The Effects of Initial Cell Density on the Growth and Proliferation of the Potentially Toxic Cyanobacterium &amp;lt;i&amp;gt;Microcystis aeruginosa&amp;lt;/i&amp;gt;

Robert M Dunn,Kalina M Manoylov

doi:10.4236/jep.2016.79108

Abstract

Increasing input of nutrients is leading to significant eutrophication in aquatic systems across the globe. Toxin production in those blooms is correlated with high cell density. A study was done to investigate the effects of initial cell density on the growth rate of the potentially toxic cyanobacterium Microcystis aeruginosa, in unfiltered lake water as well a common algal growth medium under laboratory conditions. Five treatments were established in the laboratory varying the initial cell density of M. aeruginosa and the growth medium. Unfiltered lake water was inoculated with a low, medium, and high initial cell density and Bold’s medium was inoculated with low and high initial cell densities. There was a significant difference in final cell density between the lake water treatments with the high inoculum of cell treatment reaching the highest final cell density. There was also a significant difference in final cell density between the Bold’s medium treatments. These results indicate there is a relationship between initial cell density of M. aeruginosa and final cell density, however, the results are similar when nutrients are available. Diverse algal communities can keep toxin producing algae in low density therefore precluding the need of toxin production.

Highlights

Rapid growth and acceleration of phytoplankton biomass, usually associated with eutrophication, is commonly termed as an algal bloom [1] [2]
The lake water collected in March contained numerous genera representing specimens from Chlorophyta, Euglenophyta, Bacillariophyceae, and Cyanobacteria
Cell density of Microcystis aeruginosa increased for each treatment during the course of the 15-day experiment and there was no M. aeruginosa observed in the control group during either experiment runs

Summary

Introduction

Rapid growth and acceleration of phytoplankton biomass, usually associated with eutrophication, is commonly termed as an algal bloom [1] [2]. Algal blooms can reduce nutrients, decrease the photic zone, and deplete dissolved oxygen causing hypoxia or anoxia [4] [5], creating an environment that is not suitable for surrounding biota These blooms form unsightly scums in surface water, reducing the aesthetic and recreational value of effected systems. Cyanobacteria have unique adaptations given their long evolutionary history including the ability to take up phosphorous in excess and store it for use in conditions where phosphorous is limited [6] These unique adaptations allow cyanobacteria to proliferate in nutrient enriched and nutrient deficient conditions making them the most common nuisance alga in freshwater systems worldwide [1]. Given their long evolutionary history, production of toxins by cyanobacteria predated any possible grazers and some of these toxins are thought to be involved in a protective role in the oxidative stress response of cyanobacteria [7]

Methods

Results

Discussion

Conclusion