Trends in nitrate-nitrogen, nitrite-nitrogen and phosphorus concentration in Ebonyi river, Nigeria

A baseline study of the limnological integrity of Ebonyi River, a tropical lotic system in south-eastern Nigeria was conducted between September 2006 and February 2008 to assess its potential in enhancing fisheries production for the benefit of the rural poor, who depend on the resources of the river for survival. The parameters measured were nitrate-nitrogen, nitrite-nitrogen and phosphate-phosphorus. Results show that nitrate varied between 40.43mg/L in September 2006 and 1.73mg/L in December 2007, Showing significant difference (P<0.01) among months. The values recorded for nitrites varied between 0.2mg/L in September 2006 and 0.4mg/L in February 2008, showing significant (P<0.01) variation among months. Values recorded for phosphorus was highest (0.05mg/L) in the month of October 2006 while the least mean value (0.32mg/L) was recorded in the month of May 2007 and showed significant (p<0.01) variation in monthly means. It was concluded that the values of the measured parameters falls within tolerable range for enhanced fisheries development in the area. KEYWORDS: Limnology, Tropical, River, Monthly, Mean, Variation

Influence of nitrogen salts on growth and physiological responses of Rhizophora apiculata Blume in non-aerated water culture

Influence of two different forms of nitrogen on growth and physiological aspects of water-cultured seedlings of Rhizophora apiculata was studied. Of the two forms of nitrogen supplied to the growth medium, ammonium nitrogen was better than nitrate nitrogen by exhibiting increased dry matter production, shoot length, leaf area and also enhanced the contents of carotenoids, chlorophylls and their presence in photosystems and light harvesting protein complex.

Plant nutrients and major ions in the Little Sea, Studland, Dorset

This short paper records some measurements made on the Little Sea, a shallow, coastal, acidic lake on Studland Heath, Dorset. The lake, formed about 100 years ago by dunes cutting off a sea inlet, has not received any input of agricultural fertilizers or other waste products for at least the last 30 years. It is a Site of Special Scientific Interest (SSSI). Samples of surface water were taken from the northern and southern ends of the lake at 3-monthly intervals, from July 1995 to April 1996. The first samples in July 1995 were taken during a period of drought; rain, sometimes very heavy, came in late September. With the exception of silicate, potassium and phosphate, there were no large changes in plant nutrient concentrations during the year. The concentration of nitrate-nitrogen was very low (close to the limits of analytical detection), but total phosphorus at ca. 30 mu g per litre was similar to concentrations found in some of the Cumbrian eutrophic lakes. The large number of algal species at low cell/colony concentrations suggested that the lake is mesotrophic. Sodium, chloride and magnesium in the lake water were close to the same proportions as those found in sea water. Dry and wet deposition of sea-salts on the lake surface and its catchment area probably is the major source of sodium, magnesium and chloride ions in the lake, and also accounts for about half of the mean potassium and sulphate concentrations.

Limnological survey of the Cheshire, Shropshire, Staffordshire Meres. Interim data report

This is the Limnological survey of the Cheshire, Shropshire, and Staffordshire Meres: Interim data report produced by the University of Liverpool in 1992. This report looks at the Limnological survey data from Cheshire, Shropshire and Staffordshire Meres. Limnological data of the report covers: changes in water conductivity, Phenolphthalein Alkalinity, Total Alkalinity, pH, Chloride concentrations, Soluble reactive Phosphorus, Total Phosphorus, Nitrate Nitrogen, Ammonium Nitrogen, Silicate, Chlorophyll, Carotenoids, Secci disk depth, changes in Trophic Score, changes in DAFOR scores for submerged and floating plants and Oxygen saturation during summer. This report also contains Seasonal maps of different Meres. The more important limnological data are plotted as seasonal means in relation to the sampling sites. Conductivity is shown as μSiemens per cm, alkalinity as milliequivalents per litre. Total and soluble reactive (available inorganic) phosphorus are shown in terms of P in μg per litre. Nitrate and ammonium are shown in terms of N in mg per litre. Chlorophyll a is given as μg per litre. A profile of oxygen saturation is shown. These profiles were obtained towards the middle of the day in August and September.

