Tag Archives: Kelp

Kelp: The Floating Forests

What has the world’s fastest linear growth, contains remedies for everything from heartburn to wrinkles, and might be in your t-shirt right now and in the PB&J you had for lunch?

If you said giant brown kelp, Macrocystis pyrifera, you’re right!

Tree of life
Algae is different from land plants because it lacks a root system that sucks up water and nutrients from the soil, instead using a root-like system called a holdfast, a cone-shaped network of branches called haptera, to anchor to its substrate. However, its growth is so successful because the more mature blades near the water’s surface can efficiently transfer excess sugars through passageways called sieve tubes down to the younger blades below that cannot yet provide all the energy they need through photosynthesis.

Kelp plantImage from KelpWatch, found at http://www.geol.utas.edu.au/kelpwatch/facts_b.html

Giant brown kelp is part of the phylum Ochrophyta, named for the ochre-colored pigments in its blades (or “lamina”). Instead of chlorophyll, this phylum uses a brown pigment called fucoxanthin in photosynthesis, giving it the brown color that makes it part of the class phaeophyta, the brown algae. Brown algae is the most diverse of the three classes of algae (brown, red, and green) — it comes in all shapes and sizes, and includes the world’s largest algae, like Macrocystis pyrifera!

Sequoia of the sea
Macrocystis pyrifera is the world’s largest seaweed, reaching 50-60 meters in length and 100 kg in weight, with blades up to 70 cm long. In ideal conditions (shallow rocks or coarse sand in cool, nitrogen-rich waters) it can grow 50-60 cm in a single day – that’s almost two feet – and 45 m in a single growing season – that’s as tall as the Statue of Liberty! Giant brown kelp is perennial, which means that it often dies back to its holdfast in winter, losing up to three quarters of its mass before regrowth in warmer season. Kelp can live up to five to eight years, and its massive size has given it the nickname “sequoia of the sea.”

kelp cartoonImage from Tours de Jours comic strip, Catalina Islander, found at MicrobeWiki.Kenyon.edu

Lay it on thick
Alginate, algin, or alginic acid, is a thickener found in many household products that is derived from the cell walls of brown algae. Sodium alginate is the main gum extracted from giant brown kelp, but other forms of this gel-like substance include potassium alginate and calcium alginate.
These products are used in manufacturing paper and fabric, in dyes, for waterproofing and fireproofing, and as a thickener for drinks, ice cream, creamy or gel-like foods (such as jelly or Velveeta cheese) and cosmetics, and even as an alternative wound dressing.

Extract from giant brown kelp, which is rich and vitamins and minerals including iodine, is also taken as a dietary supplement to promote healthy hair, skin, and nails. Rich in vitamins C and E, it has anti-inflammatory and antioxidant properties. It has also been proven to enhance natural collagen and elastin, proteins in skin that keep it firm and strong, and has been proven to reverse sun damage and prevent wrinkles.

A plant in San Diego operated for 76 years and until its closure in 2005 was the largest kelp harvesting facility in the world. Today, M. pyrifera is still harvested by large barges with spinning blades underneath them that act like marine lawnmowers, for these industrial uses as well as feed in abalone aquaculture.

Floating forests
Kelp is a key organism in shallow ecosystems because it provides plentiful food and shelter for otters, urchins, and many sessile invertebrate species. Macrocystis is the most widely distributed genus of kelp in the world, forming large, dense forests from Australia and New Zealand to South Africa all the way up the western coasts of the Americas. A study off San Clemente found that just as in a terrestrial rainforest, giant brown kelp outcompetes smaller understory kelp, opening up ample space for sessile invertebrates on the bottom. Often, the top layers of a kelp canopy will break off to form a kelp raft, a floating community rich in biodiversity. This is key in both the life cycle of the kelp and of its inhabitants, allowing reproductive spores to travel 1,000 km or more to start new colonies. Some small invertebrates even complete an entire life cycle including a planktonic larval phase, adult phase, and new generation before a kelp raft sinks or floats ashore.

To learn more about giant brown kelp, check out the Seaweed Industry Association website or this page in the Encyclopedia of Life. To see some awesome photos of kelp being harvested off the California coast, check out this collection.

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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