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Kelp forests – Underwater forests | KnowledgeisKey


>Kelp forests are underwater ecosystems that form in shallow waters by the dense growth of several different species known as kelps. Kelp forests can develop at incredible speeds, once barren areas can quickly become thriving forests, growing to height of 2-30 meters. Kelp forests are inhabited by a huge variety of marine animals.

By, Ricky Goacher | Date: 04/12/2017

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Fun Facts:

Sea kelp is one of the fastest-growing plants (extremely large, brown algae seaweed) on the entire planet.

Giant kelp

Although kelp may look like a plant, they are actually extremely large, brown algae seaweeds (order Laminariales) that live in cool, relatively shallow waters of rocky coastlines, strapped to the ocean floor with their root-like holdfast. Kelp grow in dense groupings - much like you would see in a forest on land. These forests provide food and shelter for thousands of fish, invertebrates, and marine mammal species, as well as providing a unique three-dimensional environment in our oceans.

Kelp morphology

Giant kelp morphology diagram

Kelp morphology is simple and much like that of a plant, they comprise of:

  • A root-like holdfasts, which is used to strap the kelp down to the rocky coastlines. However, unlike any other plants roots, these holdfasts are not used for the absorption of nutrients - but are primarily used to anchor the kelp to the ocean floor.

  • A stipe - resembles the stem of a plant, with blades acting as leaves. Attached to the stipe and blades is the unique float that holds up the kelp.

  • The most interesting part of the kelp's morphology, has to be their unique floats, or pneumocysts, attached to the ends of the blades. These pneumocysts are gas filled compartments which help the blades reach the light closer to the surface.

  • Fronds – Leaf-like blades that serve an important role for the kelp, and are entrusted with both photosynthesis, and mineral absorption. Blades are also used by many organisms as a cover to hide their young, or even as a shelter from storms.

Some kelp species, like giant kelp, can grow at an exponential rate. When in ideal conditions some kelp can grow up to 18inches in one day! To put this in perspective, just imagine how long it would take a plant to reach the same dimensions.

Once classified as plants, thanks to new genomic information, kelp has been re-classified and now belongs to the Phaophyta, or brown algae, in the kingdom of chromists. This new classification is due to the chromists having their own characteristics, with unique biochemistry that cannot be found in plants. For example - like plants, chromists use chlorophyll (a) in photosynthesis, but what makes them different is the use of chlorophyll (c), which is a pigment based on fucoxanthin, most efficient at utilising the blue-green light that penetrates the ocean.

What does kelp need to grow?

Sea weed and kelp

The ideal habitat for kelp's growth is nutrient-rich clear waters, with temperatures between 42-72 degrees Fahrenheit (5-20 degrees Celsius). If these conditions are met, and the sunlight is able to reach the ocean floor, the kelp will begin to develop. Anchoring to the sea bed, the kelp will rapidly grow, however, a number factors can slow the rates of growth, these include and aren't limited to, temperature – if the water temperature reaches above 20 degrees, the kelp is known to suffer; storms – it can rip the kelp away from the ocean floor; and pests – numerous marine animals, such as sea urchins and snails, consume kelp as part of their diet.

What lives in a kelp forest?


Numerous invertebrates inhabit kelp forests, the most common of these invertebrates are:

Red sea urchin
  • Bristle worms
  • Scud
  • Prawn
  • Snails
  • Brittle stars.
  • Sea stars
  • Anemones
  • Crabs
  • Jellyfish
  • Sea urchins


Fish also reside and seek the safety of kelp forests, and use them as nurseries. Common fish found in kelp forests are:

Leopard shark in kelp
  • Black rockfish
  • Blue rockfish
  • Olive rockfish
  • Kelp rockfish
  • Garibaldi fish
  • Leopard sharks
  • Giant sea bass

Marine mammals

Marine mammals use the kelp forests for a variety of reasons, like food, shelter from storms and protection from predators. Common marine mammals are:

Sea otter floating in the ocean
  • Sea lions
  • Seals
  • Grey whales
  • Sea otter

Why are sea otters important?

Sea otters are incredibly important to the oceans kelp forests, without them, there probably wouldn't be any kelp forests. Sea urchins – small, spikey invertebrates which live on a diet of vegetation. Sea urchins have the ability to swarm in massive numbers, decimating plant life on their path.

The urchins eat away at the kelp's holdfasts, which is a big problem, as they can turn a once thriving kelp forest into a barren wasteland.

Sea otters are vital for maintaining kelp forests because the feed on red sea urchins, which normally would continue to multiply, eating the forest away and leaving nothing behind. Due to large numbers of sea otters being hunted for their fur, huge areas of kelp forests where destroyed, however, protection has been given to these adorable creatures and their numbers are on the rise along side the kelp.

Kelp forest distribution:

Kelp forest distribution map


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