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General Information. Bottom consists of sediment instead of rockUnstable and constantly shift in response to tides, waves and currentsNo place for organisms to attachMost animals burrow into the bottomThese organisms are referred to as infaunalVery few marine plants. Physical limits for life. S
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1. Soft Bottom Intertidal
2. General Information Bottom consists of sediment instead of rock
Unstable and constantly shift in response to tides, waves and currents
No place for organisms to attach
Most animals burrow into the bottom
These organisms are referred to as infaunal
Very few marine plants
3. Physical limits for life Sediment grain size
Whether it is clay, silt or sand
Sediment sorting
How much of each type of sediment is present
Desiccation
Sandy sediment dries out faster than clay or silt
Not as big an issue as in a rock shore
4. Oxygen Availability Since no light penetrates the sediment no photosynthesis takes place – no oxygen is produced
Sandy sediments are more porous than muddy sediments therefore, water associated with sandy sediments is mixed with water from the water column more efficiently and has a higher oxygen content
Muddy or clay sediment is densely packed and does not exchange water so it becomes anoxic quickly
Animals that live in this biome pump water into their burrows with siphons, some are very sluggish reducing the need for oxygen, and some have symbiotic bacteria
5. Anoxic Waters Refers to those waters that have no oxygen
Some have a rotten egg smell due to the presence of hydrogen sulfide produced by anaerobic bacteria
Areas that have a lot of this bacteria have black sediment layer because the bacteria reduce iron
6. Mobility Some mollusks burrow using their radula
Heart urchins use their spines and tube feet to burrow
Some animals eat their way through the sediment – sea cucumbers and worms
Some animals are so small they can squeeze between the grains in the sediment – called meiofauna
7. Feeding Detritus is the main food source
Many organism eat the sediment – extracting whatever nutrients they can
Some organisms collect particles as they settle out of the water column
These are considered suspension feeders
Some carnivores burrow through the sediment looking for organisms that have burrowed in and then consume them
Some fish come into the area at high tide an nibble on the exposed siphons
8. Zonation Not as obvious as in the rocky shore area
Sandy beaches have the most zonation of any soft bottom shore
Water drains quickly from the high tide areas creating physical limits to life
Upper beaches tend to be drier than lower beaches
9. Upper Beach Dry
Inhabited by beach hoppers, isopods, ghost crabs and fiddler crabs
10. Lower Beaches Wet – covered with water for a lot of the time
Inhabited by polychaetes, clams and other organisms