J. Pal - Academia.edu (original) (raw)
Supervisors: Prof. Joydev Chattopadhyay and Prof. Bidhan Chandra Patra
less
Uploads
Papers by J. Pal
Dedicated to celebrate the 6o-th birth day of Professor Gaston M. N'Guerekata.
Physica A: Statistical Mechanics and its Applications, 2013
• We formulate the fractional counterpart of the Rosenzweig model. • We analyze the stability of ... more • We formulate the fractional counterpart of the Rosenzweig model. • We analyze the stability of this fractional order model. • We identify a threshold for the memory effect parameter. • Below this threshold value the system is always stable independent of enrichment.
Harmful algal blooms (HABs) have several adverse effects and have drawn considerable scientific a... more Harmful algal blooms (HABs) have several adverse effects and have drawn considerable scientific attention in recent years. In the present paper, first, we considered the field observations carried out in the North-West coast of Bay of Bengal, India, and observed that single harmful phytoplankton-zooplankton system shows bloom phenomenon and the average biomass levels of the species in this case are higher compare to the situation when two harmful phytoplanktons are present. The presence of two harmful phytoplanktons in the system reduces the high abundance of the population showing considerable decrease in HABs. Next, motivated from our experiment we proposed a deterministic model consisting of two harmful phytoplanktons and zooplankton with an additional factor that the harmful-phytoplankton reduce the growth of zooplankton by toxic substances. To observe the effect of environmental variability in the deterministic model we modified the system into a stochastic model by applying stochastic perturbation in the form of white noise. The dynamics of both deterministic and stochastic model were studied and threshold values of the inhibition rate as well as noise intensity were calculated to obtain stable coexistence of the species. We further observed that intensity of white noise and competition between the species play important roles to reduce the bloom situation. The physical interpretation of our mathematical analysis and numerical simulations suggest the termination of planktonic blooms is possible due to competition between two or more phytoplankton as well as through low intensity of external noise. Our analytical findings support our field observations.
Problem statement: Selectivity is common in predator-prey interaction but the selection mechanism... more Problem statement: Selectivity is common in predator-prey interaction but the selection mechanism is still unexplored and a debatable issue in modern theoretical and experimental ecology for numerous species across the globe. In present investigation we emphasized the hypothesis that the zooplankton is less inclined to opt the food based on size selectivity criteria than the preferential selectivity for the safe non-toxic food species. Approach: As a test bed we select one nontoxic phytoplankton (Chaetocerous gracilis), one toxic phytoplankton (Microcystis aeruginosa) and one zooplankton (Artemia salina). Initially the experiment is setup through the small batch cultures of Nontoxic (NTP) and toxic Phytoplankton (TPP). Both the strains of phytoplankton are collected from the deltaic region of river Subarnarekha (87°31"E and 21°37"N) and the isolation is done in the laboratory. Similarly batches of zooplankton (Brand: Red Top, USA) are also hatched and maintained at optimal conditions in the laboratory. We set off the experiments with the physical parameters viz. Photo period: 12: 12 L: D cycle, Temperature: 26-27°C, Salinity: 10 ppt and pH of the medium 7.5. To evaluate our hypothesis in restricted environment we have introduced the zooplankton in a 3 liter beaker with 75: 25 (TPP: NTP) food ratio. Biological activities (feeding) are monitored for each of the species with regular recorded biomass count on each experimental day till the predator population goes to extinct. Results: The mean biomass profile of zooplankton remains more or less constant at the initial stage but a sharp decline trend has been observed after the 4th day of the experiment. A similar trend has been observed for the mean biomass profile of NTP leading the population toward extinction after 6th experimental day. The entire mean biomass profile trend of TPP can be interpreted as a convolution of three growth pulses viz., initially positive, followed by a negative and terminating with a positive growth. To evaluate the bias in the result of experiment we have estimated the variance levels of sample biomasses for each of the experimental time points for each of the three species. Conclusion: The observed stable nature of the zooplankton biomass may be due to initial NTP uptakes but a sudden decline suggests that they are forced to feed on the TPP for survival. In absence of grazing pressure, TPP initially showed a mild positive growth but when the predator switch to TPP for food it shows a negative growth and finally due to rapid mortality of zooplankton and excretal nutrient input the growth rate again kicks up. In summary we conclude that the zooplankter (Artemia salina) can discriminate toxic and nontoxic food species and more inclined toward the non-toxic species if the resource available. But shortage of nontoxic species, force them to feed on toxic one, in spite of drastic adverse effect on its survival.
