Early eutrophication in the lower great lakes:

New Evidence from Biogenic Silica in Sediments New evidence from studies of biogenic silica and diatoms in sediment cores indicates that eutrophication in the lower Great Lakes resulted from nutrient enrichment associated with early settlement and forest clearance. Diatom production peaked from 1820 to 1850 in Lake Ontario, at about 1880 in Lake Erie, but not until 1970 in Lake Michigan. This is the first reported sediment record of the silica-depletion sequence for the Great Lakes.

Eutrophication, silica depletion, and predicted changes in algal quality in lake michigan.

Accelerated eutrophication stimulated by pollution inputs is causing silica depletion in the surface waters of Lake Michigan during summer stagnation. Limitation of the reproduction of the presently dominant phytoplankton organisms, which require silica, may lead to drastic and, on the whole, undesirable changes in the ecosystem.

POLYMORPHISM IN MASTOGLOIA(1).

Cells in a -wild population of a species belonging to the diatom germs Mastogloia may form frustules of 2 strikingly different morphologic types during their vegetative life cycle. Total conversion from coarsely structured morphologic form to a more finely structured form takes place during a single division; hence no inter gradations between the 2 forms are evident. Intact frustules with 1 valve of each type leave no reasonable doubt of the ability to make the change.