The effect of the anaesthetics 1 Clove oil and MS-222 on the sedation, recovery, survival, population growth and fecundity of the calanoid copepod, Pseudodiaptomus hessei Copepoda Calanoida under culture conditions.
- Authors: Bulube, Masivuye Nomazizi
- Date: 2023-01
- Subjects: Water quality , Marine biodiversity , Aquatic animals -- Food
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/27524 , vital:67430
- Description: Compared to current live food organisms used in aquaculture, the calanoid copepod, Pseudodiaptomus hessei is smaller and has a superior nutritional value. However, due to their fast and erratic movements, manipulating and counting this species for aquaculture research purposes is difficult. For easier manipulation it is therefore necessary to sedate the copepods. The study aimed to determine the effect of two anaesthetics on sedation, recovery, survival, population growth and fecundity of the calanoid copepod, Pseudodiaptomus hessei, under culture conditions. Male and female P. hessei were exposed to the anaesthetics clove oil and Tricaine Methane sulfonate (MS-222). Twelve replicates of five copepods each were exposedto clove oil at 100, 150 and 200 μL/L, and to MS-222 at 300, 600, 900, 1200 and 1500 mg/Lwith the number of fully sedated copepods being recorded. clove oil sedation only occurredafter 5:23±1:25 minutes in the 100 μL/L treatment while copepods exposed to 150 and200μL/L were anaesthetized within 2:48±0:46 and 0:40±0:07 minutes respectively. Sedation did not occur in MS-222 at concentrations of 300 and 600 mg/L while at 900 mg/L all copepodswere sedated within 4:19±0:41 minutes. Only copepods exposed to 1200 and 1500 mg/L were all fully sedated within 2:26±1:46 and 1:23±0:37 minutes respectively. Clove oil recovery onlyoccurred at 4:40±1:32 minutes in the 100 μL/L treatment while copepods exposed to 150 and200 μL/L recovered at 8:30±1:46 and 12:12±0:59 minutes, respectively. In this study, all MS- 222 treatments showed full recovery at 1:07±0:41 to 1:11±0:41 minutes with 100% survivalrate. The growth development FPN (Final Population Number) for Clove oil, MS-222 and control were not different from the control indicating that exposure to the anaesthetic had no effect on their long-term survival (21 days). The mean clutch size of 34±5 eggs per sac was high compared to other studies on the species. Based on these findings the 150 μL/L Clove oiland 1200 mg/L MS-222 concentrations were the lowest doses of each anaesthetic to induce full sedation within 3 minutes followed by rapid recovery 87 within three minutes without it affecting its short (24 hours) and long-term survival, population growth and fecundity. Basedon sedation and recovery rates, effect on survival, fecundity and growth as well as cost and ease use, the 1200 mg/L MS-222 concentration is the recommended to safely anaesthetize P. hessei. , Thesis (MSci) -- Faculty of Science and Agriculture, 2023
- Full Text:
- Date Issued: 2023-01
- Authors: Bulube, Masivuye Nomazizi
- Date: 2023-01
- Subjects: Water quality , Marine biodiversity , Aquatic animals -- Food
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/27524 , vital:67430
- Description: Compared to current live food organisms used in aquaculture, the calanoid copepod, Pseudodiaptomus hessei is smaller and has a superior nutritional value. However, due to their fast and erratic movements, manipulating and counting this species for aquaculture research purposes is difficult. For easier manipulation it is therefore necessary to sedate the copepods. The study aimed to determine the effect of two anaesthetics on sedation, recovery, survival, population growth and fecundity of the calanoid copepod, Pseudodiaptomus hessei, under culture conditions. Male and female P. hessei were exposed to the anaesthetics clove oil and Tricaine Methane sulfonate (MS-222). Twelve replicates of five copepods each were exposedto clove oil at 100, 150 and 200 μL/L, and to MS-222 at 300, 600, 900, 1200 and 1500 mg/Lwith the number of fully sedated copepods being recorded. clove oil sedation only occurredafter 5:23±1:25 minutes in the 100 μL/L treatment while copepods exposed to 150 and200μL/L were anaesthetized within 2:48±0:46 and 0:40±0:07 