benthic exam 2 - The Ecologies of Unvegetated Intertidal...

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The Ecologies of Unvegetated Intertidal Sandy Beaches and Mudflats The intertidal regions of the coasts represent a continuum of habitats with different physical, chemical, geological, and biological conditions. Sandy beaches and mudflats are no exception. The different energy regimes are the main cause for the differences in the physical and geological environments in these areas. Beaches are generally exposed to the open ocean and experience energetic waves, tides, and currents that either restrict the deposition of fine material or carry away fine particles leaving behind sediments in the “sand” size category. Mudflats however are generally located in protected bays, estuaries, and lagoons where the lower energy regime allows for the deposition of fine grain mud and silt. Water velocities in these areas are generally too low to carry and deliver any sand. The intertidal zone itself also exposes resident organisms to a suite of stresses resulting from the rhythmic periods of exposure and immersion. These organisms experience wide ranges of temperature, salinity, dissolved oxygen, and food supply and therefore must be specially adapted to deal with this harsh environment (Levinton 2001). The physical, chemical, and geological aspects of any environment play a large role in determining the ecology of the region. The ecology of beaches is considered to be largely controlled by the physical environment. Waves, tides, swash width, and particle size are cited as the main components. These factors interplay to create a continuum of beach types based on their morphodymanics from reflexive (larger waves, particles, and slope) at one end to dissipative (smaller waves, particles, and slope) at the other (Brown and McLachlan 1990). Numerous studies have found that species abundance and diversity increases from reflexive to dissipative beaches (Brown and McLachlan 1990, Defeo and McLachlan 2005, Lastra et al 2006). The energy in a reflexive beach is too high to allow organic matter to settle and water velocities are too high to allow effective filter feeding. The community of organisms found on sandy beaches is almost entirely made up of filter feeders or predatory organisms. The energy of
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This note was uploaded on 04/13/2008 for the course MSCI 479 taught by Professor Koepfler during the Spring '08 term at Coastal Carolina University.

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benthic exam 2 - The Ecologies of Unvegetated Intertidal...

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