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Microbial and classic food web components under ice cover in eutrophic lakes of different morphometry and fisheries management

Kalinowska K., Napiórkowska-Krzebietke A., Bogacka-Kapusta E., Hutorowicz J., Pyka J., Stawecki K., Kapusta A., Chybowski Ł.

Oceanological and Hydrobiological Studies

2017

Vol. 46, No. 3

271--282

The thickness and duration of ice cover are strongly influenced by global warming. The aim of this study was to determine chemical (organic carbon, total nitrogen and phosphorus concentrations) and biological (nanoflagellates, ciliates, phytoplankton, rotifers, crustaceans) parameters under the ice cover in three eutrophic lakes (Masurian Lake District, Poland), differing in their morphometry and fisheries management. All the studied groups of organisms showed high variability over a short time. Taxonomic composition of planktonic communities, except for rotifers and phytoplankton, was similar in all lakes. Nanoflagellates were dominated by autotrophic forms, while ciliates were primarily composed of small oligotrichs and prostomatids. Nano-sized diatoms and mixotrophic cryptophytes were the most important components of phytoplankton and they formed an under-ice bloom in one lake only. Rotifers were mainly represented by Keratella cochlearis, Polyarthra dolichoptera and Asplanchna priodonta. Among crustaceans, copepods clearly dominated over cladocerans. Our research suggests that winter was a very dynamic period. In the under-ice conditions, pelagic organisms were strongly dependent on each other. The shallow lake and the deeper, small lake differed significantly in nutrient and chlorophyll concentrations, ciliate and phytoplankton biomass and the ratio of autotrophic to heterotrophic biomass. These results suggest that morphometric parameters may affect planktonic organisms during the ice-covered period.

Anthropogenic changes in properties of the water and spatial structure of the vegetation of the lobelia lake Lake Modre in the Bytów Lakeland

Kraska M., Klimaszyk P., Piotrowicz R.

Oceanological and Hydrobiological Studies

2013

Vol. 42, No. 3

302--313

Lake Modre is a lobelia lake. Numerous typical plant species occur here, including Lobelia dortmanna, Littorella uniflora, Isoetes lacustris, and Sphagnum denticulatum. They develop the following associations: Lobelietum dortmannae (Oswald 1923) Tx. ap. Dierss. 1972, Isoetetum lacustris Szańkowski et Kłosowski 1996 n.n., and a community with Sphagnum denticulatum Brid. In 1991, the water of the lake was characterised by low concentrations of nutrients and calcium, acid reaction (pH<5), and Secchi depth visibility of 12 m. Following fry stocking in the lake in 1993 fish farming took place until approximately 1996. During this period the water quality in the lake changed radically in physiochemical terms. Water transparency decreased. Thermal and oxygen stratification developed, with oxygen deficits in the near-bottom layer. Concentrations of nutrient elements increased. Drastic long-term changes were observed in the spatial and quantitative features of the lake vegetation. These particularly related to the instability of Lobelia dortmanna, and the diminishment of the phytocoenosis of Lobelietum dortmannae. Consequently, the phytocoenosis occurred only in the shallowest part of the phytolittoral. L. uniflora expanded, increasing its occurrence annually. Significant fluctuations in quantities of S. denticulatum occurred, correlated with changes in physiochemical water parameters, but shifted in time.

Effects of grass carp introduction on macrophyte communities in a shallow lake

Krupska J., Pełechaty M., Pukacz A., Ossowski P.

Oceanological and Hydrobiological Studies

2012

Vol. 41, No. 1

35-40

In 2002, 2005 and 2007 vegetation and physicochemical properties of pelagial water were investigated in a shallow mid-forest lake. In 2002, the highest phytocoenotic diversity was recorded; charophytes and vascular submerged macrophytes formed their own extensive communities. After stocking with grass carp (Ctenopharyngodon idella Val.) in 2002, reduction of water transparency, as well as changes in qualitative and quantitative composition of macrophyte communities were observed. Submerged vegetation declined during subsequent growing seasons. Charophyte meadows vanished first. The introduction of grass carp appeared to be a potential trigger for the rapid changes observed in the vegetation.