minutes respectively. Sedation did not occur in MS-222 at concentrations of 300 and 600 mg/L while at 900 mg/L all copepodswere sedated within 4:19±0:41 minutes. Only copepods exposed to 1200 and 1500 mg/L were all fully sedated within 2:26±1:46 and 1:23±0:37 minutes respectively. Clove oil recovery onlyoccurred at 4:40±1:32 minutes in the 100 μL/L treatment while copepods exposed to 150 and200 μL/L recovered at 8:30±1:46 and 12:12±0:59 minutes, respectively. In this study, all MS- 222 treatments showed full recovery at 1:07±0:41 to 1:11±0:41 minutes with 100% survivalrate. The growth development FPN (Final Population Number) for Clove oil, MS-222 and control were not different from the control indicating that exposure to the anaesthetic had no effect on their long-term survival (21 days). The mean clutch size of 34±5 eggs per sac was high compared to other studies on the species. Based on these findings the 150 μL/L Clove oiland 1200 mg/L MS-222 concentrations were the lowest doses of each anaesthetic to induce full sedation within 3 minutes followed by rapid recovery 87 within three minutes without it affecting its short (24 hours) and long-term survival, population growth and fecundity. Basedon sedation and recovery rates, effect on survival, fecundity and growth as well as cost and ease use, the 1200 mg/L MS-222 concentration is the recommended to safely anaesthetize P. hessei. , Thesis (MSci) -- Faculty of Science and Agriculture, 2023
- Full Text:
- Date Issued: 2023-01
Spatial assessment of riparian vegetation condition in relation to water quality: a case of the Keiskamma River, Eastern Cape Province, South Africa
- Authors: Teyise, Anda
- Date: 2022-11
- Subjects: Water quality , Riparian plants , Stream health
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/27679 , vital:69393
- Description: Riparian vegetation plays several roles in ecological functioning, such as improving water quality because it can filtrate the sediments and provides stability on the floodplain. The condition of riparian vegetation can serve to provide information regarding river condition. The main purpose of this study was to investigate the extent to which water quality level of the Keiskamma River can be explained by the riparian vegetation density patterns. This study used Sentinel-2 Multi-Spectral Instrument (MSI) satellite image to assess spatial patterns in riparian vegetation condition. The Normalized Difference Vegetation Index (NDVI) was generated from the Sentinel-2 imagery and was used as the base from which riparian vegetation density classes were obtained through the supervised image classification technique. The image classification accuracy assessment was caried out to verify and validate the accuracy of riparian vegetation density classes. This technique produced the overall accuracy (OA) classification of 83.72 percent. The riverine water quality parameters were measured on the randomly surveyed sites using the Premium Series PC60 5-in-1 Water Quality Tester. High density of riparian vegetation were found in the upper course of the river. The low-density riparian vegetation dominates the middle course of the river while the lower part of the river contains a mixture of the three riparian vegetation conditions. The one-sample t-test statistical technique was carried out to determine the spatial pattern of water quality parameters. The t-test results revealed the significant variation in water pH, with the p-value of 0.00. However, t-test results also showed insignificant variations in water Total Dissolved Solids (TDS) and electrical conductivity (EC), with p-values of 0.117 0.059 and 0.059 respectively. The linear regression was used to determine the relationship between riparian vegetation and water quality. In this case, the NDVI values were used as surrogate for riparian vegetation condition. The results showed insignificant relationships between NDVI and water pH (r2 = 0.00), NDVI and water TDS (r2 = 0.09), and NDVI and water EC (r2 = 0.09) along the Keiskamma River. In view of the findings obtained from this study “spatial differences in riparian vegetation along the lateral and longitudinal dimensions of the Keiskamma River denote spatial variations in water quality levels”, is rejected. , Thesis (MSci) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Date Issued: 2022-11
