Phytoplankton, microscopic plant life found throughout the ocean, are at the bottom of the oceanic food web. Unable to swim against the current, their movements are primarily based upon the ocean currents and wind. So how did these little critters contribute to the coloring of the water? Phytoplankton, like all plants, have chlorophyll. Chlorophyll is a green pigment that plants have to absorb sunlight in order to convert it to energy. Chlorophyll appears green because it reflects back blue to green wavelengths of light. When a phytoplankton bloom, or an abundance of phytoplankton caused by weather conditions occurs, the concentration of chlorophyll in the water causes a blue-green tint.