Kelp Forests


Kelp Forests, Bamboes Woude, Amahlathi eKelp

Beautiful, sheltering forests that help provide the air we breathe and food we eat 

Photo: Peter Chadwick

What are Kelp Forests?

Kelp forests are shallow underwater forests made from tall brown seaweeds known as kelp. Kelps are large, fast-growing (up to 13mm a day!) seaweeds that attach to the hard ocean floor using their holdfasts (the base of the seaweed that attaches to the rock) and grow to create a tall canopy stretching to the water surface. Reaching 15m high into the water column, the tall seaweeds create a complex three-dimensional underwater habitat – a jungle that shelters many species. Light filters through the upper canopy of kelp fronds to brighten the diverse forest floor which is home to smaller seaweed and sponge gardens. Kelp forests are as diverse and productive as a tropical rainforest.

Spanning almost half of our coastline, kelp forests occur in patches from the cold West Coast to the temperate South Coast extending more than 30 metres below the water’s surface.  These incredibly productive ecosystems need cold nutrient-rich water to fuel kelp growth and maintain the underwater forest. In the Atlantic Ocean off our West Coast, upwelling systems maintain Kelp Forests, this occurs when cold nutrient-rich water rises from the deeper water to the surface.  On the South Coast, productive kelp systems are maintained by nutrients being brought in seasonally from the west coast and from plant plankton (or phytoplankton) blooms.

Who lives in Kelp Forests?

Healthy kelp forests provide habitats and food for a diversity of different species, many of them endemic – meaning that they are found only in South Africa. There are complex food webs within the forest, maintained by the diversity of animals safeguarded by kelps. 

Kelps are primary producers or autotrophs, meaning that they make their own food by converting sunlight into energy. The main kelp species in South Africa are the giant sea bamboo which has air-filled floats to hold the fronds in the sunlit surface water and the smaller split fan kelp.  Many smaller seaweed species also grow in kelp forests thriving in the sunlit waters. Phytoplankton in the productive waters supports kelp forests, by supplying a much-needed source of food for animals or zooplankton, which in turn feeds many other animals that filter the rich surrounding waters .

Herbivores- animals that eat seaweeds- are the gardeners of the kelp forest. Kelp limpets enable more sunlight to reach the forest floor by feeding on kelp and trimming the algae growing on them. Harvested species like abalone (perlemoen) and snails (alikreukel) creep along in the understory feed on kelp and seaweed, keeping a delicate balance between different components of this undersea jungle. Much of the kelp is broken up by wave action, making a kind of rich kelp soup that animals who remain fixed in one place can feed on by filter-feeding. In kelp forests, filter feeders include sponges, mussels and tubeworms.  Predators and scavengers are key species in Kelp Forests and include sit-and-wait invertebrate predators, opportunistic scavengers as well as active visual predators. Invertebrate hunters include anemones fixed to the seabed and mobile starfish, octopus, rock lobsters and whelks.  Favourite fish from the kelp forest include roman, red stumpnose and Cape bream. Small sharks like pyjama catsharks and leopard cat sharks are common and larger sharks like spotted gully sharks and sevengill cow sharks are also present. Mammal predators include cape fur seals, African penguins, gannets and cape clawless otters.

Why are Kelp Forests important?

Kelp Forests are charismatic ecosystems that benefit people and communities by providing ecosystem services. People have used kelp forests for thousands of years as a place to harvest food. Countless people living near kelp forests still rely on this ecosystem for fishing and harvesting. Many animals living in kelp forests are commercially valuable, like abalone, west coast rock lobster, octopus and fish and kelps themselves have widespread use in food products, fertilizer and pharmaceuticals. (economic value)

Important as a commercial crop, kelps are essential in supporting numerous industries like agriculture, cosmetics and medicine. In agriculture, kelp is important in the production of fertilizer for crops and abalone aquaculture. The alginate extracted from kelp is an important ingredient in beauty products, medicines, soaps, food and has even been used in beer! 

Kelp Forests are SUPER ecosystems. Just like green spaces on land, seaweed forests help reduce and help us cope with climate change. Along with other marine ‘forests’ like mangrove forests, seagrass beds and tidal marshes, kelps are able to remove carbon dioxide from the atmosphere and increase the oxygen content in the water column. Kelp Forests are also able to regulate water temperatures around them creating kelp lagoons where the water temperature is more stable. This helps fish cope with extreme water temperatures and climate change. The tall kelp canopy benefits the surrounding environment and the many species who live within the forest, by reducing rough water, regulating water temperature and increasing the oxygen content in the water column.Kelp Forests are popular places for recreation and support coastal tourism. Investing in healthy kelp forests is an investment in the South African economy as they support coastal businesses and tourism. The Oscar-Winning South African documentary My Octopus Teacher has increased the interest, visitors and appreciation for the Great African Sea Forest.