- Authors: Teyise, Anda
- Date: 2022-11
- Subjects: Water quality , Riparian plants , Stream health
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/27679 , vital:69393
- Description: Riparian vegetation plays several roles in ecological functioning, such as improving water quality because it can filtrate the sediments and provides stability on the floodplain. The condition of riparian vegetation can serve to provide information regarding river condition. The main purpose of this study was to investigate the extent to which water quality level of the Keiskamma River can be explained by the riparian vegetation density patterns. This study used Sentinel-2 Multi-Spectral Instrument (MSI) satellite image to assess spatial patterns in riparian vegetation condition. The Normalized Difference Vegetation Index (NDVI) was generated from the Sentinel-2 imagery and was used as the base from which riparian vegetation density classes were obtained through the supervised image classification technique. The image classification accuracy assessment was caried out to verify and validate the accuracy of riparian vegetation density classes. This technique produced the overall accuracy (OA) classification of 83.72 percent. The riverine water quality parameters were measured on the randomly surveyed sites using the Premium Series PC60 5-in-1 Water Quality Tester. High density of riparian vegetation were found in the upper course of the river. The low-density riparian vegetation dominates the middle course of the river while the lower part of the river contains a mixture of the three riparian vegetation conditions. The one-sample t-test statistical technique was carried out to determine the spatial pattern of water quality parameters. The t-test results revealed the significant variation in water pH, with the p-value of 0.00. However, t-test results also showed insignificant variations in water Total Dissolved Solids (TDS) and electrical conductivity (EC), with p-values of 0.117 0.059 and 0.059 respectively. The linear regression was used to determine the relationship between riparian vegetation and water quality. In this case, the NDVI values were used as surrogate for riparian vegetation condition. The results showed insignificant relationships between NDVI and water pH (r2 = 0.00), NDVI and water TDS (r2 = 0.09), and NDVI and water EC (r2 = 0.09) along the Keiskamma River. In view of the findings obtained from this study “spatial differences in riparian vegetation along the lateral and longitudinal dimensions of the Keiskamma River denote spatial variations in water quality levels”, is rejected. , Thesis (MSci) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Date Issued: 2022-11
Assessment of the water quality, incidence of enteric viruses and microbial risk in the Buffalo River in the Eastern Cape Province of South Africa
- Chigor, Vincent Nnamdigadi https://orcid.org/0000-0002-0811-4526
- Authors: Chigor, Vincent Nnamdigadi https://orcid.org/0000-0002-0811-4526
- Date: 2013-03
- Subjects: Water quality , Water -- Microbiology
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24272 , vital:62596
- Description: Buffalo River is an important water resource in the Eastern Cape Province of South Africa. Over a 1-year period (August 2010–July 2011), the water quality and incidence of human enteric viruses (HEntVs) was assessed, using standard methods and molecular techniques and a total 72 composite water samples collected monthly from a total of 6 sites located on the river and three dams along its course. The sites were selected based on a number of factors including geographical location, anthropogenic activity/major water use, rural/urban status and access. A total of 13 physicochemical parameters were determined using the standard methods. The counts of faecal indicator bacteria (FIB) including total coliforms (TC), faecal coliforms (FC) and enterococci (ENT) were determined by the membrane filtration technique. HEntVs were concentrated using an adsorption-elution method based on cation (Al3+)-coated membrane filter. Real-time quantitative polymerase