bioluminescence Emission of visible light by living organisms. chlorophyll Any of a group of related green pigments found in photosynthetic organisms. ciliate Any of various protozoans of the class Ciliata; having numerous hairlike projections that extend from a cell surface that are often capable of rhythmical motion. consumer Primary consumers are organisms that consume plants. Secondary consumers are organisms that consume animals. cytoplasm Protoplasm outside a cell nucleus. decomposer Organism that breaks down dead organic material to inorganic forms. ecosystem An ecological unit composed of the non-living environment and communities of organisms, found living in a large geographic area. eukaryotic An organism having one or more cells with well-defined nuclei. flagellum One of the whiplike extensions of certain cells or unicellular organisms, commonly used for locomotion (plural: flagella). flow cytometry The technique of measuring optical properties of individual cells, or particles in general, in a flow stream rapidly passing one-at-a-time in front of a laser beam with detectors measuring fluorescence and light scatter. A flow cytometer can measure these parameters at rates of thousands of cells per minute. fluorescence Occurs when matter absorbs light then emits light at a longer wavelength. micrometer One millionth of a meter. An average human hair is about 50 micrometers wide. Click here to learn more about the relative sizes of marine plankton nauplii Early egg-shaped larval stage of copepods and other crustaceans. Nauplii are unsegmented and bear three pairs of appendages. nucleus A complex, usually spherical protoplasmic body within a living cell that contains the cell's hereditary material and controls its metabolism, growth and reproduction. nutrients Any of a number of inorganic or organic carbon-based compounds used primarily in the nutrition of plants; e.g., nitrogen and phosphorus compounds. ocean color Ocean color is determined by the interactions of incident light with substances or particles in water, usually phytoplankton and inorganic particulates. photosynthesis The process whereby plants utilize carbon dioxide, water, and solar energy to manufacture energy-rich organic compounds, accompanied by the release of oxygen. pigment A susbstance that imparts a characteristic color to plant or animal tissue (e.g., chlorophyll, hemoglobin). plankton Generally microscopic organisms that float or drift in water. primary productivity The mass of organisms produced through photosynthesis per unit area and time by plants (i.e., primary producers). Click here learn more about primary productivity. producer Plants are primary producers. trophic Position in the food chain, determined by the number of energy transfer steps to that level