous investigations are required in order to continuously protect Croatian freshwater ecosystems.

algae; freshwater ecosystems; Croatia

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