Love Your Wetlands – Instalment 3: Setting the Record Straight Many find it difficult to point out exactly where the salt marshes begin and where the estuary stops in the Knysna estuary. Below are 3 simple definitions which should help. 1. Estuary or Lagoon? There is much overlap in the usage of the terms coastal lagoon and estuary, and in some cases, it is very difficult to distinguish one from another. Estuary: An estuary is the point at which a river and the sea meet. Estuaries are, therefore, dynamic ecosystems where seawater is brought in by the tides but is diluted by freshwater flowing in from rivers and streams. Estuaries are usually quite deep. Lagoon: A coastal lagoon is a shallow, coastal body of water, separated from the ocean by a barrier. This barrier can be formed by a coral reef, barrier islands, a sand bar or less frequently, rocks. The depth of a lagoon seldom exceeds a few metres. A quick an easy look at the differences between the two: Source: https://cmsdata.iucn.org/downloads/lagoons_and_estuaries_book.pdf 2. Wetlands A wetland is any area that holds water either temporarily or permanently. Some wetlands hold water year-round while others may only hold water for one or two months each spring. Since wetlands lie at the interface of terrestrial and aquatic habitats, they possess a unique mixture of species, conditions, and interactions. As a result, wetlands are among our planets most diverse and varied habitats. Types of Wetlands include springs, swamps, bogs, pans, lakes, estuaries, floodplains, billabongs, lakes, lagoons and mangroves. 3. Salt Marshes Salt marshes are coastal wetlands found throughout the world on the edges of estuaries where freshwater mixes with seawater. Although they might not look particularly attractive to you and I, salt marshes are the foundation upon which much of the estuarine food chain is built. The plants which grow in salt marshes have to be specially adapted to withstand one of the worlds harshest environments. The salt marshes of the Knysna Lagoon are flooded by tides twice a day. When the water rises, the temperature surrounding the plants drops sharply and the oxygen supply and light intensity are reduced dramatically. Notwithstanding these adverse conditions, the plants cope extremely well, and it’s been estimated that the average salt marsh can produce more food per hectare than any of mans most advanced agricultural systems. Melaney Barrath is a People and Conservation Officer for the Knysna section of the Garden Route National Park.
Posted on: Thu, 30 Jan 2014 06:27:48 +0000
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