TY - JOUR AU - Denis, Michel AU - Martin, Valérie AU - Andersen, Valérie PY - 2000/06/30 Y2 - 2024/03/28 TI - Short-term variations of the vertical distribution of cyanobacteria in the open Mediterranean Sea JF - Scientia Marina JA - Sci. mar. VL - 64 IS - 2 SE - Articles DO - 10.3989/scimar.2000.64n2157 UR - https://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/752 SP - 157-163 AB - A general study of biogeochemical processes (DYNAPROC cruise, May 1995) was conducted at a station in the open northwestern Mediterranean Sea where horizontal advection was weak. During this experiment, short-term variations of the vertical distribution of cyanobacteria were investigated and a possible link with diel vertical migration was considered. Consistently, the experimental work was conducted at a time scale of a few hours. Cyanobacteria were the most abundant population in the pico- and nanoplankton size-class. Their vertical distribution was monitored over 36 h with a frequency of 4 h. With such a time resolution, they experienced a single grazing event during daytime and, at night, they were heavily grazed when the upper layers were occupied by organisms migrating from the aphotic zone. The corresponding integrated (0-90 m) losses of cyanobacteria during the night amounted to 534 mg C m<sup>-2</sup>. Though daytime grazing is most likely due to nanoflagellates and microzooplankton, night-time grazing could significantly involve migrant macrozooplankton organisms and sustain a periodic export of organic matter. This study stresses the importance of the potential export of organic matter as a consequence of the diel vertical migration, export that could not be accounted for by measurements at longer time scale. ER -