Volume XV |

Effect of changes in groundwater levels on selected wetland plant communities

Abstract: Wetland areas maintain a high level of moisture at all times and experience flooding at regular intervals. High groundwater levels help create wetland areas, as does a relative lack of surface water loss. The paper bases on the hypothesis that wetland areas are characterized by seasonally high water levels and drought. These changes in water content markedly affect the presence of rare plant communities. The purpose of this paper is to determine the effect of changes in the level of groundwater on selected plant communities in wetland areas. The paper also aims to determine if any other determinants affect these plant communities: (1) relief, (2) climate conditions (precipitation, temperature), (3) human impact. Furthermore, the paper provides a detailed hydrographic analysis of wetland areas including information on water migration pathways, water recharge systems, and sources of water loss. The study area consists of Piaśnickie Łąki – a protected natural area in northern Poland, close to the Baltic coastline. It is also a designated “Nature 2000” area, and it is abundant in rare plant communities such as reed grass (Molinietum medioeuropaeum), which thrives in variable moisture areas. The majority of the research work consisted of literature analysis and fieldwork, which included the installation of a groundwater monitoring system, groundwater and surface water level gauging, and discharge gauging for larger streams found adjacent to the study area. The fieldwork was done in the period 2014 – 2015. The collected research data indicate that groundwater levels did vary during the study period. These conditions helped produce a high rate of plant growth and an increased rate of evapotranspiration across the surface of the study area, which then helped decrease the level of groundwater. One basic condition for the functioning of variable-moisture reed grass communities (Molinietum medioeuropaeum) is a specific pattern of variability in groundwater levels. Small depressions in the studied nature reserve offer the best conditions for the occurrence of reed grass communities.

Volume XV |

Pollution load released into the Bay of Gdańsk by small river catchments in the coastal city of Sopot

Abstract: The purpose of the study is to determine the quantity of wastewater entering the Gulf of Gdańsk, which is part of the Baltic Sea. The study area consists of small river catchments in the city of Sopot, which lies along the Gulf. The research also aims to determine wastewater release volumes over time, instead of focusing only on spatial distributions. Another aim is to identify main determinants potentially affecting water quality in rivers flowing across the city of Sopot. Land use is also considered as a factor. The study area consists of seven small river catchments in the city of Sopot, each with an open flow channel. The study period was 2014 – 2015. Laboratory tests were performed to determine the concentration of both total nitrogen and total phosphorus. Other metrics in the study included pH, specific conductivity, water temperature, dissolved oxygen content, and suspended matter content. Discharge was also measured for each studied river. Comparisons were then made with local meteorological data. Research has shown that none of the 6 studied rivers experienced concentrations of total nitrogen above the norm accepted in Poland for Class 1 water quality (5 mg·dm-3). Mean annual values ranged from 0.60 to 1.28 mg·dm-3. The Class 1 norm for phosphorus (0.2 mg·dm-3) was also not exceeded in the case of total phosphorus in any of the 6 studied rivers. Phosphorus values ranged from 0.066 to 0.1 mg·dm-3. The annual load supplied by all 6 rivers in the Sopot city area during the study period was 4,295.9 kg for total nitrogen and 370.2 kg for total phosphorus. For the purpose of comparison, the load supplied by Poland as a whole in the year 2012 was: 210,768,000 kg total nitrogen, and 15,269,000 kg total phosphorus. In summary, the 6 small rivers discussed in this paper contribute 0.002% of the biogenic load supplied to the Baltic Sea by Poland as a whole.