Photosynthesis process featuring its light and dark stages

WHOI biologist Sam Laney studies the daily lives of single-celled plants in the ocean known as phytoplankton. The organisms carry out photosynthesis within specialized organelles called chloroplasts, which contain the green pigment chlorophyll. The chloroplasts act like little factories, taking in raw materials (carbon dioxide) and energy (sunlight) to create products (sugars) but too much light energy on bright days can damange chlorophyll, and too little on cloudy days doesn’t provide enough energy. To cope, phytoplankton have accessory pigments called xanthophylls that act as gatekeepers. (Illustration by Katherine S. Joyce, © Woods Hole Oceanographic Institution)