Community Size Distributions Reflect Niche Differentiation among Phytoplankton in the Sundarbans Estuarine Ecosystem

Prasad, Praveen V. (2015) Community Size Distributions Reflect Niche Differentiation among Phytoplankton in the Sundarbans Estuarine Ecosystem. Masters thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

Species coexist in resource limited environment by mutually tolerating each other, partitioning the niche, exhibiting difference in behavior . Coexist is to live together in the same place, at the same time, with one another. We were interested to find how different varieties of phtoplanktons which interact biotically and abiotically coexist together in a resource limited environment like sunderbans. Though various studies have conducted for coexistence in different species in different conditions, the general mechanism of species coexistence is still unknown. Theoretical explanations behind coexistence vary from simple niche based mechanisms to neutral mechanisms in various systems. Niche based model says that increase in negative intraspecific interaction compared to interspecific interaction stabilizes the ecosystem whereas in neutral mechanism states that by decreasing the fitness difference between species leads to coexistence .From previous studies its well-known that species interacting in spatially homogeneous environment coexist only when there is spatial niche differences between them. These species does not exhibit differential responses to the environment but the responses they are showing is solely dependent on competition mostly interspecific. In case of species interacting in a heterogeneous environment coexist when there is a growth density covariance occurs where species change the density of growth a sort of niche partitioning. This study primarily aims to find out the various underlying patterns behind coexistence of distinct Morphology Based Functional Groups(MBFG) Sunderban phytoplanktons. We collected samples from different locations of site with different conditions (distance from fresh water source) and analyzed in field and lab. Further we hypothesized and concluded that tradeoffs exist for different group for coexistence. We found that tradeoff for nutrients such as silicate and nitrate are well pronounced in our system. Size is a good predictor of metabolism and a general relation between size and metabolism is predicated as M α S⁽¹/³⁾. We identified different morphology based functional groups namely small irregular cells, small circular/oval cells, large circular/oval cells, rectangular shaped cells, filamentous cells, large irregular cells. In our present study we were able to conclude that smaller group of organism require high amount of silicate and nitrate compared to larger MBFG may be due to their higher specific area wise metabolic rate.

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