chain reaction (qPCR) was used for the detection and quantification of human adenoviruses (HAdV), and real-time reverse transcriptase-PCR (RT-qPCR) was used for the quantitative detection of hepatitis A virus (HAV), human rotaviruses (RoV) and enteroviruses (EnV). The detected HAdV were characterized by multiplex conventional/semi-nested PCR methods. The risks for human health constituted by exposure to the detected HEntVs at the six sites were evaluated by a static quantitative microbial risk assessment (QMRA) using both the exponential and beta-Poisson models. Water temperature ranged from 11 to 28oC, while pH varied from 6.6 to 10.7, and turbidity from 1.7 to 133 NTU. Electrical conductivity (EC), total dissolved solids (TDS) and salinity showed drastic variations (42.3-46693 μS/cm, 20.3–23350 mg/L and 0.02–33.8 PSU respectively). The concentrations of other parameters ranged as follows: chloride (3.7–168 mg/L); DO (6.9–11.1); BOD (0.6–9.4); COD (3.7–45.9); nitrite-nitrogen (0.02–0.21); nitrate-nitrogen (1–4.47); and orthophosphate (0.01–1.72). TC, FC and ENT counts were high and ranged from 1.9 × 102–3.8 × 107 cfu/100 mL, 0–3.0×105 cfu/100 mL and 0–5.3 × 105 cfu/100 mL for TC, FC and ENT respectively. Significantly (P<0.05) higher concentrations of FC and ENT were observed at the sampling sites located at the lower reaches of the river compared to the upper reaches. The FIB counts mostly exceeded the maximum limits recommended by national and international guidelines for safe fresh produce irrigation, domestic applications, full-contact recreation and livestock watering. Significant (P<0.01) positive correlations existed between TDS and salinity (r=0.921), between turbidity and each of TC (r=0.552) and FC (r=0.425), as well as between BOD and each of TC (r=0.282), FC (r=0.472) and ENT (r=0.552). Phosphate correlated positively with FC (r=0.424), and nitrate also with the same, FC (r=0.460). A strong positive correlation existed between FC and ENT (r=0.915). There existed a significant (P˂0.01) inverse correlation between enteric viruses and each of water temperature (r=-0.191) and pH (r=-0.234). No correlation could be deduced between enteric viruses and all the tested chemical and bacteriological parameters. HAV, HAdV, RoV and EnV were detected in 43.1percent, 34.7percent, 13.9percent and 9.7percent respectively of the total 72 water samples tested. Two or more viruses were detected in 22.2 percent of the samples. HAdV were detected at 5 of the 6 sampling sites with concentrations ranging from 1.2×101 genome copies (GC)/litre to 4.71×103 GC/litre. Epidemiologically important serotypes, Ad40/41 constituted 83.3percent, while Ad21 made up 16.7percent of all the HAdV detected. HAV was detected at all the sites in significantly (p < 0.05) varying concentrations that ranged from 1.5 × 101–1.9 × 105 GC/litre compared to RoV and EnV. Neither of RoV nor EnV was detected at any of the dams. The detected concentrations at the non-dam sites ranged from 2.5 × 101–2.1 × 103 GC/litre and 1.3 × 101–8.6 × 101 GC/litre for RoV and EnV respectively. The values for the estimated daily risks of enteric virus infection varied with sites and exposure scenario, and ranged from 7.31×10-3–1 (for HAdV), 4.23×10-2–6.54×10-1 (RoV), 2.32×10-4–1.73×10-1 (HAV) and 1.32×10-4–5.70×10-2 (EnV). The yearly risks of infection in individuals exposed to the river/dam water via drinking, recreational, domestic or irrigational activities were unacceptably high, exceeding the acceptable yearly risk of 0.01percent (10-4 infection/person/year) recommended by the USEPA for drinking water. The risks of illness and of death from infection ranged from 6.58×10-5–5.0×10-1 and 6.58×10-9–5.0×10-5 respectively. Data on the physicochemical and bacteriological parameters showed that the Buffalo River water quality was poor, and deteriorated in the plains compared to the upper reaches. These water quality data, the presence of enteric viruses and the QMRA data, that revealed unacceptably high risks of enteric virus infections, and of illness and mortality from the infections, show that the Buffalo River and its dams are contaminated waters that constitute significant public health hazards. Provision of adequate