Phytoplankton nycthemeral behavior off Callao (12°S), Perú

Abstract

Between April 18th to 21th of 2006, nycthemeral behavior changes in phytoplankton were studied at two stations off the central coast of Peru (12°S). Water samples were collected every 6 hours to a depth of 75 m. Phytoplankton composition and abundance were determined in relation to dissolved oxygen. Differences in the nycthemeral fluctuations are discussed, focusing mainly in the vertical distribution of the diatom Asterionellopsis glacialis, the dinoflagellate Akashiwo sanguinea, and phytoflagellates at the closest coastal station. The first two species reached 25 m in depth during the night; whereas the phytoflagellates showed highest abundances in the Oxygen Minimum Zone at both day and night times in the station located at 30 nm.