Interaction coefficients in the Lake Shira algal-bacterial community

Abstract

A new method is proposed to evaluate the interaction coefficients in microbial communities interacting due to physical-chemical environmental factors. This method differs from the classical one suggested by E.P.Odum. Redefinition of the interaction coefficients allows the evaluation of the experimental (actual) and theoretical values of the coefficients for the hypothetical interaction layout. The interaction layout is considered to be a set of factors, the values of their transformation ratios and the form of dependence of a population's specific growth rate on these factors. A comparison of theoretical and experimental values of interaction coefficients enables us to assess the adequacy of the hypothetical interaction scheme in the microbial communities. The aim of the work is to test the suggested method on a natural algal-bacterial community of Shira Lake (Khakasia, Russia), which has been the object of detailed and concerted limnological studies and for which detailed data are available. Feedback coefficients of phyto- and bacterioplankton and the coefficients of influence of phytoplankton on bacterioplankton have been defined. Dominance of negative experimental IC values has been experimentally shown, which is indicative of the negative feedback in bacterio- and phytoplankton links of Shira Lake and of negative interpopulation (phytoplankton on bacterioplankton) interactions. The considerable differences observed between the experimental and theoretical coefficients indicates inadequacy of the assumed interaction layout of the community under study. Further investigations are needed to provide a precise sketch of the interactions.