sanitary infrastructure will help prevent source water contamination, and public health education aimed at improving personal, household and community hygiene is imperative. Monitoring enteric viruses in rivers and source water dams is necessary and useful as a risk assessment tool for the exposed population. Future research should consider a comprehensive characterization of the detected viruses. This work is both a significant contribution to the molecular epidemiology of enteric viruses and the first report on molecular detection and quantification of enteric viruses in surface waters in the Eastern Cape. , Thesis (PhD) -- Faculty of Science and Agriculture, 2013
- Full Text:
- Date Issued: 2013-03
- Authors: Chigor, Vincent Nnamdigadi https://orcid.org/0000-0002-0811-4526
- Date: 2013-03
- Subjects: Water quality , Water -- Microbiology
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24272 , vital:62596
- Description: Buffalo River is an important water resource in the Eastern Cape Province of South Africa. Over a 1-year period (August 2010–July 2011), the water quality and incidence of human enteric viruses (HEntVs) was assessed, using standard methods and molecular techniques and a total 72 composite water samples collected monthly from a total of 6 sites located on the river and three dams along its course. The sites were selected based on a number of factors including geographical location, anthropogenic activity/major water use, rural/urban status and access. A total of 13 physicochemical parameters were determined using the standard methods. The counts of faecal indicator bacteria (FIB) including total coliforms (TC), faecal coliforms (FC) and enterococci (ENT) were determined by the membrane filtration technique. HEntVs were concentrated using an adsorption-elution method based on cation (Al3+)-coated membrane filter. Real-time quantitative polymerase chain reaction (qPCR) was used for the detection and quantification of human adenoviruses (HAdV), and real-time reverse transcriptase-PCR (RT-qPCR) was used for the quantitative detection of hepatitis A virus (HAV), human rotaviruses (RoV) and enteroviruses (EnV). The detected HAdV were characterized by multiplex conventional/semi-nested PCR methods. The risks for human health constituted by exposure to the detected HEntVs at the six sites were evaluated by a static quantitative microbial risk assessment (QMRA) using both the exponential and beta-Poisson models. Water temperature ranged from 11 to 28oC, while pH varied from 6.6 to 10.7, and turbidity from 1.7 to 133 NTU. Electrical conductivity (EC), total dissolved solids (TDS) and salinity showed drastic variations (42.3-46693 μS/cm, 20.3–23350 mg/L and 0.02–33.8 PSU respectively). The concentrations of other parameters ranged as follows: chloride (3.7–168 mg/L); DO (6.9–11.1); BOD (0.6–9.4); COD (3.7–45.9); nitrite-nitrogen (0.02–0.21); nitrate-nitrogen (1–4.47); and orthophosphate (0.01–1.72). TC, FC and ENT counts were high and ranged from 1.9 × 102–3.8 × 107 cfu/100 mL, 0–3.0×105 cfu/100 mL and 0–5.3 × 105 cfu/100 mL for TC, FC and ENT respectively. Significantly (P<0.05) higher concentrations of FC and ENT were observed at the sampling sites located at the lower reaches of the river compared to the upper reaches. The FIB counts mostly exceeded the maximum limits recommended by national and international guidelines for safe fresh produce irrigation, domestic applications, full-contact recreation and livestock watering. Significant (P<0.01) positive correlations existed between TDS and salinity (r=0.921), between turbidity and each of TC (r=0.552) and FC (r=0.425), as well as between BOD and each of TC (r=0.282), FC (r=0.472) and ENT (r=0.552). Phosphate correlated positively with FC (r=0.424), and nitrate also with the same, FC (r=0.460). A strong positive correlation existed between FC and ENT (r=0.915). There existed a significant (P˂0.01) inverse correlation between enteric viruses and each of water temperature (r=-0.191) and pH (r=-0.234). No correlation could be deduced between enteric viruses and all the tested chemical and bacteriological parameters. HAV, HAdV, RoV and EnV were detected in 43.1percent, 34.7percent, 13.9percent and 9.7percent