Features of the species composition and structure of fish communities in small anthropogenic reservoirs with different content of dissolved mineral nitrogen

In 22 small anthropogenic reservoirs with an area of 0.4 to 62 ha located in the territory of the Udmurt Republic, individuals of different fish species were captured and water samples were taken in late spring for analysis of NO3–, NO2– and NH4+ content. In many reservoirs, concentrations of ammonium exceed the maximum permissible according to the fishing standards for water quality, and in some this is also the case with nitrites. Ponds with zooplanktophages (bleak Alburnus alburnus (L.) and belica Leucaspius delineates (Heckel)) present in fish communities were statistically significantly different in the increased content of total dissolved mineral nitrogen from reservoirs where these two fish species were not registered. In perch and roach reservoirs, the numerical proportion of river perch Perca fluviatilis was negatively and statistically significantly related to the level of their contamination with nitrogen ionic forms.

Monitoring of the ecological state of the city lake of Chita

Introduction. The paper presents the results of the studies on assessing the quality of the aquatic ecosystem of a lake located within the city. The European perch (Perca fluviatilis L.) and the Gibel carp (Carassius gibelio) were used as an indicator for determining the quality of the aquatic ecosystem by the method of fluctuating asymmetry. Problem Statement. The aim of the work was to conduct monitoring with the subsequent assessment of the quality of the ecosystem of the city lake using the method of fluctuating asymmetry (hereinafter FA). Theoretical and Practical Part. The quality of the urban lake aquatic ecosystem was assessed using the FA method (indicators: the European perch (Perca fluviatilis L.), 1758 and the Gibel carp (Carassius auratus Bloch), 1783). To identify the reasons for the high PFA values, a chemical analysis (in an accredited laboratory) of the gills of the Gibel carp for heavy metals was performed. Conclusions. As a result of the research, the FA indicators values for these indicators were obtained. According to the results of a laboratory study of the content of heavy metals in the gill arches of the Gibel carp, an excess of the maximum permissible concentration of 8 out of 10 analyzed elements was revealed. It has been established that the ecosystem of the city lake Kenon is experiencing a significant anthropogenic load (5 points — the critical quality of the aquatic environment) and it continues to increase towards the deterioration of the habitat.

Trophic Interactions Promoting Dominance by Cyanobacteria in a Freshwater Pelagic Food Web

<p>Cyanobacterial blooms have occurred in the Lower Karori Reservoir (Wellington) for approximately the last eight years. The dominant species in the past have been identified as Anabaena lemmermannii and A. circinalis. The reservoir was built in 1874 as part of the first water supply scheme for Wellington City and has been closed to the public since 1906. The catchment was created into a "predator-free" native wildlife sanctuary in 1999. The first severe bloom in the Lower Karori Reservoir occurred during the summer of 2000/01. The objectives of this study were: - To establish a baseline knowledge of the food web within the Lower Karori Reservoir. - To follow the chemical and biological dynamics of the Lower Karori Reservoir for an extended period of time to observe seasonal changes associated with the cyanobacterial blooms. - To experimentally manipulate the trophic levels of the food web to determine which factors (i.e. resources or consumers) were most significant in promoting the growth of cyanobacteria. I sampled temperature, dissolved oxygen, nutrient levels, and phytoplankton and zooplankton communities from 7 October 2003 to 7 July 2004. I also monitored the diet of the zooplanktivorous fish (perch, Perca fluviatilis) present in the lake. The dominant cyanobacteria species was found to be A. lemmermannii. Three other cyanobacteria species were present during the study at low abundances, including A. planktonica which had not been previously recorded in the reservoir. The bloom of cyanobacteria was associated with thermal stratification. Nutrient concentrations were at moderate levels, characteristic of mesotrophic lakes. The perch population consisted mostly of smallsized individuals that feed predominately on large species of zooplankton that were at low abundances within the lake. During March 2004, I conducted a food web manipulation experiment within the Lower Karori Reservoir. I sought to test the role of nutrient resources (bottom-up) versus cascading effects of zooplanktivorous perch (Perca fluviatilis) (top-down) in controlling cyanobacteria in this lake. Experimental treatments with perch had higher levels of cyanobacterial densities, lower zooplankton species diversity and zooplankton species were generally smaller-sized than in treatments without perch. Nutrient treatments were not favourable for cyanobacteria as the addition of nitrogen probably meant that nitrogen fixing Anabaena species lost competitive advantage over other phytoplankton taxa. It is not known by which mechanism perch promoted cyanobacterial growth since this was not directly measured. Plankton community composition was altered by all treatments. This study indicates that blooms of Anabaena species in the Lower Karori Reservoir are the result of a number of complex interactions within the lake food web. Low nitrogen levels favour dominance by the nitrogen fixing cyanobacteria, which bloom during thermal stratification as they are able to maintain their position in the water column due to buoyancy control. Predation pressure by perch is likely keeping large filter-feeding zooplankton at low levels and thus reducing grazing pressure on phytoplankton. Phosphorus excretion by perch also probably favours cyanobacteria. An eradication of perch within the Lower Karori Reservoir would probably contribute to prevent cyanobacteria predominance. The removal of perch from the reservoir should be reasonably simple due its small size and contained area. Other methods which may help reduce cyanobacterial blooms within the reservoir include artificial mixing to prevent stratification. However, these methods can be expensive to install and run.</p>

