West Coast National Park Tsaarsbank
West Coast National Park Postberg
West Coast National Park Plankiesbaai

West Coast National Park - Langebaan Lagoon Ecosystem

The West Coast National Park is home to the Langebaan Lagoon, which is a wetland if international importance. 

The Langebaan Lagoon was shaped by the rise and fall of sea levels during pre-historic times. This is quite unlike typical lagoons which form where fresh water rivers enter the sea. The result is a purely salt water lagoon. 

The Langebaan ecosystem is a dynamic system that relies on the interaction between the various atmospheric, aquatic and terrestrial factors and elements. Their interaction is of an interdependent nature and creates a self-sustaining ecosystem.

The basis of this ecosystem like all others are the abiotic substances like water, oxygen, nitrogen, carbon dioxide, salts etc. For the Langebaan Lagoon it all originates from the depths of the ocean with the ocean currents, wind and sun all working together. The cold benguela current that flows up the west coast brings nutrient rich water from the Antarctic. A combination of the ocean current and prevailing southeasterly winds result in a phenomenon known as upwelling. This upwelling forces nutrients consisting of decomposed matter from the seabed to be brought up to the surface along the shoreline. This decomposed matter is being continually regenerated by the decomposition of dead sea creatures. Further small plant matter is added to the water by the destructive forces of the waves on the vast kelp beds that line the  west coast. These nutrients provide food for the producer organisms like floating plants and phytoplankton. The suspended plant life utilise the available sunlight to grow and multiply thereby further increasing the availability of suspended nutrients.

It is this plankton that provides food directly for the primary macro consumer organisms. These are the shoreline filter feeders like muscles as well as many of the fish like pilchards and mammals like whales. The smaller fish then also serve as a source of food for bigger fish and sea birds that are referred to as secondary and tertiary consumers.

The daily change in the tides provides the mechanism to bring this nutrient rich water into the Lagoon. However not much of it actually reaches down the 15km length of the lagoon. This is largely due to the vast banks of clams under water at the entrance to the lagoon that are supported by this phytoplankton and filter it out. Harders also feed on a lot of the floating nutrients. The rest is used up by the sea grasses, salt marshes and reed beds on the edge of the lagoon. The salt marshes in the southern end of the lagoon utilise some of these nutrients and in turn release more phosphate rich nutrients into the water. The plants living in the shallows of the lagoon also provide a significant amount of nutrients to the lagoon itself. These nutrients come in the form of decayed plant matter from the seasonal dead flowers that are recycled by bacteria. The bacteria assisting with decomposition of plant and animal matter are referred to as saprotrophic organisms and form a vital link between living and non-living elements in an ecosystem.

In the Lagoon the filter feeders like mud prawns and blood worms rely on these nutrients from the decomposition cycle. These organisms then in turn provide a food source for fish and birds. The thousands of resident and migrant birds feed off the nutrients generated from the salt marshes as well as the sea creatures that live off these nutrients. The guano from these birds is returned to the lagoon and in turn provides vital nutrients back to the salt marshes.

This ecosystem is sustained by the nutrient cycle which allows nutrients to be recycled from the start of the process as abiotic substances, through to end consumers and then decomposed back to abiotic substances. The key energy source in this process is the sun, which provides the necessary energy to sustain the process. Since the ecosystem is like a chain, if any of the links are removed then the entire system can stop functioning. So no mater how small or insignificant, every little piece of the ecosystem is there for a reason and critical to its sustained existence.   

West Coast National Park Postberg
West Coast National Park Skrywershoek
West Coast National Park Seeberg

 

 

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