respectively of the total 72 water samples tested. Two or more viruses were detected in 22.2 percent of the samples. HAdV were detected at 5 of the 6 sampling sites with concentrations ranging from 1.2×101 genome copies (GC)/litre to 4.71×103 GC/litre. Epidemiologically important serotypes, Ad40/41 constituted 83.3percent, while Ad21 made up 16.7percent of all the HAdV detected. HAV was detected at all the sites in significantly (p < 0.05) varying concentrations that ranged from 1.5 × 101–1.9 × 105 GC/litre compared to RoV and EnV. Neither of RoV nor EnV was detected at any of the dams. The detected concentrations at the non-dam sites ranged from 2.5 × 101–2.1 × 103 GC/litre and 1.3 × 101–8.6 × 101 GC/litre for RoV and EnV respectively. The values for the estimated daily risks of enteric virus infection varied with sites and exposure scenario, and ranged from 7.31×10-3–1 (for HAdV), 4.23×10-2–6.54×10-1 (RoV), 2.32×10-4–1.73×10-1 (HAV) and 1.32×10-4–5.70×10-2 (EnV). The yearly risks of infection in individuals exposed to the river/dam water via drinking, recreational, domestic or irrigational activities were unacceptably high, exceeding the acceptable yearly risk of 0.01percent (10-4 infection/person/year) recommended by the USEPA for drinking water. The risks of illness and of death from infection ranged from 6.58×10-5–5.0×10-1 and 6.58×10-9–5.0×10-5 respectively. Data on the physicochemical and bacteriological parameters showed that the Buffalo River water quality was poor, and deteriorated in the plains compared to the upper reaches. These water quality data, the presence of enteric viruses and the QMRA data, that revealed unacceptably high risks of enteric virus infections, and of illness and mortality from the infections, show that the Buffalo River and its dams are contaminated waters that constitute significant public health hazards. Provision of adequate sanitary infrastructure will help prevent source water contamination, and public health education aimed at improving personal, household and community hygiene is imperative. Monitoring enteric viruses in rivers and source water dams is necessary and useful as a risk assessment tool for the exposed population. Future research should consider a comprehensive characterization of the detected viruses. This work is both a significant contribution to the molecular epidemiology of enteric viruses and the first report on molecular detection and quantification of enteric viruses in surface waters in the Eastern Cape. , Thesis (PhD) -- Faculty of Science and Agriculture, 2013
- Full Text:
- Date Issued: 2013-03
The culture of Penaeus Indicus Milne Edwards in experimental closed systems with special reference to water quality
- Authors: Gerhardt, Hedley Vernon
- Date: 1979
- Subjects: Penaeus Indicus , Aquatic animals , Water quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5595 , http://hdl.handle.net/10962/d1002045 , Penaeus Indicus , Aquatic animals , Water quality
- Description: This study embraces two aspects of closed system culture: (a) a comparative study of four different biological filtration treatments, and (b) a quantitative determination of the nitrogen flow in a particular biological filtration system. Twenty 0,5 g juvenile Penaeus indicus Milne Edwards were cultured for approximately two months in four different kinds of sea water recirculatory systems with bacterial filtration, algal filtration, algar plus bacterial filtration and water exchange (25% every 3 days). Growth was comparable to that found in the literature for P. indicus. Nitrification occurred in all systems irrespective of the type of biological filtration employed. Ammonia, nitrite and nitrate levels were reduced by the algae, but nitrate accumulated to approximately 30 mg NO¯³ -Nℓ¯¹ in those systems without algae. Depletion of trace elements (Cu, Fe, Zn, Hn and Co) by the algae did not occur due to trace metal replenishment from the addition of food. No marked changes occurred in the concentrations of the major cations (Ca⁺⁺, Mg⁺⁺, Na⁺ and K⁺), but a small increase in Ca⁺⁺ levels was detectable in those systems with oyster shell chips in the filtration medium. Only minor changes occurred in oxygen or pH values in the various systems