BWB – Swimming through a forest

The brave souls who venture into the cold waters of a temperate rocky shore of all our oceans, might dive into one of the most spectacular marine ecosystems, the kelp forests. In these cold and nutrient rich waters huge forests made out of kelp grow, truly a spectacular sight to be seen. Kelp is the colloquial name for several large brown algae species, belonging to different genera like Laminaria, Ecklonia and Macrocystis. These algae can reach sizes of up to 30m in some places, comparable to the sizes of trees like oaks, pines or birches. In contrast to these trees though, kelp grows fast (some species up to 30-40cm a day). Kelp consists of three mayor structures, the leave like fronts, the stem like thallus and the root like holdfasts. The kelp stays vertically in the water with the help of gas-filled bladders attached to the thallus or fronts. Nutrients are taken up through the fronts and to a lesser degree through the thallus. 

Like in a forest on land, a kelp forest consists of several layers. At the surface we have the canopy made up by the kelp fronts of the full grown kelp. Diving deeper we get to the understory layer. Here we have younger kelp and other algae growing in a shaded environment. The last important layer is at the bottom the substrate. Here the kelp is attached via the holdfasts to the substrate but also many other organisms can be found there. All of these layers provide habitat for a huge diversity of organisms, some living even on the kelp itself. This biodiversity includes several species of fish, sharks, seals, crabs, nudibranchs, penguins, sea urchins, sea otters, sea anemone and many, many more.

But kelp forests are not only important for this biodiversity. They provide several ecosystem services to us humans too, from which we profit. For example many commercially fished species, fish and invertebrates, spend some part or their whole life in kelp forests. Also some species of kelps are being eaten by us humans directly, are processed into fertilisers or substances are extracted for the food and cosmetic industry. A part from these direct uses, kelp protects the coast from erosion by mitigating the impact of waves and storms on the shoreline, preserving with that our beautiful coast and beaches.

So next time you are at the rocky coast for example in Cape Town (South Africa), California (USA), Tasmania (Australia), northern Portugal or Brittany (France) take a dip under the surface or if you find washed up kelp at the beach, think about this amazing ecosystem below the waves.

By Horst Schulte