Kelp forests are a type of marine ecosystem established around colonies of kelp; they contain rich biodiversity. Kelp can stretch up to 50 feet (15 meters) or more from their anchors on the sea floor to the surface, providing a vertical infrastructure that is home to many fish and invertebrate species. Kelp forests also often attract mammalian visitors, including whales, sea lions, sea otters, and SCUBA-diving humans.

Kelp forests draw their name from an analogy to forests on land.

Environmental Characteristics

Kelp forests are found in temperate ocean waters around the globe wherever water conditions are conducive to the successful establishment of kelp colonies.

Kelp favors waters below about 68 degrees Fahrenheit (20 degrees Celsius); various species of kelp favor different ranges of temperatures under this limit, but none grow in waters where the temperature is consistently warmer. Relatively clear water is also necessary, as kelp depends on photosynthesis.

Kelp forests are typically found in waters between 20-80 feet (6-24 meters). Water clarity is a key factor determining the depth of water a kelp forest can thrive in, as sufficient light must reach the depth where kelp are anchored to the sea floor and first start to grow.

A high nutrient content (for example at an upwelling), moderate water movement via wave action or current, and a hard base for attachment are also all necessary requirements for the establishment of a kelp forest.

Major kelp forests can be found in both the Northern and Southern hemispheres, along the coasts of west North America (from southern California to Alaska), South Africa, southern Australia, and the west coast of South America.

Kelp

This section explores the characteristics of kelp as it affects the kelp forest as an ecosystem. For more information on the organisms classified as kelp, see kelp.

Physiology

The general morphology of various kelp species form the basis around which the kelp forest ecosystem is built. Kelp have three basic structural units:

• The holdfast is a root-like tangle which fixes a kelp to the sea floor or other anchoring surface.
• The stipe is a long stender stalk which extends vertically from the holdfast toward the surface.
• The fronds are leaf-like attachments to the stipe, are very numerous, and are the major sites of photosynthetic activity.

In addition, many kelps have pneumatocysts, or air bladders, located along the stipe or at the base of fronds, to help the kelp maintain a roughly vertical posture.

Kelp usually grows to the surface, and may continue to grow in length after reaching the surface, causing a canopy of floating fronds to develop. This dense vertical infrastructure with overlying canopy forms a system of microenvironments similar to those observed in a terrestrial forest, with a sunny canopy region, a partially shaded middle, and darkened floor. Each of these regions provides different niches for many types of animals and other plants.

Growth cycle

Kelp grows extraordinarily quickly. In the proper conditions, Giant kelp (genus Macrocystis ) can grow vertically 12 inches (30-60 centimeters) per day. Therefore, kelp forests rapidly reach a "mature" status, in striking contrast to terrestrial forests which may take hundreds of years to mature (see old growth forest).

Some kelp species live for only one year (analogous to annual terrestrial plants), while others thrive for up to seven years (corresponding to perennial plants). In perennial kelp forests, it is common to see the highest growth rates during the spring and summer months, with a corresponding die-back during the winter. Winter storms can also affect the growth cycle of kelp by tearing holes in the canopy, pruning fronds from kelp, or even dislodging entire kelp plants from the sea floor. This helps sunlight filter down to lower depths and creates gaps where new kelp plants can establish themselves.

Microenvironments

Kelp Forest

Inhabitants and visitors

Vertebrate aquatic animals

Invertebrate animals

Plants and algae

Semi-aquatic animals

References

Kelp Watch Monterey Bay Aquarium Kelp Forest Exhibit information

External links

• Monterey Bay Aquarium Kelp Cam - watch a live feed from the Monterey Bay Aquarium's kelp forest exhibit
• Kelp Watch - a project by the Department of Primary Industries, Water & Environment of the government of Tasmania, Australia, with excellent general information on kelp forests as well as specific information on Tasmanian kelp forests.