National Geographic Travelさんのインスタグラム写真 - (National Geographic TravelInstagram)「Photograph by @PaulNicklen | With ivory tusks up to 10 feet long, a pod of male narwhals, known to some as unicorns of the sea, breathe before heading back under the ice to gorge on polar cod. Algae and plankton grow on the underside of the sea ice, copepods and amphipods feed on the plankton, cod feed on the amphipods, narwhals feed on the cod, and polar bears occasionally feed on narwhals. So goes the cycle of life in the Arctic. Ice is like the soil in a garden–without it, all levels of this ecosystem will suffer. Follow me at @PaulNicklen for my favorite picture of narwhals.」6月21日 7時11分