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Respiration and oxygen deficit risk in eutrophic fishponds
LENDLEROVÁ, Lucie
The purpose of this thesis is to obtain informations about the parameters of environment, which increases respiratory processes in fishponds and can cause an oxygen deficit. 24 monitored lakes were chosen according to the requirements of Rybářství Třeboň a.s. Between 4. 2. 2014 and 30. 9. 2014 took place 10 samplings. Water samples were taken for chemical laboratory analysis. At the same time there were made field measurements of basic physico-chemical parameters - dissolved oxygen concentration, temperature, color and transparency. Laboratory analysis determined compound and forms of nitrogen, phosphorus, carbon and the quantity of chlorophyll-a. Plankton respiration per 24 hours was detected by measuring the oxygen consumption by plankton in sizes up to 235 microns. Relations between respiration and other parameters, and different concentration of dissolved oxygen at the surface and in the depth of 1 m and the other parameters were compared using regression and correlation analysis. The observed decreasing trend of the seasonal oxygen saturation indicates that whole fishpond is dominated by respiratory processes. The results of correlation analysis, comparing the relationship of environmental parameters and respiration pelagial per 24 hours, shows that respiration correlates most with organic carbon content (representing the amount of organic substance). Furthermore, positively correlates content of total nitrogen, the amount of phytoplankton expressed as chlorophyll-a concentration and transparency. Content of particulate and total nitrogen, amount of phytoplankton and transparency also positively correlated with respiration. Total phosphorus concentration correlates with the respiration least of the monitored parameters.
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Fish excretion of ammonia under different oxygen environmental conditions
MÜLLEROVÁ, Lucie
The aim of this work was to find out and compare amount of ammonia nitrogen excreted by fish in different oxygen saturation of water. Experiments (preliminary, main and additional) were made with ornamental form of common carp (Cyprinus carpio f. Koi) at Laboratory of Aquatic Toxicology and Ichtyopathology RIFCH in Vodňany. The preliminary (orientation) experiment was made in three different dissolved oxygen concentrations (I. 0,65 - 2,66; II. 2,43 - 5,70; III. 6,40 - 6,50 mg.l-1 O2) and fish production of ammonia nitrogen after 2 hours was I. 24,61; II. 85,29; III. 70,19 mg N-NH4+ per 1 kg of fish weight. The fish were also exposed to different oxygen conditions (hypoxia0,76 - 1,46; normoxia 9,8 - 9,46 mg.l-1 O2) in the main experiment which was repeated six times. Detected production of ammonia nitrogen in recalculated to 1 kg fish weight was 25,01 +- 3,14 mg N-NH4+ by the fish in hypoxia and 32,56 +- 4,08 mg N-NH4+ by the fish in normoxia after two hours of experiment duration. Detected difference was statistically significant (P < 0,05). Haematology and biochemical blood examination of fish which were exposed to hypoxia proved statistically significant increasing number of leukocytes, value of haematocrit, concentration of ammonia and glucose was made in the end of experiment. The additional experiment was repeated five times, the fish were exposed to hypoxia there (0,99 - 1,21 mg.l-1 O2) and the control fish were kept in water with concentration of dissolved oxygen between 7,67 - 9,11 mg.l-1. Statistically significant differences in ammonia nitrogen production were already found out in these groups of fish after two hours of experiment duration and difference increased markedly after 4,5 hours (fish production of ammonia exposed to hypoxia 47,92 +- 4,91 mg.kg-1 and in the control fish 101,53 +- 8,31 mg.kg-1). Production of ammonia by the fish originally exposed to hypoxia almost aligned to production of control fish during 2,5 hours after an aeration had been added to the fish in hypoxia. Production of ammonia nitrogen was 93,38 +- 17,82 mg.kg-1 by the fish originally exposed to hypoxia and 110,13 +- 18,21 mg.kg-1 by the control fish. This difference was not statistically significant yet. The results of experiment proved that fish ability to excrete ammonia from body is closely connected with oxygen conditions in water environment.
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