Note: This program first aired December 1, 2012.
Looking through an old resume recently, I noticed that I listed “tidepool fanatic” on my list of other skills and interests. Seriously, and it got me the job too. And I am not the only one; there are millions of us*, you can find us pawing through seaweed, looking under rocks, and staring into tide pools every time we go to the edge of the sea. The organisms we find in the intertidal zone are our windows to the mysteries of life under the ocean surface. Twice daily the veil is pulled back and the tribe of the curious gathers to explore the unknown.
The intertidal zone is the area at the edge of the ocean that is regularly covered and uncovered as the tide rises and falls each day. Places like Maine, with high tidal ranges have a large and diverse intertidal zone. Places like Florida, with very small tidal ranges have minimal intertidal diversity. The intertidal zone is populated with marine organisms, meaning organisms adapted to live in the salty aquatic environment we call the ocean. These are some of the toughest organisms in the world, and this is why: imagine yourself as a land based, air breathing being, having to survive, day after day, totally submerged in sea water half of the time. This would certainly challenge your physiology, to put in nicely. This is the kind of challenge (albeit in the opposite direction) that organisms in the intertidal zone face twice daily, every day. As organisms dependent on the ocean’s water, they are stranded out of it for some, if not most of their lives.
Consider the benefits of the ocean, if you are a marine organism that is. Being submerged in water means that you can breathe; water brings with it food for many organisms, water provides a medium for motility (and breeding and hunting), water provides environmental stability in terms of temperature, salinity and pH, in short, the intertidal zone comes alive at high tide. Consider the difficulties of living in the terrestrial environment, if you are a marine organism. You can’t breathe air (with a few exceptions), the temperature and salinity can fluctuate dramatically with season and weather events, you can’t eat, and you could easily dry out. If you are algae, you just have to lay there as you fell. Its rather undignified when you think about it. Clearly, these organisms would be much better off if the tide just came in and stayed in.
Or so we think. The reality is that the organisms we see in the intertidal zone live in this marginal environment because they get outcompeted (which is just the scientific word for bullied) in the sub tidal environment. The intertidal organisms do better in that incredibly stressful intertidal zone, because they evolved physiologic and structural adaptations that protect them from drying out, suffocating, cooking and freezing. Subtidal organisms just can’t do that. Take them out of water and they die.
I have huge respect for the resilience of the intertidal organisms. They eke out a living in a consistently inconsistent habitat, organisms of the ocean that can exist on land, at least temporarily. This sounds pretty significant, but how different is it from our own situation? We humans are predominantly visual animals, yet, we evolved in and exist in an environment that grows dark for half of the time we are in it, effectively negating our primary sense. So perhaps the achievement of the intertidal organisms isn’t as amazing I led you to believe. I don’t care, you’ll still be able to find me staring into the nearest tide pool, imagining the scene when the tide comes in and all of the organisms live the fullest expressions of their lives. Perhaps that is why so many of us love the edge of the sea. Its rhythms of activity and rest, and abundance and famine so readily mirror our own.
*Full disclosure: this is a complete guess.
References:
Oh there are so many books on the intertidal environment! Though it is old, I still love the Sierra Club Naturalist’s Guide to the North Atlantic Coast (Cape Cod to Newfoundland) by Michael and Deborah Berrill.
