Thursday, August 6, 2015

Life in the Intertidal Zone

The intertidal zone is the area between the high and low tide lines.  It is an area rich in nutrients and is the home to a variety of inhabitants, but it is a harsh habitat where the inhabitants have to survive in both the sea and on the land.  The Intertidal has four distinct zones. The spray zone is submerged only during very high tides or during storms, but will be 'sprayed' by sea water by splashing waves and wind-blown spray. The high intertidal zone is submerged during the peak of the high tide and is out of the water for long periods between the high tides. The middle intertidal zone is typically exposed during the hours surrounding the low tide and low intertidal zone is exposed only during the lowest tides.

Most human visits to Haystack Rock are during low tide when much of the intertidal zone is exposed and the inhabitants are exposed to the air. While the human visitors leave as the water submerges the landscape with the incoming tide, the inhabitants remain and have must survive under the water.


Haystack Rock at Low Tide
Intertidal Zone exposed to the air
Photo courtesy of Carolyn Propst


Haystack Rock at High Tide
Intertidal zone covered by water
Photo Courtesy of Carolyn Propst

The inhabitants of the intertidal zone have to adapt to huge daily changes. At high tides the inhabitants are covered with salt water but are exposed to the air at low tide, so they must be able to survive in both. When submerged, the inhabitants are subjected to the turbulence of the water that can dislodge or sweep them away so they will burrow into the sand, attach to rocks, or live under rocks. While submerged, the temperature remains relatively constant but, when exposed, the air temperature can range from below freezing to extreme heat. Tidepools that form during low tides can have a salinity near that of the sea or much lower when rainwater or runoff dilutes it and the inhabitants have to adapt. The inhabitants also have a variety of predators - when submerged by the tide they are preyed upon by sea animals and when exposed birds and marine mammals will prey on them.

There are many inhabitants of the intertidal zone that thrive at Haystack Rock and can be spotted near low tide.


Sea Stars and Anemones
Photo Courtesy of Carolyn Propst


Chitons
Photo Courtesy of Carolyn Propst


Mussels and Anemones
Photo Courtesy of Carolyn Propst


Nudibranch
Photo Courtesy of Carolyn Propst

The Haystack Rock Awareness Program is committed to educating visitors about the inhabitants of Haystack Rock and conveying the importance of protecting them while they are exposed at low tide. HRAP Interpreters are on the beach every day at low tide and are happy to answer any questions you have about the inhabitants of the Intertidal zone!

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