Trophic Interactions Promoting Dominance by Cyanobacteria in a Freshwater Pelagic Food Web

<p>Cyanobacterial blooms have occurred in the Lower Karori Reservoir (Wellington) for approximately the last eight years. The dominant species in the past have been identified as Anabaena lemmermannii and A. circinalis. The reservoir was built in 1874 as part of the first water supply scheme for Wellington City and has been closed to the public since 1906. The catchment was created into a "predator-free" native wildlife sanctuary in 1999. The first severe bloom in the Lower Karori Reservoir occurred during the summer of 2000/01. The objectives of this study were: - To establish a baseline knowledge of the food web within the Lower Karori Reservoir. - To follow the chemical and biological dynamics of the Lower Karori Reservoir for an extended period of time to observe seasonal changes associated with the cyanobacterial blooms. - To experimentally manipulate the trophic levels of the food web to determine which factors (i.e. resources or consumers) were most significant in promoting the growth of cyanobacteria. I sampled temperature, dissolved oxygen, nutrient levels, and phytoplankton and zooplankton communities from 7 October 2003 to 7 July 2004. I also monitored the diet of the zooplanktivorous fish (perch, Perca fluviatilis) present in the lake. The dominant cyanobacteria species was found to be A. lemmermannii. Three other cyanobacteria species were present during the study at low abundances, including A. planktonica which had not been previously recorded in the reservoir. The bloom of cyanobacteria was associated with thermal stratification. Nutrient concentrations were at moderate levels, characteristic of mesotrophic lakes. The perch population consisted mostly of smallsized individuals that feed predominately on large species of zooplankton that were at low abundances within the lake. During March 2004, I conducted a food web manipulation experiment within the Lower Karori Reservoir. I sought to test the role of nutrient resources (bottom-up) versus cascading effects of zooplanktivorous perch (Perca fluviatilis) (top-down) in controlling cyanobacteria in this lake. Experimental treatments with perch had higher levels of cyanobacterial densities, lower zooplankton species diversity and zooplankton species were generally smaller-sized than in treatments without perch. Nutrient treatments were not favourable for cyanobacteria as the addition of nitrogen probably meant that nitrogen fixing Anabaena species lost competitive advantage over other phytoplankton taxa. It is not known by which mechanism perch promoted cyanobacterial growth since this was not directly measured. Plankton community composition was altered by all treatments. This study indicates that blooms of Anabaena species in the Lower Karori Reservoir are the result of a number of complex interactions within the lake food web. Low nitrogen levels favour dominance by the nitrogen fixing cyanobacteria, which bloom during thermal stratification as they are able to maintain their position in the water column due to buoyancy control. Predation pressure by perch is likely keeping large filter-feeding zooplankton at low levels and thus reducing grazing pressure on phytoplankton. Phosphorus excretion by perch also probably favours cyanobacteria. An eradication of perch within the Lower Karori Reservoir would probably contribute to prevent cyanobacteria predominance. The removal of perch from the reservoir should be reasonably simple due its small size and contained area. Other methods which may help reduce cyanobacterial blooms within the reservoir include artificial mixing to prevent stratification. However, these methods can be expensive to install and run.</p>

Effects of Garlic Allium sativum Powder on Nutrient Digestibility, Haematology, and Immune and Stress Responses in Eurasian Perch Perca fluviatilis Juveniles

The supplementation of fish diets with phytogenics can increase growth performance and can modulate immune system response. European perch Perca fluviatilis (initial weight 25.0 ± 0.4 g) were fed a diet including 0 (Control), 10 (G10), 20 (G20), and 30 (G30) g kg−1 garlic powder. No significant difference in the growth parameters and somatic indices were observed. Significantly higher fat digestibility was observed in G10 and G30 diets compared to in the control and G20 diets(p < 0.05). Significantly greater red blood cell and white blood cell counts were observed with the G10 diet (p < 0.05). Garlic significantly decreased serum cholesterol in all of the experimental groups. Serum albumin was significantly higher in the G10 and G20 diets (p < 0.05). Immediately after the overcrowding stress challenge, the garlic groups showed significantly higher cortisol levels than the control group, while no significant difference was observed in the glucose concentration among groups. At 1 h post-stress, all of the groups that had been fed a garlic-supplemented diet showed lower cortisol levels than the control group, and this trend was maintained at 6 and 24 h post stress (p < 0.05), and glucose level in all garlic groups was significantly lower than control (p < 0.05). Garlic at 10 g kg−1 in feed can improve apparent fat digestibility and selected blood parameters and can enhance resistance against high-density and net handling stress in Eurasian perch.