Tag Archives: Holdfast

Kelp Rafts

Kelp is anchored in the ocean by a root-like structure called a holdfast. During storms, or when large waves or strong currents come through, kelp can detach from its underlying substrate and begin to drift in the ocean. As the kelp floats along it often becomes entangled and forms a buoyant configuration of algae that we refer to as a kelp raft, or kelp paddy. While still anchored, kelp provides protection for fish and a is a habitat for many invertebrates such as snails, sea stars, and crabs. After the organism is uprooted, kelp rafts attract many new species adrift, while original dwellers often continue to call it home.

kelpAs kelp rafts drift into the open ocean, they become an important resource for pelagic species of fish. Living in the open ocean, these fish can take advantage of the kelp raft as a possible food source where invertebrates and high densities of plankton may be trapped. Baitfish often school under kelp rafts for protection, and clusters of juvenile fish use this drifting habitat as a nursery. Even our largest bony fish, the mola mola, or ocean sunfish, will come to the surface where a kelp raft is present to solicit the help of cleaner fish and birds that are looking for a tasty meal to rid the massive fish of its parasites.

These rafts can drift for miles across the ocean, and have even been regarded as a way for marine invertebrates and different species of algae to find new homes on nearby islands or drift to different countries. You never know what types of animals you will find in or under a kelp raft, so take a peak next time and see who made this floating ecosystem its home!

Written by: Jaclyn Lucas

Holdfast: The Anchor of Algae

Kelp and algae are like the trees and shrubs of the aquatic world except for one important factor, THEY’RE NOT PLANTS!  Kelp is in fact in the Kingdom Protista meaning that among other things it does not use roots to absorb nutrients nor does it have a vascular system to transport those nutrients to its various structures. The part of kelp most similar in appearance and location to the roots of plants is called the holdfast. This spaghetti like structure has a primary function of securing the organism to the sea floor; holding it “fast” in all but the most turbulent conditions.

Close Up

Because of the way kelp holdfasts are tangled and tasseled, they make the perfect protected place for young ocean animals to get their start in the world. If you were to find an uprooted holdfast floating at sea or on the beach you would be likely to spot more than a few species of animals. Everything from brittle stars to isopods to tube worms, tiny sea hares, kelp crabs and baby octopus can be found in these miniature nurseries. Scientists believe you could find over one hundred species in a single holdfast!

Some holdfasts like those of the giant brown kelp are expansive and winding while others, like that of the sea palm, are more puck-like and perfectly adapted to cement firmly onto rocks and other hard substrate. This tight grip allows kelp to stay stationary for a long time.  While the blades of kelp only live about a month or two, holdfasts can live and grow for up to ten years or more!

More information on kelp and holdfasts can be found at this link: Additional Kelp and Holdfast Information

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