This weekend I happened to be passing one of my favorite tide pooling areas at high tide on the way elsewhere. The storm offshore was already affecting the ocean with aggressive, high waves vigorously crashing into the shore. Interestinly enough, it is not nearly the highest tide expected this month, although I suspect it might have been the most impactful. I have regularly stood exactly where this wave came through, looking at crabs, seaweeds, kelps, and barnacles galore. Today, that wave would have been well over my head.
Tide pool creatures often look delicate and fragile, but nothing could be further from the truth. It has been said that the intertidal area might well be one of the harshest places on earth to "make a living".
The top photo highlights perhaps one of the most obvious stressors - the impact and ripping effect of forceful waves during regular storms that approach the coast. Holdfasts of kelp may be ripped free, leaving the plant helplessly drifting in the surf. Small fish and animals may be driven into the many boulders that inhabit the rocky coast. Sand and silt is stirred, clogging the filtration structures which many tidepool animals rely on to sift phytoplankton from the water and to breathe. Barnacles which have been growing for months may be crushed or broken loose. The amount of physical damage from such a storm can be tremendous. And the risks extend to creatures of the surface as well - I watched a female merganser being pummeled repeatedly as the surf ebbed and flowed. Studies in harlequin ducks have revealed that many adult birds have suffered fractures from their life in the rough surf.
Massive waves are only the start of the dangers of life in tide pools. One that might not immediately be obvious is the marked change of temperatures that these animals experience as the cold ocean water recedes, and the warm (think summer!) sun bakes the thin layers of water that remain -- only to be deluged with chilly ocean water again a few hours later. In the winter, the reverse may be true - these animals are now exposed to the sometimes below zero air temperatures, particularly if they are above the tide line and left stranded. Which brings to fore an additional problem - dessication. As the water recedes, the tidepool creatures must find a way to adapt to life without the protective blanket of water which often brings them food, oxygen, warmth (or cold), and shelter.
If these stressors weren't enough - then comes rainstorms and runoff from shore. These creatures, which are adapted primarily to the salty environment of the ocean, are now exposed to fresh water not only falling from the sky, but also rushing in from the surrounding freshwater rivers and streams. In order to survive in the tide pool, these animals must be able to also adapt to huge fluctuations in salinity. Of course, on top of all of this, everything and anything would like to eat them -- so predators add an additional layer of stress to the scenario.
In general, organisms have an easier time living in low-stress, stable habitats than in highly stressful, variable habitats. Therefore, there is higher diversity (more species) as one travels lower in the tide pool zones and the fluctuations in the habitat are reduced. But in the upper parts of the tide pool, such as in the splash zone, the habitat is very variable and stressful -- so there are fewer species that are able to survive here and diversity is lower. This is why it is ideal to tide pool during a lunar low tide, when the water allows easy access to the deeper areas of the pools.
These small, delicate appearing animals are fascinating to watch and spend time with. And even more amazing when you consider the massive environmental variations which they survive - and even thrive in. They may look fragile, but they can withstand much more drastic changes in their "home" environment than any human can!
If you are interested in learning more about the critters in the tide pool - please come to a presentation I'll be giving soon:
And this week is a super fun Instagram quiz -- with a bird that I stumbled on quite by accident while exploring in Eastport during a snowstorm. My initial impression changed after I got a good look at the bird. Can you identify it just by face? Check your answer on my Instagram page (or email me!).