Date of Award

Fall 2018

Project Type


Program or Major

Earth Sciences

Degree Name

Master of Science

First Advisor

William C Clyde

Second Advisor

James F Haney

Third Advisor

James M Pringle


In 1961 Hutchinson proposed the “Paradox of the Plankton” questioning how sympatric planktonic species can coexist for long periods of time while seemingly avoiding the competitive exclusion principle. As this ‘paradox’ became a focus of inquiry, one researcher conducted a 2-year study (1961-1962; Tappa 1965) on Aziscohos Lake Daphnia to address the question. While the study did not solve the enigma, it provided a detailed record of the dynamics and interactions of six coexisting species. Aziscohos Lake and its zooplankton have not been studied since. This study revisits the ‘paradox of the plankton’ by establishing the dynamics of extant Daphnid populations within Aziscohos Lake. Analysis of plankton tows indicate that five species (D. catawba, D. ambigua, D. g. mendotae, D.retrocurva, D. dubia) from Tappa’s study are still present in addition to three species (D. rosea, D. schødleri, D. parvula) recorded for the first time in Aziscohos Lake. This composition is unusually high given that the typical lake has between 1 and 3 species of Daphnia. It is proposed here that a seasonal compression of the littoral region from drawdowns of Aziscohos Lake is forcing littoral species into direct competition and overlap with pelagic species. This results in a higher species richness from a pelagic sample than the average lake that does not undergo such drastic lake level fluctuations. Further research of the littoral zone of Aziscohos Lake is recommended, as all previous studies have focused on the pelagic zone.