Volume 18 (2018): Edizione 1 (March 2018)

The aim of this study was a recognition of the carbon cycle in a small anthropogenic reservoir located in Wrocław (SW Poland). The research investigated the geochemical processes and isotopic interactions in the water column as well as those between the water column and the sediment. Moreover, an attempt was made to identify the sources of carbon in the studied water body. Observations of temporal and spatial (vertical and horizontal) geochemical trends were the subject of this research. Chemical and isotopic analyses were the main tool used in this study. A total of 49 samples of water, sediment and plants were prepared, with sampling carried out in the period from October 2015 to May 2017. Two periods: autumn and spring were chosen for the study. During the autumn cycle, smaller variations in the values of δ¹³C in DIC were found compared to the spring cycle. The enrichment of dissolved inorganic carbon (DIC) in the heavy isotope during the spring period was caused by the dynamic growth of microorganisms. The process of assimilative reduction of dissolved inorganic carbon by aquatic organisms, which use inorganic carbon in biochemical reactions, occurred in the reservoir. This process led to an enrichment of DIC in the ¹³C isotope. The analysis of the sedimentary organic carbon revealed a greater enrichment in the heavy isotope of carbon (by about 3‰) in April compared to May. This is due to the growth of microorganisms responsible for degradation of sedimentary organic matter and plant detritus. The sediment and the water column were shown to interact through the exchange of carbon.

The zooplankton assemblage of selected wetlands of Assam, India was assessed to deduce the structural variation in the context of water quality parameters. A two year study between 2012 and 2014 comprising of 530 samples from the five wetlands revealed the presence of 46 taxa, 26 Rotifera, 15 Cladocera, 4 Copepoda and 1 Ostracoda, in varying density. The rotifers dominated in terms of abundance (48 ind. cm⁻³) followed by the cladocerans (28 ind. cm⁻³) and the copepods (19 ind. cm⁻³) and showed significant (p <0.05) correlations with turbidity, alkalinity, hardness and phosphate contents of the water samples. The diversity and the richness of the zooplankton showed an increasing trend with the water temperature. Among the different taxa, Brachionus sp. was most abundant followed by Mesocyclops sp. while Beauchampiella sp. was represented in the least numbers. Application of the cluster analysis allowed the segregation of the different zooplankton based on the similarities of abundance in the samples. The water quality parameters like temperature, alkalinity, turbidity, magnesium and calcium were observed to be significant contributors in shaping the zooplankton community composition of the wetlands, revealed through the correlations and canonical correspondence analysis. As an extension, the information can be used in monitoring the quality of the freshwater habitats of the concerned and similar geographical regions, using the zooplankton as the major constituents. The variations in the abundance of cladoceran, copepod and rotifer zooplanktons can be used to understand the mechanisms that sustain the food webs of the aquatic community of the freshwater bodies.

Lake Erenciuc is situated in the Danube Delta (Romania) and was created in the abandoned riverbed of the Sfântu Gheorghe arm. It is the largest meander lake in Romania. During spring–summer, the physico-chemical parameters of water have been measured in seven lake sampling points and one at the Sfântu Gheorghe branch, which supplies the lake through Erenciuc channel. The area around Lake Erenciuc belongs to the category of strictly protected areas within the Danube Delta Biosphere Reserve. The following water quality parameters were measured: temperature (T: °C); pH (pH units); Luminescent Dissolved Oxygen (LDO: mg dm⁻³); Dissolved Oxygen saturation (DO: %); water tension (U: mV); Electrical Conductivity (EC: μS cm⁻¹); Total Dissolved Solids concentration (TDS: mg dm⁻³). The recorded values are easily differentiated across the entire length of the elongated lake path, especially between inflow (upstream) and outflow (downstream). The parameters recorded during the spring–summer period, with high flow rates and high water levels, demonstrate good lake water quality, especially oxygenation. The study also demonstrates that high waters refresh and recalibrate the water quality in isolated lake basins.

Progressing eutrophication of waterbodies requires measures to be undertaken that aim at halting or reversing negative changes in the environment. Chemical restoration is one of the most common methods used for lake treatment, where iron or aluminium phosphate coagulants are applied. However, their chemical qualities pose the risk of acidification and aluminium ion release, which become toxic in acidic conditions. The influence of coagulants on aquatic plants, including charophytes that are very valuable from the ecological perspective, is little recognised. For this reason, the aim of the research was to define changes in the growth pattern of the charophyte Chara hispida under the influence of an aluminium coagulant. The research was carried out in mesocosms (0.8 m³) located in situ in a lake. Polyaluminium chloride was applied once to each chamber in doses of 50.0, 100.0 and 200.0 ml m⁻³. Coagulant concentrations reflected aggressive restoration aimed at precipitation of phosphates, suspension and water colour at the same time. It was proved that the coagulant had inhibited the growth and slightly reduced the length of branchlets, and simultaneously elongated internode cells. Changes in the total length as well as the length of branchlets were caused by a strong pH decrease of the environment which simultaneously induced higher aluminium solubility and toxicity. Elongation of internode cells was caused by reduced light availability, resulting from high water turbidity in the first stage of coagulant’s application, and then from the charophytes’ thallus being covered by a coagulated suspension precipitated from water.

The aim of the study was to determine the influence of urban agglomeration on a small, natural water reservoir which, as a result of the expansion of the city of Poznań, has become an urban lake. In the vegetation period 2015, the chemistry of its water was studied, and in September additional samples of bottom sediments, plants and fish were collected for analysis in order to determine the content of heavy metals. In terms of productivity, no significant influence of the catchment was recorded. In the 1980s the lake was defined as eutrophic, and in 1996 as α-mesotrophic and such a state continues until today. This is the result of protective activity undertaken by its new owner. The adverse influence of the urbanization of the surrounding areas was reflected by the increased content of lead in particular elements of this ecosystem, that is, in bottom sediments, plants and fish muscles.