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There are eight species of Ulva found in the world; Ulva lactuca is the species present on Race Rocks. However, Ulva lactuca is not specific to Race Rocks. It is found in upper intertidal zones along the Pacific coast from Alaska to Chile. The ideal conditions for Ulva growth include warm area's, and rich nutrients. On the coast of Chile 200 metric tonnes of Ulva must be harvested daily for an 8 month period because it becomes very smelly when large populations begin to rot. Over population of Ulva is responsible for the phenomenon know as "green tides". Some countries culture Ulva and use it in condiments for soups and salads. Others used it was a source of manure. At Race Rocks this species of algae is not abundant due to the exposure of waves at low tide.
Ulva begin life a filamentous plants but develope into blade-like plants. A mature Ulva can be described as a fan shaped flat blade. The blade is two cells thick and varies greatly in length (often less than 30 cm long; however specimens on Race Rocks are usually within 20 cm. The blade contains two forms of chlorophyll thus giving it a color ranging from pale green to emerald green. Beneath their blade-like structure is a holdfast which is used to attach to a rock substrate . Although most Ulva is found attached to rocks it can also exist as a free floating organism, after being torn up by waves.
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Sources - Pacific Seaweeds by Louis Druehl p15, 19, 26, 50, 53
Common Seaweeds of the Pacific Coast by Robert Waaland p 12, 23,28,30,32,36,37,40,96,37
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