The objective of this research was to identify the materials and
methods necessary to study the attached algal community on a
river bottom in deep water. The study site was the Susquehanna
River near Falls, Pennsylvania . Artificial substrates of smooth
glass, frosted glass, Vermont slate, `sandy slate' (flagstone) and
acrylic plate were placed on the stream bottom in detritus free
sample holders by scuba divers. Both monthly and long-term
cumulative samples were collected from the plates employing
scuba and a Bar-Clamp sampler . River stones (natural substrates)
were collected for comparison . Samples were analyzed
in a Palmer Cell under a Bausch and Lomb research microscope .
Diatoms were the most important colonizers of river stones, with
the genera Nitzschia and Navicula most abundant . Highest
periphyton densities occurred on natural substrates in winter
with a maximum of 2 .2 x 10° units/ mm 2 . Artificial substrates
with one month exposure periods accumulated maximum
periphyton density from May through October with relatively
low densities in winter . Cumulative artificial substrates were
most like river stones in patterns of colonization . Frosted acrylic
is recommended for future studies employing benthic artificial
periphyton substrates .
Introduction