B. B. Jana

The life history parameters of Diaphanosoma excisum (Cladocera), grown in different culturing media

Life history parameters of Diaphanosoma excisum (SARS) were derived from culture tube experiments with media comprising mohua oil cake, mustard oil cake, cow dung and rice bran. Body length, longevity, fecundity and progeny production were highest in rice bran medium. First reproduction time (A) in different media ranged from 2 to 6 days, while the reproduction peak (T) varied from 4 to 13 days. The total offspring per female (S) was directly dependent upon the mean number of eggs per female per life span. The intrinsic (r) and finite rate (er) of natural increase were larger for rice bran than for other media.

Seasonal and spatial distribution pattern of nitrogen fixing bacteria in fish ponds under different management systems

Enumeration of nitrogen fixing bacterial population in water and sediment samples of six fish farming ponds (polyculture, monoculture and traditional systems) over a period of two and a half years revealed significant differences between the culture systems with maximal and lowest counts in the monoculture and traditional systems, respectively. Polynomial equations of the 2nd to 4th degree were used to represent the observed seasonal data in these ponds. The bacterial populations peaked in summer, while the lowest count was observed in winter. The environmental factors such as pH, different species of nitrogen, dissolved organic carbon were responsible for the seasonal changes in nitrogen fixing bacteria.

The plankton ecology of some thermal springs in West Bengal, India

Estimates of planktonic growth kinetics in relation to the thermal environment were made over a two year period in three hot springs and one cold one located in West Bengal, India. A very characteristic feature of the Saubhagya Kund (43–49°C) and Papahara (46–51°C) was the abundance of phytoplankton, always dominated by blue-green algae. This situation changed in the other two springs where zooplankton was an essential component. The determination of the species diversity index indicated that the graph of cumulative species of plankton versus logarithm of individuals was roughly linear in Saubhagya Kund and Papahara, whereas in the other two a logistic curve was the result. The seasonal distribution of Myxophyceae/Phytoplankton was dependant upon the annual phosphorous cycle (P < 0.0001) in all the thermal waters studied. That the population dynamics of diatoms responded inversely to the level of phosphate (P < 0.05) has been clearly manifested in Swetganga (37–46°C). The variation in the silicate content of the water throughout the year has been found responsible for the seasonal succession of diatoms in some of the waters (P < 0.001). The multiple correlation between phosphate, silicate, dissolved oxygen and pH and Myxophyceae/Phytoplankton was significant in the case of Papahara (P < 0.01) and Swetganga (P < 0.05). Similarly, the multiple correlation between these factors and Bacillariophyceae was significant in Saubhagya Kund (P < 0.01). In the non-thermal water Jibatsa Kund (22–39°C), the multiple correlation between these factors and Phytoplankton was, however, not significant (P > 0.05).

Primary production and bacterioplankton in fish ponds with mono and polyculture

Estimates of primary production in relation to bacterioplankton growth kinetics have been made in three fish ponds with mono and polyculture in the Fish Farm Nivka, Kiev, USSR. Since the basic process of primary production is dependent upon such prevailing conditions as temperature, light and nutrient rather than upon the introduction of fish species, almost similar production rates were obtained in these ponds, with the variance ratio found not significantly different from zero (P > 0.05). So was the case with bacterioplankton growth kinetics (P > 0.05). A maximal gross production coupled with a bacterioplankton peak was demonstrated in the summer month of July with the rise of temperature of the water, while minimal production was observed in September. The effect of season was highly significant (P < 0.001) upon both primary production and bacterioplankton. Extreme deficiency of the net photosynthetic production of O2 was observed in summer due to less prevalence of phytoplanktonic algae as a consequence of heavy grazing by the herbivorous fishes at the time of their active growth. A plot of biochemical oxygen demand as function of the respiratory loss of O2 due t0 bacterial population showed a direct linear relationship (P < 0.001). Lack of definite correlation (P > 0.05) was indicated between the BOD and the total bacterioplankton population. There existed no definite relationship (P > 0.05) between primary production and bacterioplankton, perhaps because of the very low percentage of autotrophic photosynthetic bacteria and abundance of heterotrophic bacteria in the composition of total bacterioplankton.

Sediment Raking as a Tool for Enhancement of Phosphate and Productivity of Water in Tropical Pond System

Changes of orthophosphate in water, induced by raking of surface sediment in various ways, were compared. Twelve limnocorrals were installed in a shallow mesotrophic pond using four treatments with triplicate replication:(1) raking of surface sediment (R) by means of a rake for 5min per week (2) fish (F), by introducing six common carp and two silver carp per limnocorral, (3) raking plus fish (R+F) and (4) control (C), without raking and fishless. After day 122, treatments were reversed in limnocorrals by␣removing (netting) or introducing fish and stopping or initiating raking. Samples of water and sediment were collected from each limnocorral at weekly interval and monitored for orthophosphate (OP), primary productivity, phosphate solubilizing bacteria (PSB) and sediment available phosphorus. Raking in presence of fish caused 280 and 160% increase in OP concentrations in surface and bottom water, respectively, as compared with raking in absence of fish. Net effects of fish and raking were 13-81 and 26-241%, respectively in surface water and 48-100 and 46-95% in bottom water. This implied that in bottom water, net raking effect was 13-161% greater than net fish effect. Increase in PSB population, due to raking plus␣fish (R+F) was 6-82% higher than increase by fish alone (F). Responses of available-P in sediment were opposite to that of water, being highest in concentration in control (C) followed by fish (F), raking (R) and raking plus fish (R+F). The primary productivity showed variations parallel with that of orthophosphate of water. This suggests that raking accelerated the transformations of available-P from␣sediment to overlying water mediated through oxygen-dependent sediment water exchange mechanisms.

Growth characteristics of the heterotrophic bacterial population of water and bottom sediments in tanks under different trophic conditions

Treatment of single and double doses of fertilizers had a definite response on the bacterial population of water and bottom sediments in tanks after 7 days (F2,21 ⩾ 3.61; P < 0.05), but did not cause any significant change after day 32 (F2,18 ⩽ 1.67; P > 0.05). Although the generation time of water bacteria did not vary much in these treatments of trophic gradients (P > 0.05), there was always a distinct variation (P < 0.01) in the generation time of the bacterial population of bottom sediments. The population size of water bacteria was shown to maintain an inverse relationship with the diurnal variation of temperature (P < 0.05) and dissolved oxygen (P < 0.05) of the water. The changes in the size of the bacterial population of water were positively correlated with the variations of hardness (P < 0.05), chloride (P < 0.05) and ammonia nitrogen (P < 0.05) of water. Although the relationships between the heterotrophic bacterial population and the inorganic phosphate of water was not convincing (P > 0.05), an inverse relationship was established between the bacterial community of bottom sediments and the phosphate content of the water (P < 0.01).

Distribution pattern of sulphate reducing and thiosulphate oxidizing bacterial populations in fish ponds of differing farming managements

The population size of SRB and TOB was enumerated at bimonthly intervals from water and sediment samples of six fish ponds (polyculture, monoculture and traditional systems) over a period of two and a half years. Density of SRB and TOB was maximal in polyculture and minimal in traditional systems of fish farming. Using sine and cosine waves of periodic functions or polynomial equations of high order, seasonal changes in the numbers of SRB and TOB were represented; the former occurred in largest numbers in summer while the latter in winter. Step wise multiple regression analysis revealed that organic carbon, organic matter, phosphate and different forms of N were important attributes to the seasonal changes of SRB and TOB in these fish ponds.