Interaction among Non-toxic Phytoplankton,Toxic Phytoplankton and Zooplankton: Inferences from Field Observations |
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Authors: | Shovonlal Roy Sabyasachi Bhattacharya Partha Das Joydev Chattopadhyay |
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Institution: | (1) Agricultural and Ecological Research Unit, Indian Statistical Institute, 203 B.T. Road, Kolkata, 700108, India |
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Abstract: | We explore the mutual dependencies and interactions among different groups of species of the plankton population, based on
an analysis of the long-term field observations carried out by our group in the North–West coast of the Bay of Bengal. The
plankton community is structured into three groups of species, namely, non-toxic phytoplankton (NTP), toxic phytoplankton
(TPP) and zooplankton. To find the pair-wise dependencies among the three groups of plankton, Pearson and partial correlation
coefficients are calculated. To explore the simultaneous interaction among all the three groups, a time series analysis is
performed. Following an Expectation Maximization (E-M) algorithm, those data points which are missing due to irregularities
in sampling are estimated, and with the completed data set a Vector Auto-Regressive (VAR) model is analyzed. The overall analysis
demonstrates that toxin-producing phytoplankton play two distinct roles: the inhibition on consumption of toxic substances
reduces the abundance of zooplankton, and the toxic materials released by TPP significantly compensate for the competitive
disadvantages among phytoplankton species. Our study suggests that the presence of TPP might be a possible cause for the generation
of a complex interaction among the large number of phytoplankton and zooplankton species that might be responsible for the
prolonged coexistence of the plankton species in a fluctuating biomass. |
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Keywords: | Coexistence Paradox of plankton Toxin-producing plankton Partial correlation Time series E-M algorithm VAR model |
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