Aquatic ecology and Biodiversity

Unit 11- Intertidal zone

11.3.1. Ecosystem properties
There is no significant primary production, except by blue-green algae and diatoms that occur on the surface of sandy mud in sheltered conditions. Energy input into the system is from the phytoplankton in the water and from particulate organic matter (detritus) derived from the land and adjacent intertidal habitats. Herbivorous and detritus feeding and carnivorous animals are included in the sand infauna. Carnivores include fishes crustaceans and birds.
Environmental characteristics
• Sand grains are quartz particles mixed with shell fragments
• Sand particle size varies from < 0.1 to 2 mm.
• Sandy beaches typically have a gradual slope means, sediments drains and dries slowly.
• Oxygen decreases with depth of soil
• Anaerobic conditions are due to sulphide layers.
• Substrate is unstable due to tidal water
• Continual shifting of the surface layer
• Sand contain relatively low organic matter
• Organisms burrow into sand dig low tide
• No large attached plants
• The dominant printing producers – diatoms, dinoflgellates and blue green algae
• Primary productivity is very low <15g Cm²/yr