WINDOWS TO THE SEA
Rocky Shores, Rotsagtige kuste, Unxweme olunamatye
Fascinating rocks and pools changing from land to sea, providing food and places to meet many sea creatures
© Peter Chadwick
What are Rocky Shores?
Rocky shores are the rocky places between land and sea and are one of the easiest ecosystem types to visit. People have a long history of collecting food from rocky shores. These magical intertidal habitats are common along the entire South African coastline – making them familiar to many South Africans. Rocky shores are windows into the sea and by looking closely into tidal pools we can spot the kinds of creatures that live in deeper parts of our ocean.
Rocky platforms, boulders, pebbles and tide pools create homes for many different animals and seaweeds -but surviving on the rocky shore is not easy. Most animals have adaptations that allow them to thrive in this harsh environment and can withstand waves that knock them off the rocks; drying out and high temperatures during low tide; and predation. Mussels, barnacles and limpets attach themselves firmly to rocks and have protective shells to keep them moist and safe from predators. Many animals can move to avoid drying out, hiding beneath rocks, within rock pools, among seaweed gardens or between dense mussel beds.
Rocky shores occur all along the South African coastline, from the cold West Coast to the warm East Coast. Some famous rocky shores are Shaka’s Rock, Treasure Beach and Mission rocks in KwaZulu-Natal; Cove Rock and Cape Recife in the Eastern Cape; Dalebrook and Cape Agulhas in the Western Cape; and the beautiful rocky shorelines of the Namaqua National Park Marine Protected Area in the Northern Cape
Who lives on Rocky Shores?
The most familiar animals on the rocky shore are the mussels, limpets and snails that humans have harvested for thousands of years. As rocky shores occur from the West Coast to the East Coast, you find different seaweeds and animals as you travel along the coastline with species like the brown mussel more common in warm water, while the ridged mussel is common on the cold West Coast. Many seaweeds and animals that live on rocky shores are endemic to South Africa and occur nowhere else on earth.
Rockpools are one of the most interesting habitats on rocky shores. The world within the small area of a tidal pool is busy, complicated, connected and visible just by looking through the ‘window to the sea’.
Seaweeds produce their own food from sunshine and form the base of the food web on rocky shores. These algae- including microscopic algae called phytoplankton- use sunlight to make their own food and are known as primary producers. They provide food for grazers and filter feeders. Grazers, like limpets, are key parts of the ecosystem. They keep seaweed gardens trimmed but are also food for shorebirds, humans and other predators.
Filter feeders like mussels, barnacles and some worms grab tiny food particles (plankton) floating in the water. Mussels open their shells when submerged by tides, and provide important places for smaller animals like barnacles and worms to live. Barnacles attach themselves firmly to a surface (rocks or mussel shells) and use their modified feathery legs to draw plankton from water.
Feeding on the abundant grazers on rocky shores are predators and scavengers. Small invertebrate predators like sea anemones, sea stars, crabs and the common octopus. Other predators within tidal pools include blennies and small klipvis. Seabirds and mammals like the Cape Clawless Otter are frequent visitors to some rocky shores.
Why are Rocky Shores important?
Rocky intertidal shores are among the most productive, colourful and interesting ecosystems in South Africa. They are special places where we can collect food, explore, play and learn.
Rocky shores have a deep cultural significance for humans, and play a leading role in the story of human origins. For thousands of years, humans have harvested the seaweeds and animals that live on Rocky Shores for food. Limpets, turbos (alikreukel) and mussels provided early humans with essential fats and nutrients critical to brain development. This is thought to be important in the development of modern humans. Today, many of these species are still harvested and eaten and people continue to benefit from these rich resources. Traditional harvesting of food from rocky shores is also an important cultural practice that reflects deep connections between people and the ocean. Scientists are in the process of researching the value of red and brown seaweeds in medicines and some seaweeds are already used to produce commercially valuable products like agar.
Rocky shores provide outdoor classrooms where we can learn and explore the ocean while only getting our feet wet.
