Phytoplankton are tiny—almost microscopic—but don't let that fool you. These free-floating, plant-like organisms occupy the bottom of the ocean's food chain, making them vital to the ecosystem. They live in the ocean and in sea ice, and like plants on land, phytoplankton need sunlight. Most are buoyant and float in the upper portion of the ocean where sunlight can reach them. They provide food for a wide array of species, like whales, shrimp, snails and jellyfish.

In the Arctic, phytoplankton blooms are triggered by the melting of sea ice in spring. Light green shelves of phytoplankton swirl into the Arctic Ocean. As the climate changes and the oceans warm, the timing of phytoplankton blooms is shifting and the species are showing up in different places altogether. As this happens, the effects ripple outward, growing in significance along the way.

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