Diatoms abound in ice-covered Lake Erie: An investigation of offshore winter limnology in Lake Erie over the period 2007 to 2010

The limnology of offshore Lake Erie during periods of extensive (>70%) ice cover was examined from ship borne sampling efforts in 2007 to 2010, inclusive. Dense and discrete accumulations of the centric filamentous diatom Aulacoseria islandica (>10 mu g Chl-a/L) were located in the isothermal (<1 degrees C) water column directly below the ice and only detectable in the ship wake; viable phytoplankton were also observed within ice. Evidence from these surveys supports the notions that winter blooms of diatoms occur annually prior to the onset of ice cover and that the phytoplankton from these blooms are maintained in the surface waters of Lake Erie and reduce silicate concentrations in the lake prior to spring. The mechanisms by which high phytoplankton biomass rise at this time of year requires further investigation, but these winter blooms probably have consequences for summer hypoxia and how the lake responds to climate change. (C) 2012 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.