Microcystis exposure decreases walleye egg hatch success

Session: Harmful Algal Blooms: From Ecosystem Drivers to Ecosystem Impacts (4)

Ali Shakoor, Wayne State University, [email protected]
Donna Kashian, Wayne State University, [email protected]

Abstract

In recent years, harmful algal blooms (HABs) are occurring with increased frequency, duration, and intensity.  In the Western Basin of Lake Erie, Microcystis is the most common HABs-forming cyanobacteria. Microcystis toxins have wide-ranging adverse effects on fish. However, the impact of HABs on Great Lakes fisheries, specifically walleye, is poorly understood.  The objective of this study was to determine the impacts of Microcystis ichthyoblabe exposure on fertilized walleye egg survival and hatch success.  Fertilized eggs were exposed to river water (control), M. ichthyoblabe, and Ankistrodesmus falcatus, a non-toxin producing green algae.  The algae treatments had two levels: 4x10⁴cells/mL, recognized as the minimum threshold for severe HABs events on Lake Erie, and a lower concentration of 1x10⁴cells/ml. Microcystis ichthyoblabe exposure had no effect on egg survival. However, both concentrations of M. ichthyoblabe reduced hatch success by approximately 50% when compared to all other treatments, while the lower concentration of M. ichthyoblabe further reduced hatch success when compared to its higher concentration. Understanding how early life-history stages of walleye interact with stressors, such as HABs, may lead to a better understanding of how HABs events may affect walleye populations, thereby providing valuable information for improved ecosystem-based fishery management.