An electron microscope study of a natural population of picoplankton from the Celtic Sea

Abstract

Water samples from the Celtic Sea have been concentrated and examined by scanning and transmission electron microscopy. Cyanobacteria were abundant and had maximum cell dimensions ranging from 0.5 to 1.0 urn. In addition to these prokaryotic cells, numerous eukaryotic algae were present which had maximum cell dimensions only slightly larger (0.85 to 2 pn) than the cyanobacteria; these eukaryotic cells were 'Chlorella-like' green algae, possessing neither scales nor flagella. Many of these eukaryotic algae and all of the cyanobacteria would pass through a 1 pn pore-size sieve and were the organisms responsible for the high rates of primary production by picoplankton in the Celtic Sea.