How do we care for Kelp Forests?

Some kelp forests are protected in Marine Protected Areas (MPAs). In some of these areas, no-take zones allow fish, abalone and lobsters to grow to large sizes and help provide reference areas so we can see what natural kelp forest looks like. As kelp forests are coastal ecosystems, they face threats from both marine and land activities. To care for kelp forests we need to:

Manage fisheries resources and reduce overfishing – Overharvesting threatens many commercially important resources. Overexploitation has severely reduced the population of species key to the way that ecosystems function like west coast rock lobster and abalone. This can have cascading effects in the food web, change the functioning of kelp forest ecosystems and threaten the livelihoods and way of life of fishers. Abalone and west coast rock lobster resources are severely overexploited with escalating poaching preventing recovery of these valuable resources. The illegal abalone trade is estimated to be almost double the volume of legally caught abalone or that produced by aquaculture operations. Resource recovery plans need to be implemented and fishing quotas need to be allocated in line with scientific recommendations that account for the realities of resource abundance. Abalone and rock lobster poaching should be addressed and new methods considered to co-manage resources. Seafood consumers can play a role through their choices. More information on sustainable seafood choices can be found at Overexploited resources can recover in well managed no-take zones of Marine Protected Areas. In areas closed to fishing, resource species can grow and breed and spill over into adjacent areas where people can fish. Restricted or no-take zones in Marine Protected Areas (MPAs) like Namaqua National Park, Table Mountain National Park, Robben Island and Betty’s Bay help protect kelp forest ecosystems. The Agulhas Bank Complex protects offshore pinnacles with different kelp species and a different kelp forest ecosystem type to those along the coastline.

Monitor Kelp Forests and mitigate climate change – Like many ecosystems, climate change affects the functioning of kelp forest ecosystems. Kelp forests are dependent on cold nutrient-rich water. Climate change is altering sea temperatures, changing frequencies of phytoplankton bloom occurrences and shifting upwelling events. These changes to the conditions that Kelp Forests need to survive and grow, can affect where they grow and who can live there. Globally, Some kelp forests are being reduced in size or even lost due to climate change. Individuals can make small impactful changes to reduce their carbon footprints and encourage lawmakers to adopt strategies that reduce and adapt to climate change. 

Reduce and manage pollution – Chemical pollutants and sewage can affect the creatures that call kelp forests home. Plastic pollution can severely affect the survival of birds, fish and mammals. Our individual choices and actions can affect the amount of plastic pollution on the coastline. We should choose to reduce our plastic waste and recycle what we can. Responsible practices by industry and government to avoid and manage pollution coastline should be encouraged to maintain the health of ecosystems. The location of pipelines must be considered in spatial planning and should avoid critical biodiversity areas.

How do we learn more?

Kelp Forests occur in the cold and cool waters of the West and South Coast. They are popular tourism and recreation sites with an increasing appreciation for their beauty, history and opportunities to connect with the ocean. To learn more about Kelp Forests and the people associated with Kelp Forest ecosystems in South Africa, explore the following websites:

Loyiso Dunga

Marine research scientist (Biology and Environmental monitoring) at Kelp Blue Namibia

Studied: Bachelor of Science (University of the Western Cape), Bachelor of Science, Honours (University of the Western Cape), Master of Science (University of Cape Town)

What is interesting about the ecosystem you are working in?

Kelp forests are incredible habitat formers, providing a place for shelter, protection and intricate foodwebs. They are like trees that live underwater, how cool is that? They also protect the coast from harsh waves providing sheltered areas for fishermen to work. Kelps are mesmerising and come in different shapes and sizes. They are beautiful places to work and there is so much to see in these complex ecosystems.

What are the challenges with working in your ecosystem?

The key challenge is accessing the ocean to study kelp forests in greater detail. The ocean can be scary and should be approached with caution. This makes studying kelp weather dependant and often needs equipment that can be costly. In South Africa alone, kelp forests ecosystem span about 1500km and it is a real challenge for scientists to explore and understand such a vast length of coastline. Monitoring kelp forests at a national scale is expensive and we need to use modern technology to track kelp forests in a more cost-effective approach.

What are you working on and why is it important?

I worked on mapping South African kelp ecosystems to know what types we have, where they are and how to protect them. Currently, I am working on growing giant kelp forests offshore to expand kelp forest habitat for harvesting and help remove carbon dioxide from the atmosphere thereby contributing to global climate change mitigation.

Mzansea: revealing south Africa's marine ecosystems Logo

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