tested. Inorganic carbon levels showed major increases in the algal filtration systems, while a slight drop occurred in the bacterial filtration systems. The increase in the algal filtration systems was thought to be due to the formation of carbonates and bicarbonates by the reaction of respiratory CO₂ with unionized ammonia and water. Suggestions are made as to how closed systems can be improved upon. By determining the rate of excretion of P.indicus as related to size and temperature, its faecal production, and the nitrogen content of P.indicus, its food and faeces, the nitrogen flow within a system could be calculated. P.indicus was found to have an assimilation efficiency of 88,93% and a food conversion ratio of 3,49:1. Of the total dietary nitrogen input into the system, P.indicus ingested 69,02% - 19,80% of which was used for growth, 41,58% excreted and 7,64% lost as faeces. The remaining 30,98% of the total nitrogen input can be regarded as excess food nitrogen. The total nitrogen loading on the biological filtration system was found to be 80,20% of the total input of dietary nitrogen. The ability of various types of filamentous algae to remove these nitrogen compounds was determined. Suggestions are made as to the application of this information on nitrogen flow to the culture of P.indicus
- Full Text:
- Date Issued: 1979
- Authors: Gerhardt, Hedley Vernon
- Date: 1979
- Subjects: Penaeus Indicus , Aquatic animals , Water quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5595 , http://hdl.handle.net/10962/d1002045 , Penaeus Indicus , Aquatic animals , Water quality
- Description: This study embraces two aspects of closed system culture: (a) a comparative study of four different biological filtration treatments, and (b) a quantitative determination of the nitrogen flow in a particular biological filtration system. Twenty 0,5 g juvenile Penaeus indicus Milne Edwards were cultured for approximately two months in four different kinds of sea water recirculatory systems with bacterial filtration, algal filtration, algar plus bacterial filtration and water exchange (25% every 3 days). Growth was comparable to that found in the literature for P. indicus. Nitrification occurred in all systems irrespective of the type of biological filtration employed. Ammonia, nitrite and nitrate levels were reduced by the algae, but nitrate accumulated to approximately 30 mg NO¯³ -Nℓ¯¹ in those systems without algae. Depletion of trace elements (Cu, Fe, Zn, Hn and Co) by the algae did not occur due to trace metal replenishment from the addition of food. No marked changes occurred in the concentrations of the major cations (Ca⁺⁺, Mg⁺⁺, Na⁺ and K⁺), but a small increase in Ca⁺⁺ levels was detectable in those systems with oyster shell chips in the filtration medium. Only minor changes occurred in oxygen or pH values in the various systems tested. Inorganic carbon levels showed major increases in the algal filtration systems, while a slight drop occurred in the bacterial filtration systems. The increase in the algal filtration systems was thought to be due to the formation of carbonates and bicarbonates by the reaction of respiratory CO₂ with unionized ammonia and water. Suggestions are made as to how closed systems can be improved upon. By determining the rate of excretion of P.indicus as related to size and temperature, its faecal production, and the nitrogen content of P.indicus, its food and faeces, the nitrogen flow within a system could be calculated. P.indicus was found to have an assimilation efficiency of 88,93% and a food conversion ratio of 3,49:1. Of the total dietary nitrogen input into the system, P.indicus ingested 69,02% - 19,80% of which was used for growth, 41,58% excreted and 7,64% lost as faeces. The remaining 30,98% of the total nitrogen input can be regarded as excess food nitrogen. The total nitrogen loading on the biological filtration system was found to be 80,20% of the total input of dietary nitrogen. The ability of various types of filamentous algae to remove these nitrogen compounds was determined. Suggestions are made as to the application of this information on nitrogen flow to the culture of P.indicus
- Full Text:
- Date Issued: 1979
- «
- ‹
- 1
- ›
- »