KELP

Blue Forests Basics

What are Kelp forests?

Kelp are large, brown algae seaweeds that are found in the shallow outer region of coastal zones. In Norway, the most common kelp species present are in the Laminaria genus, including oarweed (Laminaria digitata), tangle kelp (Laminaria hyperborea), and sugar kelp (Laminaria saccharina). Winged kelp (Alaria esculenta) and furbellow kelp (Saccorhiza polyschides) are also found domestically, though these have shorter lifespans of just one year.

Tangle and sugar kelp constitute the largest biomass of permanent algae in Norway, and they form large kelp forests along the coast. The kelp in Norway can grow up to four meters high. Kelp do not reproduce by seeds and pollination like terrestrial plants do, but instead they contain microscopic spores. These spores are released, then they attach to the seabed and grow into male and female plants. When the male plant has fertilised the female plant, new spores are released. Other species of kelp can multiply by parts of the blade breaking off and attaching to the seabed to grow a new individual.

Kelp grow similarly to trees in a forest by creating 3-dimensional structures underwater that provide unique habitats, refuges, and nurseries for diverse groups of marine organisms.

WHERE ARE KELP FORESTS FOUND?

Kelp forests grow in shallow, rocky habitats in most temperate coastal areas in northern latitudes of the world. They cover 25% of the world’s coastline and much of the Norwegian coast. Norwegian kelp forests in particular make up a large part of the total areas of blue forests in Europe.

Unlike plants, macroalgae do not have roots. Instead, they have holdfasts that are used to attach to rocks and other hard substrate. Kelp do not grow further than where the sun’s rays reach because they photosynthesise. Therefore, kelp thrive best when growing from 1 to 25 meters deep, which is slightly deeper than rockweed. In terms of wave energy, some species like tangle kelp can tolerate stronger waves, whereas sugar kelp prefer calmer waters.

WHAT BENEFITS DO KELP FORESTS PROVIDE?

Kelp forests form the basis of life for many marine species. Smaller algae often grow on kelp stalks and their underbrush, especially red algae. In addition to the algae, small crustaceans and molluscs thrive particularly well, as do fish who seek refuge within this blue forest. Molluscs, crustaceans and small fish also serve as food sources for larger animals such as seabirds, marine mammals, and larger fish. Thus, many species are drawn to this unique and diverse ecosystem.

Though kelp do not have roots, they still can capture carbon. Living kelp are considered short-term carbon sinks through the biomass they produce. This biomass is either eaten by other animals, or it breaks off to form detritus, which often drifts far from its original location before settling onto the seabed. Unlike living kelp, kelp detritus sequesters carbon for centuries once it becomes buried in seafloor sediment.

When harvested, kelp also provide other commodifiable provisioning services. Kelp can be transformed into thickening agents, cosmetics, medical dressings and supplements, plastic alternatives, edible products, and animal feed.

What are Kelp forests threatened by?

Some kelp species are very sensitive to increases in water temperature. There has been a large decline in the distribution of sugar kelp in southern parts of Norway in recent years, which may be due to heat waves increasing ocean temperatures.

In northern Norway, the biggest threat to kelp forests has been the grazing of sea urchins. The sea urchin eats the entire kelp, leaving large areas of kelp forest deserted. This can be detrimental to an entire ecosystem, and therefore affects several fish species. Sea urchins can survive for extended periods of time without receiving nutrition from the waters above. Even if the kelp in an area have been eaten, the sea urchins often remain. With so few predators – namely crabs and large fish – and excellent conditions for the sea urchin, kelp forest populations have been in decline in Norway. Researchers have been working for several years on a possible solution to the grazing problem in northern Norway. However, the larvae of the sea urchins are not particularly heat-tolerant, so it appears that some kelp species may benefit from increased sea temperatures.