Rocky shores are also important tourism assets and attract people to the coast, supporting different coastal businesses. People use Rocky Shores as places for recreation, and shore anglers spend hours waiting on the edge of the rocks for a bite on their fishing hooks. Rocky shores also provide an essential food source for coastal animals. The Cape Clawless Otter, shorebirds and even coastal baboon populations depend on food from rocky shores.
How do we care for Rocky Shores?
As rocky shores are at the boundary of land and sea, they face pressures from both terrestrial and ocean activities. Caring for Rocky Shores requires us to:
Manage fisheries resources and avoid overharvesting – Many people depend on rocky shores as a place to harvest food, however the level and method of harvesting must be sustainable to avoid overharvesting. Remaining within harvest limits helps secure resources for the future. When harvesting food like mussels and oysters, from rocky shores, use sticks and screwdrivers, which have a lower impact than wide blade instruments like spades. If large patches of mussels are completely cleared of mussels, seaweeds usually occupy the area making it difficult for young mussels to re-establish. Baby mussels need adult mussels to work out where to settle and usually grow in between adult mussels.
Marine Protected Areas (MPAs) help to safeguard some of our Rocky Shores and no-take zones help manage important resources. MPAs protect Rocky Shores from activities like mining and coastal development and unharvested areas (no-take zones) help support harvesting outside of MPAs. MPAs that protect Rocky Shores include: Namaqua National Park, Table Mountain National Park, Tsitsikamma National Park, Addo Elephant National Park and iSimangaliso MPA.
Prevent and manage alien species – These species travel from their native ecosystem, through human transport like yachts and ships or are even introduced from marine farms. Alien species can completely change Rocky Shores and threaten the functioning of local ecosystems. It is critical that further invasive species are prevented from establishing on South Africa’s Rocky Shores. Protocols are needed to prevent invasion, monitor, detect and readily act to manage potential invasive species. South African scientists are researching methods of improving the monitoring of invasive species and managing their spread.
Reduce and manage pollution- Chemical pollutants, sewage and even nutrient enrichment from fish farms or fish processing factories can make it impossible for living things to survive in rock pools. Pollution that is high in nutrients can cause algal overgrowth in rock pools, resulting in the oxygen content in pools dropping to such low levels that no creatures can survive. Plastic pollution and other waste on Rocky Shores can severely affect the survival of invertebrates, 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 curb pollutants on the coastline must be encouraged to maintain the health of ecosystems.
How do we learn more about Rocky Shores?
Scientists, who study Rocky Shores, work in an exciting environment that sustains large amounts of life and provides us with unique opportunities to observe and experiment. Many scientists, who study Rocky Shores, work in an exciting environment that sustains much life and provides us with unique opportunities to observe and experiment. Some researchers, study relationships between animals on Rocky Shores such as interactions between native and invasive species or interactions between predators and prey. Other scientists study the impacts of pollution, the benefits of Marine Protected Areas and ways of maintaining our South African biodiversity.
Marine Bio-technician at South African National Parks
Studied: Bachelor of Science (Walter Sisulu University), Bachelor of Science, Honours (University of Transkei)
What is interesting about the ecosystem you are working in?
I work mainly on protected Rocky Shores within the Table Mountain National Park in the Western Cape. What interests me about this research is that the Marine Protected Area (MPA) lies at a transition zone between the Agulhas and Southern Benguela ecoregion with one side of the MPA having completely different species to the other. Secondly, the presence of dense bands of limpets occur inside the MPA that you won’t find outside the MPA.
What are the challenges with working in your ecosystem?
Sampling the Rocky Shores means you need to be punctual and have a plan of what to do when you get to the rocks. Rocky Shores are only available to work on for a short time during the day (4hrs) and missing this opportunity means having to come back the next day or weeks later. There are also times when the sea is rough, and it becomes impossible to work so you have to wait for the next spring tide.
What are you working on and why is it important?
My research is focused on understanding the role of Table Mountain National Park MPA in protecting biodiversity. This is important because MPAs are designed as management tools to protect biodiversity from human induced impacts such as harvesting. Therefore, it is important to know whether they are actually succeeding in the role that they were established to achieve.