COS 152-1 - Recovery of zooplankton communities following whole-lake disturbance

Thursday, August 10, 2017: 1:30 PM
B112, Oregon Convention Center
Brian N. McGann, Environmental Science and Management, Portland State University, Portland, OR and Angela L. Strecker, Environmental Science & Management, Portland State University, Portland, OR

Community assembly following disturbance is a key process in determining the composition and function of the future community. However, replicated studies of community assembly at whole ecosystem scales are rare. Here, we describe a series of whole-lake experiments in which the recovery of zooplankton communities is tracked following an ecosystem-scale disturbance. Fourteen lakes in eastern Washington were chosen: seven lakes were treated with rotenone, while the remaining seven were controls. Each lake was monitored six months before and one to two years after the rotenone treatments. Zooplankton tows were taken monthly, at a shallow, intermediate, and deep site in each lake, and were later enumerated and identified. A depth profile of environmental variables was taken at the deepest site. Landscape factors were also characterized including surrounding geology, vegetation type and distance to nearby lakes. Community responses following disturbance were assessed using NMDS and relative importance of environmental variables was compared. Communities were considered recovered if there was no significant difference between treatment and control in zooplankton community metrics of abundance, richness, composition, and diversity.


There was a steep decline in the abundance, richness, and diversity of the zooplankton community post-treatment. In many of the lakes, Cyclopoid copepods were the first group to recover, remained dominant for a few months, and may have exhibited priority effects advantages. Calanoid copepods were the slowest group to recover. There were varying recovery times between lakes. These findings suggest that lake zooplankton communities primarily respond to intense short-term disturbance through emergence of diapaused stages from the sediment. This sediment emergence is dependent upon a range of abiotic and biotic factors, which can help predict the re-establishment time of communities. Results of this study may give insight to disturbance ecology and the relative importance of founding versus colonizing processes.