Giant Kelp

Macrocystis pyrifera

Giant kelp is the fastest-growing multicellular organism on Earth, capable of surging upward by up to 2 feet (60 cm) in a single day under ideal conditions.

Scientific name

Macrocystis pyrifera

Taxonomy

Chromista › Ochrophyta › Phaeophyceae › Laminariales › Laminariaceae › Macrocystis

IUCN Red List status

Least Concern

Population trend

decreasing

Biome

aquatic

Habitat

Cold, nutrient-rich temperate marine waters, anchored to rocky reefs at depths of 6 to 30 meters.

Diet

Photoautotrophic (produces energy from sunlight, carbon dioxide, and dissolved marine nutrients).

Range

Eastern Pacific Ocean (Alaska to Baja California), Southern South America, South Africa, Southern Australia, New Zealand

Size

Can reach lengths of 100 to 150 feet (30 to 45 meters) from the seafloor to the ocean surface.

Lifespan

Individual fronds live 6 to 8 months, while the perennial holdfast can survive up to 7 to 10 years.

Active

diurnal

Threats

Ocean warming, marine heatwaves, coastal pollution, and overgrazing by sea urchins due to the decline of natural predators like sea otters.

Safe to approach?

Harmless. When swimming, kayaking, or diving in kelp forests, navigate slowly and calmly to avoid entanglement. If you become caught, do not panic; gently untangle the flexible fronds or slide out of them. It is safe to touch, but do not pull or detach the holdfast from the seafloor.

Macrocystis pyrifera , commonly known as giant kelp or giant bladder kelp , is a species of kelp (large brown algae), and one of four species in the genus Macrocystis . Giant kelp is common along the coast of the eastern Pacific Ocean, from Baja California north to southeast Alaska, and is also found in the southern oceans near South America, South Africa, Australia, and New Zealand. Individual algae may grow to more than 45 metres (150 feet) long...

Photo: Michael Bear, CC-BY, via iNaturalist

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