Daniel Szymański, Julita Dunalska, Bożena Jaworska, Izabela Bigaj, Rafał Zieliński, Ewelina Nowosad
Uniwersytet Warmińsko-Mazurski, Olsztyn
Littoral zone is the first zone of the lake, which directly borders the land and is a barrier to substances flowing from the catchment. It can play an important role in the productivity of the entire ecosystem, with both production and degradation of organic carbon. The aim of this study was to determine the role of phytoplankton in primary production and respiration in the littoral zone, depending on the development of the basin. The research was conducted in the spring, summer and autumn at eight sites of littoral zone with a different level of the direct catchment area development: two sites (1, 2) in the western part of the lake, which is dominated by forests, three sites (3, 4, 5) in the northern part of the basin, dominated by wasteland and private recreational areas, two sites (6, 7) in the eastern, the most transformed by man and one site (8) located in the southern part of the lake near the outflow. The production volume of the primary and respiration were determined by the change of the oxygen concentration in water using the method of "light and dark bottles" exposed for 24 hours in the surface layer of water. The lake primary production was significantly lower in the littoral parts shaded by forest than in sites exposed to the sun, occurring in the northern part of the lake. The highest primary production with simultaneously high phytoplankton biomass was found at the site in the north. The additional factor intensifying the primary production was the nutrient inflow from the recreationally used land. The highest rate of respiration was recorded in not forested sites, located in the northeastern part of the lake, where the autochthonic and allochtonic organic matter was reduced to CO2. The results indicate a dual role of littoral in the metabolism of Lake Kortowskie. On the one hand, the littoral zone supplies the basin in autochthonic organic matter, on the other hand reduces the organic matter which was produced in the water column and was supplied from the catchment. One suspects that the actual primary production in the littoral zone of Lake Kortowskiego was higher because a significant cover the bottom of the macrophytes limited primary production of phytoplankton.
zmienność produkcji; respiracja fitoplanktonu
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