Skip to main content Skip to navigation

Interactive effects of nutrients and grazing on the control of cyanobacteria blooms across a eutrophication gradient in Washington lakes

Principal Investigators: Gretchen Rollwagen-Bollens, Stephen Bollens
Student: Vanessa Rose
Funded by: State of Washington Water Research Center, USGS
Award period: 2014-2016

Project Summary:

In this project our overall goals were to better understand the interactive effects of nutrient availability and zooplankton grazing on cyanobacteria bloom dynamics in Washington freshwater lakes and reservoirs across a gradient of eutrophication, and to share our results and interpretations with resource managers to better inform decision-making on steps to prevent and/or mitigate freshwater cyanobacteria blooms in the state.

We focused our research on four lakes/reservoirs in Washington state that represent a range of trophic state, from highly to moderately eutrophic (Vancouver Lake and Lacamas Lake) to more oligotrophic (Lake Merwin and Cle Elum Lake).

Our objectives for achieving the project goals were as follows:

      Objective 1: Conduct cyanobacterial/algal growth experiments three times over the bloom cycle in each of four lakes/reservoirs along a gradient of eutrophication, using natural unfiltered water collected from each lake in a 2×2 factorial design.

      Objective 2: Measure a suite of water quality variables (e.g., nutrients, temperature, dissolved oxygen, etc.) in each lake/reservoir.

      Objective 3: Conduct multivariate statistical analyses of field data to assess the relative importance of bottom-up (nutrient availability) and top-down (grazing) factors in influencing cyanobacteria abundance and composition.

      Objective 4: Combine the experimental results (objective 1) with the field results (objectives 2 and 3) to develop predictions of how increased eutrophication will likely impact lakes that currently experience cyanobacteria blooms and those that as yet do not suffer from these blooms.

Publications/Presentations resulting from this project:

Rose+ V, Rollwagen-Bollens G, Bollens S.  (2017)  Interactive effects of phosphorus and zooplankton grazing on harmful algal blooms in a shallow temperate lake.  Hydrobiologia 788: 345-359.