Cyanobacteria (also known as blue-green algae) are on the rise in the U.S. and worldwide, becoming a serious threat to freshwater resources and public health because of their toxins and disruptive effects on ecosystems. Ongoing research funded by the National Center for Coastal Ocean Science is uncovering the secrets of why cyanobacteria are so successful.
Recent experimental research funded under the NCCOS ECOHAB Program in Lake Erie is showing that feeding of larger zooplankton on phytoplankton (microscopic algae and cyanobacteria) is inhibited by the presence of cyanobacterial blooms. One likely mechanism for this inhibition is the cyanobacteria's large colonies and filaments which can interfere with the appendages that mesozoplankton use to harvest food particles from the water. This inhibition of predation is one factor that can promote cyanobacterial blooms.
Smaller size freshwater zooplankton, such as protozoa and rotifers, on the other hand, have been shown by this research to be quite efficient at consuming the cyanobacteria and could potentially control their populations and prevent blooms. However, the research also shows that with high levels of nutrients, cyanobacteria can grow faster than other phytoplankton and at a rate that exceeds the predation rate, even by the smaller zooplankton.
Therefore, this project shows the potential of smaller size zooplankton to biologically control toxic cyanobacteria blooms by grazing. However, without additional control of nutrient pollution entering Lake Erie the blooms will likely outpace zooplankton predation and become more common.
Read the research article: Davis, T. W., F. Koch, M. A. Marcoval, S. W. Wilhelm and C. J. Gobler. 2012. Mesozooplankton and Microzooplankton Grazing During Cyanobacterial Blooms in the Western Basin of Lake Erie. Harmful Algae 15: 26-35.