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Soft water lakes with isoetids (SLI) are ecosystems prone to degradation due to the low buffer capacity of their waters. One of the main threats resulting from human impact is eutrophication due to agriculture, catchment urbanization and recreational use. In this paper, changes in the water chemistry and transformation of biocoenoses of one of the largest Polish SLI, Lake Jeleń, over the past 30 years are presented. The lake is located within the borders of a city, and a significant part of its catchment is under agriculture and recreation use. The physicochemical (concentration of nutrients, organic matter, electrical conductivity, oxygen saturation and water pH) and biological parameters (macrophytes and phytoplankton) were measured in summer 1991, 2004, 2013 and 2018. Since the beginning of the 1990s, a gradual increase in the trophy of the lake has been observed as indicated by increased nutrient availability, deterioration of oxygen conditions and a decrease in water transparency. The alterations of water chemistry induce biological transformations, in particular, an increase in phytoplankton abundance (4-fold increase of biomass in epilimnion) as well as a gradual reduction in the range of the phytolittoral (from 10 to 6 m), a decrease in the frequency of isoetids, Lobelia dortmanna and Isoetes lacustris, and expansion of plant species characteristic for eutrophy.

Copper mining generates large quantities of waste, tailings, and acid outflows causing long-term environmental impacts and potential threats to human health. Valea Şesei is the largest tailing impoundment in Romania, created by flooding the valley (known as Valea Şesei) of the Metalliferous Mountains (a division of the Apuseni Mountains) with copper mining waste. The present study (i) estimated the total volume of tailings in this area; (ii) screened the concentration of 65 elements (rare earth and platinum group elements, alkali metals and alkali earth metals, transition and post-transition metals and metalloids) and cyanide concentrations in wastewater samples collected from tailing impoundment; (iii) evaluated the toxicity of these water samples using five in vitro bioassays employing human cells isolated from healthy donors and a short-term (1 h) exposure model. The sampled waters were highly acidic (pH 2.1–4.9) and had high electrical conductivity (280–1561 mS cm−1). No cyanides were detected in any sample. Water samples collected from the stream (AMD) inflowing to the tailing impoundment were characterized by the greatest concentrations of alkali metals, alkaline earth metals, transition and post-transition metals, metalloids, rare earth elements, and noble metal group. At other sites, the elemental concentrations were lower but remained high enough to pose a relevant risk. The greatest magnitude of in vitro toxic effects was induced by AMD. Observed alterations included redox imbalance in human neutrophils followed by lipid peroxidation and decreased cell survival, significant aggregation of red blood cells, and increased prothrombin time. The study highlights that Valea Şesei is a large sink for toxic elements, posing environmental and health risks, and requiring action to prevent further release of chemicals and to initiate restoration of the area.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-017-9782-y) contains supplementary material, which is available to authorized users.

Abstract:The results of the latest bathymetric survey of 21 lakes in the Suwałki Landscape Park (SLP) are presented here. Measurements of the underwater lake topography were carried out in the years 2012-2013 using the hydroacoustic method (sonar Lawrence 480M). In the case of four lakes (Błędne, Pogorzałek, Purwin, Wodziłki) this was the first time a bathymetric survey had been performed. Field material was used to prepare bathymetric maps, which were then used for calculating the basic size and shape parameters of the lake basins. The results of the studies are shown against the nearly 90 year history of bathymetric surveying of the SLP lakes. In the light of the current measurements, the total area of the SLP lakes is over 634 hm 2 and its limnic ratio is 10%. Lake water resources in the park were estimated at 143 037.1 dam 3 . This value corresponds to a retention index of 2257 mm. In addition, studies have shown that the previous morphometric data are not very accurate. The relative differences in the lake surface areas ranged from -14.1 to 9.1%, and in the case of volume -from -32.2 to 35.3%. The greatest differences in the volume, expressed in absolute values, were found in the largest SLP lakes: Hańcza

The spatial variation of water transparency of the largest Polish lakes was presented on the basis of documentary material collected by the Voivodeship Inspectorates for Environment Protection as well as university geography departments in the period of 1991-2013. Seasonal results of the Secchi disc measurements (spring, summer) for 706 lakes were gathered. This is more than 68% of the total number of Polish lakes with a surface area larger than 50 ha. The mean water transparency of these lakes was 1.87 m, while the median was 1.58 m. Distinct inter-regional differences of the Secchi disc transparency were found, and it was also possible to distinguish three relatively homogeneous groups of macroregions where lakes have different optical characteristics. They can be divided into areas with lakes with high (3.05 m), medium (1.99-2.11 m) and low (1.22-1.52 m) water transparency. The Secchi disc transparency of these lakes was also analysed in relation to concentration values of the main forms of the optically significant constituents of water (coloured dissolved organic matter, suspended matter). The mean transparency of turbid, stained and clear lakes was, respectively, 1.16, 2.02, and 2.92 m. Moreover, regional empirical models to predict Secchi disc transparency from chlorophyll a concentration were also developed. It was assumed that inter-regional differences between models could be due to the probably different time of the ice sheet recession. The influence of the lake morphometry was most fully reflected in the impact of the depth conditions.