Anthropogenic pollution leads to increased concentrations of metals in the freshwater and macrophyte. Aquatic plants substantially contribute to the structure, function as well as and service provision of aquatic ecosystems. Our microcosm experiments were to test the possibility of the physiological response of Hydrocharis morsus-ranae to metal (Cd, Pb, Cu, Zn, Mn, Fe at three level of concentration) contaminated waters. Biomass was analysed at the beginning and at the end of the experiment. At the same time contents of photosynthetic pigments in leaves were estimated spectrophotometrically. We found that this macrophyte had the ability to grow in contaminated waters, but the effects of high concentration of isolated metals in water will indicate changes consisting in the disappearance of a significant part of biological populations were which manifested in alteration of the content of photosynthetic pigments as well as this plant’s growth. We show that generally stress of Zn and Cu influenced the drop of dry biomass which was connected with a positive correlation between the amount of dry biomass and the content of chlorophyll a and carotenoids, or only carotenoids, respectively. The highest stress of Pb and Fe (third concentrations of these metals) also influenced the drop of biomass. We concluded that none of Cd concentrations were toxic to this plant, but the effect of Mn stress was not unequivocal. Moreover, plant growth was stimulated by low Fe concentrations (first concentration) demonstrating the hormesis effect. When plants were exposed to this metal, there was no evidence of damage to the photosynthetic processes.

The pot experiment was conducted to access the soil microorganisms biomass (physiological method – Substrate Induced Respiration) and emissions of N2O, CO2 and CH4 (photoacoustic infrared detection method), and grasses biomass (weight method). The obtained results of analysed gases were converted to CO2 equivalent. There was no effect of the microorganisms biomass on the N2O emissions. The increase in CO2 emissions was accompanied by an increase in the microorganisms biomass (r = 0.48) under the conditions of the I swath and acid soil reaction, as well as the II swath and neutral reaction ( r = 0.94). On the other hand, in the case of CH4 emission, such a relationship was noted both swaths under the conditions of neutral reaction ( r = 0.51), but a negative correlation ( r = –0.71) was noted for the acid reaction only at the II swath. The increase in the grasses biomass with the increase in the microorganisms biomass was recorded only at the II swath in neutral reaction ( r = 0.91). In a short period of time, with the neutral soil reaction with the increase in the soil microorganisms biomass, an increase in CO2 sequestration and biomass of cultivated grasses was noted. Information on the determination of the microorganisms groups responsible mainly for the transformation of carbon compounds and CO2 and CH4 emissions from the soils of grasslands would be valuable scientifically.

The paper discusses the current prognoses of aquaculture development worldwide putting an emphasis on its effect on the environment and the issue of the protection of water reservoirs in different countries. Water consumption in diversified aquaculture systems is presented herein as well as the characteristics of the mechanical and biological water treatment methods in fish farms, with particular attention paid to the recirculating water systems. New aquaculture technologies using post-production waters are presented. The paper provides a discussion on the contribution of aquaculture to the global greenhouse gas emissions and the means of limiting this emission. The effect of climate change on aquatic ecosystems is presented in the context of the changes of the aquaculture production profile. The paper includes a brief presentation of the methods of mitigating the changes with respect to contamination of aquatic ecosystems as well as climate change. Reducing the water footprint can be achieved through selective breeding, species diversification and implementation of more technologically advanced aquaculture systems such as: integrated multi-trophic aquaculture, aquaponics and recirculation systems in aquaculture. The need for certification of fish farms with water recirculation systems is justified in the paper. The issues addressed herein are summarised and the main areas for extending the research promoting preservation of aquatic ecosystems in aquaculture are presented.