Performance of Amblypharyngodon mola with Barbodes gonionotus, Cyprinus carpio and Macrobrachium rosenbergii in rice-fish culture system

An experiment was conducted to assess the performance of mola (Amblyphmyngodon mola) in rice fish culture system with freshwater prawn Macrobrachium rosenbergii), Thai silver barb (Bm·bades ganianotus) and common carp (Cyprinus cmpia) for a period of 4 months at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, Bangladesh. Four treatments viz., treatment-I (T1) with A. mala and M. rosenbergii; treatmen t-II (T2) with A. mala, M. rosenbergii and B. gonianatus ; treatmentIII (T3) with A. mala, 1Vf. rosenbergii and C. cmpia, and treatment- IV (T4) as control (without fish) were used in triplicate. All treatments were equally fertilized with urea (200 kg/ha), TSP (150 kg/ha) and MP (75 kg/ha). The mean values of water quality parameters viz., temperature, dissolved oxygen, pH, nitrate-nitrogen showed a very small variations among different treatments, but phosphate-phosphorus and chlorophyll-a were relatively higher in T4 without fish (i.e., control). The fish production of 480.5 kg/ha in T3 was significantly higher than that of 355.6 kg/ha T2 and 223.8 kg/ha in T 1• The values of soil organic matter, total-nitrogen, phosphorus and potassium at harvest were significantly (P<0.05) higher in the treatments with fish than without fish, but pH did not show any significant differences. The yield of rice grain and straw was also obtained significantly (P<0.05) higher in the treatments with fish. The increase in grain was higher over the control by 11.81%, 9.41% and 14.76% and that in straw was by 9.83%, 4.77% and 13.29% in Tl> T2, and T3 respectively.

Seasonal dynamics in the occurrence and abundance of Pseudo-nitzschia species in the Maheshkhali channel of the Bay of Bengal, Bangladesh

Occurrence and abundance of Pseudo-nitzschia spp. at the mouth of the Maheshkhali channel of the Bay of Bengal, Bangladesh were studied. Plankton and water samples were collected monthly from the sub-surface water during high tide at daytime from June 2000 to May 2001. Four species of Pseudo-nitzschia, namely P. pungens, P. pseudodelicatissima, P. delicatissima and P. australis were identified and among them the first three were most commonly encountered and they varied seasonally. Pseudo-nitzschia delicatissima was the dominant species during the autumn and winter months, whereas P. pungens was dominant during the summer and spring months. Pseudo-nitzschia pseudodelicatissima exhibited its highest abundance level during the summer. Surface water temperature, salinity, nitrate-nitrogen (N03-N) and phosphate-phosphorus (P04-P) were recorded and their relationship with the occurrence and abundance of Pseudo-nitzschia species were studied. At the mouth of the Maheshkhali channel, Pseudo-nitzschia cell density was highest in late autumn (November) when highest salinity (35 o/oo) and P04-P (3.2 mg/l) concentrations and low temperature (23 °C) were recorded.

Euglenophytes in aquaculture ponds - their ecology and role in fish production

The ecology of euglenophytes and their role in fish production were studied in 12 small earthen ponds beside the Faculty of Fisheries, BAU from July to November 2001. Four experiments each with three replications were conducted and those were as follows: pond treated with both poultry droppings and cowdung (T1); pond treated with only poultry droppings (T2), and pond treated with only poultry droppings (T3), while the control (T4) where no organic manure was applied. Fishes comprising of rohu (Labeo rohita), catla ( Catla catla), mrigal ( Cirrhinus cirrhosus), silver carp (Hypophthalmichthys molitrix) and silver barb (Barbonymus gonionotus) were stocked at the same stocking density of (10,621 fish/ha) and species ratio (1:1:1:2:2). The stocked fishes were fed with a common supplemental diet comprising of mustard oil cake and rice polish (1:1) at the rate of 4% of body weight per day. The highest cell density of euglenophytes was found in the ponds of T2, where poultry droppings were applied and was followed by T1, where both poultry droppings and cow dung were applied. Higher temperature, nitrate-nitrogen, phosphate-phosphorous and acidic pH were found to be conducive for the bloom of noxious euglenophytes. The bloom was found to use up most of the nutrients resulting in reduction in the growth of beneficial plankters and planktivorous fishes. The SGR (%/day) of catla, rohu and mrigal was lower during heavy bloom period while that of silver carp and silver barb were comparatively higher. The mortality of fishes in a pond of T2 during the bloom period was possibly due to formation of anoxic situation (dissolved oxygen level as low as 0.34 mg/1) in the early mornings through bacterial decomposition of the settled dead individuals or due to the combined effect of anoxic situation and toxic metabolite secretion by the euglenophytes.

