Cytoplasmic streaming. Timelapse differential interference contrast microscopy of cytoplasmic streaming, or cyclosis, in the marine dinoflagellate Pyrocystis fusiformis. Chloroplasts, the site of photosynthesis, are green. Also seen are scintillons, bioluminescent particles found in the cytoplasm. Dinoflagellates are unicellular protozoans. About 90 are found in marine environments as plankton. P. fusiformis is bioluminescent at night, when the movement of tides, storms and passing ships cause them to emit short flashes of light.