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Karst streams represent special lotic habitats. An important characteristic of karst streams in this study is the formation of tufa from calcium carbonate precipitation and the development of various tufa habitats (underwater barriers, waterfalls, cascades, channels, fast flowing streams). Some authors suggest that aquatic biota of tufa habitats (cyanobacteria, bacteria, diatoms, algae, aquatic insects, mosses) affect tufa formation by their physical ability of accumulation, retention and encrustation of particulate organic and inorganic matter, and alternately by the chemical effects of photosynthesis. Through CO2 uptake and out-gassing, photosynthesis as well as waterfall effects (accelerated flow velocity, enhanced air-water interface) cause supersaturation of water with respect to carbonate minerals followed by precipitation of calcite, following the reaction: Ca2+ + 2HCO3- → CaCO3 (solid) + H2O + CO2 (gas)↑ . The aim of this study was to evaluate seasonal patterns of macroinvertebrate drift and transport of particulate organic and inorganic matter in the karstic Plitvice Lakes hydrosystem in relation to hydrochemical characteristics associated with tufa formation. Results show that lower temperatures and flow velocities, accompanied by lower water turbulence and decreased CO2 efflux, seasonally change carbonate hydrochemistry that favours calcite (tufa) dissolution. Higher decomposition of tufa deposits has an equivalent effect on the removal and downstream transport of mosses and particulate organic and inorganic matter within the barrage system, while drifting macroinvertebrates only partially follow this pattern. |