Microalgal community structure in experimental carp-pangasiid catfish polyculture ponds

Microalgal community structure in experimental carp-pangasiid catfish polyculture ponds under four different stocking rates (treatments) each with three replications in the Field Laboratory of the Faculty Fisheries, Bangladesh Agricultural University, Mymensingh was studied. A total of 38 microalgal genera were identified under four major groups: 18 genera belong to Chlorophyceae, 9 to Cyanophyceae, 8 to Bacillariophyceae and 3 to Euglenophyceae. Chlorophyceae was abundant in all treatments followed by Cyanophyceae, Bacillariophyceae and Euglenophyceae throughout the study period. The cell densities of total microalgal population varied between 51.66x10^3 cells/L in June in T1 and 126.4x10^3 cells/L in August in T2. The appearance of Microcysris, Oscillatoria, Gomphospheria, Hildenbrandia, Chlorella, Scenedesmus, Cyclotella, Navicula, Nitzschia, Euglena and Phacus as dominant genera throughout the study period may related to sufficient nutrient availability, good light conditions and high growth rate of these genera. Water quality parameters of the experimental ponds were within suitable range for microalgal production and fish culture though the nutrient (nitrate-nitrogen and phosphate-phosphorus) concentrations were high. The factors involved in structuring a phytoplankton community arise from the relationship generated by physical, chemical and biological conditions especially the stocked planktivorous carps. Microalgal bloom formation is very common in pangasiid catfish monoculture ponds but in the present study bloom was not formed and the algal species diversity was found to be slightly increased with the study period. The introduction carps of carps in the experimental ponds might have helped in controlling the microalgal bloom formation and maintenance of the species diversity.

Noxious euglenophytes bloom in fertilized fish ponds

A study was carried out in nine fertilized fish ponds under three treatments at Bangladesh Agricultural University, Mymensingh, Bangladesh, to record the influence of different fertilizers on noxious euglenophytes bloom. Some water quality parameters (viz., temperature, pH, phosphate-phosphorus, nitrate-nitrogen and chlorophyll-a) and phytoplankton populations were monitored at certain intervals. During the study period, three genera of euglenophytes such as Euglena, Phacus and Trachelomonas were recorded of which Euglena was most dominant. Significantly (p<0.05) higher cell density of euglenophytes was observed in the ponds treated with chicken manure followed by the ponds treated with both cow dung and chicken manures and the ponds treated with only cow dung. The higher cell density of euglenophytes was explained by acidic pH (around 6.5) and higher phosphate-phosphorus (1.37 mg/1) and nitrate-nitrogen (1.47 mg/I) concentrations. The population size of euglenophytes showed positive correlation with phosphate-phosphorus and nitrate-nitrogen concentration while negative with pH. Nutrient enrichment and acidic pH enhanced the growth of euglenophytes but reduced the growth of chlorophytes and bacillariophytes.

The influence of nitrogen and phosphorus on the growth of a diatom Skeletonema costatum (Greville) Cleve

Nitrogen and phosphorus requirements of a chain-forming diatom, Skeletonema costatum (Greville) Cleve, collected from Yatsushiro Sea, Japan, were investigated in a laboratory culture experiment. Sodium nitrate and sodium glycerophosphate were used as nitrogen and phosphorus sources, respectively. Cultures were grown in modified Provasoli's ASP2NTA medium (Provasoli et al. 1957) at 25±1°C, light intensity 60 µE mˉ² secˉ¹ and photoperiod 12:12-h, L:D cycle. Optimum growth was observed at nitrate concentrations of 3-10 mglˉ¹ and phosphate concentrations of 1.5-15 mglˉ¹. Adequate growth was also found at the nitrate concentration of up to as high as 300 mglˉ¹. Significantly poorer growth was found at lower nitrate (<3.0 mglˉ¹) and higher phosphate (>15 mglˉ¹) concentrations. From the present study, it is concluded that S. costatum can grow well at wide ranges of nitrate concentrations but is sensitive to higher phosphate concentrations.