Intertidal ecology
[1][2] Organisms living in this zone have a highly variable and often hostile environment, and have evolved various adaptations to cope with and even exploit these conditions.
[5][6] Soft-sediment habitats include sandy beaches, and intertidal wetlands (e.g., mudflats and salt marshes).
Rocky shores tend to have higher wave action, requiring adaptations allowing the inhabitants to cling tightly to the rocks.
Soft-bottom habitats are generally protected from large waves but tend to have more variable salinity levels.
[7][8] Because intertidal organisms endure regular periods of immersion and emersion, they essentially live both underwater and on land and must be adapted to a large range of climatic conditions.
These adaptations may be behavioral (i.e. movements or actions), morphological (i.e. characteristics of external body structure), or physiological (i.e. internal functions of cells and organs).
[10] Besides simply living at lower tide heights, non-motile organisms may be more dependent on coping mechanisms.
Types of substrate attachments include mussels' tethering byssal threads and glues, sea stars' thousands of suctioning tube feet, and isopods' hook-like appendages that help them hold on to intertidal kelps.
Higher profile organisms, such as kelps, must also avoid breaking in high flow locations, and they do so with their strength and flexibility.
Additional forms of mechanical stresses include ice and sand scour, as well as dislodgment by water-borne rocks, logs, etc.
For example, the tiny crustacean copepod Tigriopus thrives in very salty, high intertidal tidepools, and many filter feeders find more to eat in wavier and higher flow locations.
During tidal immersion, the food supply to intertidal organisms is subsidized by materials carried in seawater, including photosynthesizing phytoplankton and consumer zooplankton.
[13] The adjacent ocean is also a primary source of nutrients for autotrophs, photosynthesizing producers ranging in size from microscopic algae (e.g. benthic diatoms) to huge kelps and other seaweeds.
Intertidal habitats have been a model system for many classic ecological studies, including those introduced below, because the resident communities are particularly amenable to experimentation.
Classic studies by Robert Paine[13][15] established that when sea star predators are removed, mussel beds extend to lower tide heights, smothering resident seaweeds.
Similarly, Chthamalus, which occurs in a refuge from competition (similar to the temperature refuges discussed above), has a lower tide height limit set by competition with Balanus and a higher tide height limit is set by climate.
For example, salt marsh plant species of Juncus and Iva are unable to tolerate the high soil salinities when evaporation rates are high, thus they depend on neighboring plants to shade the sediment, slow evaporation, and help maintain tolerable salinity levels.
Additional important species interactions include mutualism, which is seen in symbioses between sea anemones and their internal symbiotic algae, and parasitism, which is prevalent but is only beginning to be appreciated for its effects on community structure.
Ultimately, it has been predicted that the distributions and numbers of species will shift depending on their abilities to adapt (quickly!)
[20] Due to the global scale of this issue, scientists are mainly working to understand and predict possible changes to intertidal habitats.