Dedicated to celebrate the 6o-th birth day of Professor Gaston M. N'Guerekata.
Physica A: Statistical Mechanics and its Applications, 2013
• We formulate the fractional counterpart of the Rosenzweig model. • We analyze the stability of ... more • We formulate the fractional counterpart of the Rosenzweig model. • We analyze the stability of this fractional order model. • We identify a threshold for the memory effect parameter. • Below this threshold value the system is always stable independent of enrichment.
Harmful algal blooms (HABs) have several adverse effects and have drawn considerable scientific a... more Harmful algal blooms (HABs) have several adverse effects and have drawn considerable scientific attention in recent years. In the present paper, first, we considered the field observations carried out in the North-West coast of Bay of Bengal, India, and observed that single harmful phytoplankton-zooplankton system shows bloom phenomenon and the average biomass levels of the species in this case are higher compare to the situation when two harmful phytoplanktons are present. The presence of two harmful phytoplanktons in the system reduces the high abundance of the population showing considerable decrease in HABs. Next, motivated from our experiment we proposed a deterministic model consisting of two harmful phytoplanktons and zooplankton with an additional factor that the harmful-phytoplankton reduce the growth of zooplankton by toxic substances. To observe the effect of environmental variability in the deterministic model we modified the system into a stochastic model by applying stochastic perturbation in the form of white noise. The dynamics of both deterministic and stochastic model were studied and threshold values of the inhibition rate as well as noise intensity were calculated to obtain stable coexistence of the species. We further observed that intensity of white noise and competition between the species play important roles to reduce the bloom situation. The physical interpretation of our mathematical analysis and numerical simulations suggest the termination of planktonic blooms is possible due to competition between two or more phytoplankton as well as through low intensity of external noise. Our analytical findings support our field observations.
Problem statement: Selectivity is common in predator-prey interaction but the selection mechanism... more Problem statement: Selectivity is common in predator-prey interaction but the selection mechanism is still unexplored and a debatable issue in modern theoretical and experimental ecology for numerous species across the globe. In present investigation we emphasized the hypothesis that the zooplankton is less inclined to opt the food based on size selectivity criteria than the preferential selectivity for the safe non-toxic food species. Approach: As a test bed we select one nontoxic phytoplankton (Chaetocerous gracilis), one toxic phytoplankton (Microcystis aeruginosa) and one zooplankton (Artemia salina). Initially the experiment is setup through the small batch cultures of Nontoxic (NTP) and toxic Phytoplankton (TPP). Both the strains of phytoplankton are collected from the deltaic region of river Subarnarekha (87°31"E and 21°37"N) and the isolation is done in the laboratory. Similarly batches of zooplankton (Brand: Red Top, USA) are also hatched and maintained at optimal conditions in the laboratory. We set off the experiments with the physical parameters viz. Photo period: 12: 12 L: D cycle, Temperature: 26-27°C, Salinity: 10 ppt and pH of the medium 7.5. To evaluate our hypothesis in restricted environment we have introduced the zooplankton in a 3 liter beaker with 75: 25 (TPP: NTP) food ratio. Biological activities (feeding) are monitored for each of the species with regular recorded biomass count on each experimental day till the predator population goes to extinct. Results: The mean biomass profile of zooplankton remains more or less constant at the initial stage but a sharp decline trend has been observed after the 4th day of the experiment. A similar trend has been observed for the mean biomass profile of NTP leading the population toward extinction after 6th experimental day. The entire mean biomass profile trend of TPP can be interpreted as a convolution of three growth pulses viz., initially positive, followed by a negative and terminating with a positive growth. To evaluate the bias in the result of experiment we have estimated the variance levels of sample biomasses for each of the experimental time points for each of the three species. Conclusion: The observed stable nature of the zooplankton biomass may be due to initial NTP uptakes but a sudden decline suggests that they are forced to feed on the TPP for survival. In absence of grazing pressure, TPP initially showed a mild positive growth but when the predator switch to TPP for food it shows a negative growth and finally due to rapid mortality of zooplankton and excretal nutrient input the growth rate again kicks up. In summary we conclude that the zooplankter (Artemia salina) can discriminate toxic and nontoxic food species and more inclined toward the non-toxic species if the resource available. But shortage of nontoxic species, force them to feed on toxic one, in spite of drastic adverse effect on its survival.