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Nutrients from beach recreation in the context of the limnological status of a mesotrophic lake

100%

Serafin A. , Grzywna A. , Augustyniak R. , Bronowicka-Mielniczuk U.

tom no. 54

160--171

The study objective was to analyse the number of tourists present in the shore zone and bathing areas of lakes with regard to their tourist carrying capacity and the amount of biogenic substances potentially entering the ecosystem from the beach and bathing areas. The procedures from project between the EU and Poland, in the module “Development of the sanitary supervision of water quality” were used in three categories: physiological substances - sweat and urine; water-soluble and insoluble organic compounds; and biogenic elements - nitrogen and phosphorus. The research was conducted in two model mesotrophic lakes, Piaseczno and Zagłębocze, located in the Łęczna-Włodawa Lakeland (eastern Poland). The data were analysed in reference to biological trophic status indices defining the limnological status of lakes in the summer of 2014 and 2016. Analyses of gross primary production of phytoplankton using the light and dark bottles method and the analysis of chlorophyll a concentration were applied using the laboratory spectrophotometric method. The relatively small number of tourists recorded in the shore zone of both lakes did not exceed their tourist carrying capacity, and their potential contribution of biogenic substances to the lake ecosystems was small. Biological trophic indices for both lakes indicated that they had been continually late-mesotrophic for decades. The amount of biogenic substances directly linked to beach tourism usually has a minor effect on the limnological status of mesotrophic lakes. Due to the specific character of lake ecosystems, however, even small amounts of these substances can contribute to the destabilisation of the biocenotic system.

The suitability of zooplankton as lake ecosystem indicator; Crustacean trophic state index

100%

Ejsmont-Karabin J. , Karabin A.

tom Vol. 61, nr 3

561--573

Industrial processes and the use of fertilizers are the main causes for the rapid eutrophication of lakes. Different indices, both chemical and biological, may be used to assess a level and a rate of the eutrophication process. Zooplankton indices can be among them, as zoo plankton community structure is determined primarily by the physical and chemical environment and modified by biological interactions, i.e. predation and interspecific competition for food resources. Among biological indices of trophic state of lake, those based on densities and structure of crustacean communities seem to respond weaker. There are, however, patterns of crustacean com munities connected with trophic state of lakes. Thus, an increase in trophic state causes: (1) an increase in the total numbers of crustaceans; (2) an increase in the total biomass of Cyclopoida; (3) an increase in the contribution of the biomass of Cyclopidae to the total crustacean biomass; (4) an increase in the ratio of the biomass of Cyclopoida to the biomass of Cladocera; (5) a decrease in the average body weight of Crustacea; (6) an increase in the ratio of Cladocera to Calanoida numbers; (7) an increase in the ratio of Cyclopoida to Calanoida numbers; (8) an increase in the dominance of species indicative of high trophy (Mesocyclops leuckartii, Thermocyclops oithonoides, Diaphano soma brachyurum, Chydorus sphaericus, Bosmina (Eubosmina) coregoni thersites) in the numbers of all indicative species. Crustacean zooplankton was sampled at the deepest place in a lake at 1 m intervals from the surface to the bottom of epilimnion layer, and then samples were pooled together for the layer. Samples were taken once a year, during the summer stagnation. The material was collected from a total of 41 dimictic and 33 polymictic lakes within Masurian Lake District, Iława Lake District and Lubawa Upland. Among above-mentioned indices, six were the best correlated with trophic state of lakes. Below are formulas which enable to assess trophic state of lakes regardless of their mixis type (TSICR) from parameters of abundance and structure of crustacean communities: (1) TSICR1 = 25.5 N0.142 (R2 = 0.32), where TSI = trophic state index; N = numbers (ind. 1-1); (2) TSICR2 = 57.6 B0.081 (R2 = 0.37), where B = biomass (mg w.wt. 1-1); (3) TSICR3 = 40.9 CB0.097 (R2 = 0.35), where CB = percentage of biomass of Cyclopoida in the total biomass of Crustacea (%); (4) TSICR4 = 58.3 (CY/CL)0.071 (R2 = 0.30), where CY/CL = ratio of the Cyclopoida biomass to the biomass of Cladocera (%); (5) TSICR5 = 5.08 Ln (CY/CA) + 46.6 (R2 = 0.37), where CY/CA = ratio of Cyclopoida numbers to the numbers of Calanoida; (the relationship covering exclusively dimictic lakes); (6) TSICR5 = 43.8 e0.004 (IHT) (R2 = 0.30), where IHT = percentage of species indicative of high trophy in the indicative group’s numbers. It was assumed that the lakes with a TSICR under 45 are mesotrophic, those with a TSICR value of 45–55 are meso-eutro phic, those with a TSICR value of 55–65 – eutrophic and those with a TSICR above 65 – hypertrophic. Al though crustacean indices of trophic state of lakes seem to be less useful than other biological indices, they may be recommended in assessing the quality of lake waters.