Underwater forests formed by dense stands of large brown algae, most famously giant kelp, which anchors to the seafloor and grows toward the surface at rates that can exceed half a meter a day, among the fastest growth of any organism on Earth. Found along cold, nutrient rich coastlines on every continent but Antarctica, from the Pacific coast of North America to the shores of South Africa, Australia and Chile, kelp forests rank among the most productive ecosystems on the planet, sheltering fish, invertebrates and marine mammals within their canopy. The system depends on a delicate balance of predators and grazers, most famously sea otters, whose decline can let sea urchin populations explode and strip a kelp forest down to bare rock, a collapsed state known as an urchin barren.
Facts
Disputed
Area (sq km)The Kelp Forest Alliance report states the true global extent is currently unresolved: observed estimates run about 50,000 to 100,000 square kilometers (5 to 10 million hectares) while modelled estimates run far higher, up to about 1,500,000 square kilometers (150 million hectares). The lower, directly observed figure is recorded here rather than a modelled upper bound. Connections
Demonstrates
Kelp forests depend on current-driven coastal upwelling, such as the California Current system, to deliver the cold, nutrient-rich water kelp needs to grow at the rates that build a forest canopy.
Source National Oceanic and Atmospheric Administration
Source National Oceanic and Atmospheric Administration
Hosts
Source Sea Otter (Monterey Bay Aquarium)
In Biome
Marine, Biomes Source National Oceanic and Atmospheric Administration
Open Questions
Source National Oceanic and Atmospheric Administration
Sources
1. Kelp Distribution, Methods Appendix (Kelp Forest Alliance)
Kelp Forest AllianceSection 7.0, Kelp Distribution, Methods AppendixQuote, Section 7.0, Kelp Distribution, Methods Appendix
Kelp forests are found in 25 countries across all continents, but the actual area occupied by kelp forest ecosystems is currently unresolved, with observed estimates ranging from 5 M ha to modelled estimates of 150 M ha.
National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administrationsanctuaries.noaa.gov/visit/ecosystems/kelpdesc.html, What is kelp? section
Kelp are large brown algae, not plants, that grow in cool, nutrient-rich coastal waters. There are about 30 different species of kelp worldwide.
- Demonstrates: Photosynthesis
- In Biome: Marine
- Demonstrates: Ocean Currents
View the Source Sea Otter (Monterey Bay Aquarium)
Open Questions (1 open question)
How much of the ocean does kelp forest actually cover?
Kelp beds grow along narrow, scattered stretches of cold, rocky coastline worldwide, many of them remote or difficult to survey by boat, so no single comprehensive census exists; published global-extent estimates vary by more than an order of magnitude depending on the survey method (aerial, boat-based or satellite) and the definition of kelp forest used.
What would resolve this A standardized, repeated satellite remote-sensing survey of the world coastline, cross-validated against in-water surveys, of the kind marine ecologists have begun assembling only in the last few years for select regions.
Marine ecology and remote sensingNational Oceanic and Atmospheric Administration
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