Natural Resources, School of

 

Date of this Version

12-2012

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Natural Resource Sciences, Under the Supervision of Professor Kyle D. Hoagland. Lincoln, Nebraska: December, 2012

Copyright (c) 2012 Rebecca Alexander

Abstract

Cyanobacteria are a major concern in Nebraska reservoirs and are capable of producing toxins that can cause skin irritations and gastrointestinal problems, as well as affect the nervous system. It is important to determine the mechanisms that can cause cyanobacteria blooms due to the effect they can have on human health. The interaction of zooplankton and other phytoplankton groups with cyanobacteria is important because there is a biological component in surface waters that should be taken into consideration along with the physical and chemical parameters that have been noted to promote cyanobacteria. For example, zooplankton have the ability to alter the phytoplankton composition through their grazing and previous research has shown that cyanobacteria can have diverse effects on different zooplankton, which could promote and perpetuate cyanobacteria. Weekly samples were collected from six Nebraska reservoirs and analyzed to determine the interactions of zooplankton and phytoplankton with cyanobacteria using two generalized additive models with cyanobacteria relative percentage or cyanobacteria biovolume as explanatory variables. In most cases, cyanobacteria relative percentage and biovolume had similar effects on phytoplankton and zooplankton groups with little difference in the predicted biovolume/biomass or density. Chemical and physical data collected from the reservoirs were analyzed with spearman rank correlations to determine their relationships with cyanobacteria biovolume. Including biological, chemical and physical parameters to ascertain the interactions and relationships with cyanobacteria can help establish grounds for management techniques, such as biomanipulation. Biomanipulation can prove to have positive results in surface waters, but further research is needed to determine its effectiveness in Nebraska reservoirs. This study provides the first steps in helping to establish its possible effectiveness by determining the interactions of zooplankton and phytoplankton with cyanobacteria in reservoirs.

Adviser: Kyle D. Hoagland