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Rough Life on a Rocky Shore 

Have you ever spent an afternoon exploring the rocky intertidal zone of the Humboldt coast at low tide? If so, you may have wondered to yourself how a thriving ecosystem can exist in such a seemingly unfavorable habitat. Inhabitants of the rocky intertidal include marine invertebrates, which spend their entire lifetime exposed to an extreme range of environmental conditions. However, despite the many odds stacked against them, these spineless creatures have found ways to adapt both physiologically and behaviorally in order to survive.

As the daily tides rise and fall, inhabitants of intertidal communities are periodically emmersed -- stranded out of the water -- for many hours. This is when they face their biggest challenge. While exposed, extremely hot and dry conditions put these soft-bodied animals at risk of being dried up -- a process known as dessication. In order to prevent dessication from occurring, intertidal organisms have developed a number of effective strategies. One of these strategies is easily observed: The organisms gather together into dense groups. By doing so, they reduce their body temperatures and minimize evaporation into the surrounding dry air.

Another approach to avoiding dessication is to be selective of the microhabitat in which one resides. By living in a crevice or amongst a bed of algae, intertidal species can find shady relief during times of emmersion. Certain species have also acquired physiological defenses. Some are able to enter into a state of dormancy -- called aestivation -- in which slowed metabolic rates allow them to shut themselves off to the surrounding environment.

A range in tolerance to dessication plays a large role in determining where certain species can exist within the intertidal. In fact, the livable range for most species is so predictable that scientists have developed a number of zonation schemes. Next time you go tidepooling along the coast, try to see if you can observe a particular pattern of zonation. You should find that animals with protective shells, such as limpets and barnacles, will be found in much higher zones than soft-bodied anemones and nudibranchs.

Now, considering the perils of heat and dryness in the intertidal, try to imagine how these animals might be affected by the threat of global climate change. Temperatures could potentially begin to rise at rates which exceed an adaptive response by these organisms. If this future becomes reality, life could become very worrisome for the animals that call our rocky shores home.


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Emily Wilson

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