Natural benthic substrates were collected beneath the ice of Grand Traverse Bay by divers on March 10, 1978 as part of a seasonal investigation of northern Lake Michigan benthic algae assemblages. Some of the samples from each selected depth between the surface and 32 m were examined used SEM. Natural substrates (silt, sand, pebbles, algae, shells) were field-fixed in glutaraldehyde, dehydrated, and critical point dried. Samples were sputter coated and examined with a Hitachi HHS-2R SEM operating at 20 kV.