Phytoplankton are microscopic plant-like organisms that live in the water. Their name tells us that they live on light (phyto) and drift with the water (plankton). Every drop of water normally contains hundreds of thousands of these tiny, single-celled organisms. Phytoplankton are natural and important; they produce 50% of the oxygen in the air we breathe, and they are also food for fish and other animals in the ocean. There are many hundreds of different types of phytoplankton. For decades, most scientists have thought that phytoplankton lived only by photosynthesis. It turns out that many of these phytoplankton also eat the way animals do. Some eat other phytoplankton, some eat bacteria, and some eat tiny animals. Some of these mixotroph phytoplankton eat only reluctantly or rarely. Some are aggressive and can stuff themselves full of food! These mixotrophs grow much faster when they can eat and photosynthesize at the same time, compared with when they grow by photosynthesis alone.
The ways the mixotrophic phytoplankton eat can be pretty gruesome. Some gobble up entire organisms, while some harpoon their food and suck out the innards using a self-made straw.

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