THE MOST EXCELLENT MARE TEACHERS’ GUIDE TO THE ROCKY SEASHORE by Dr. Robin Milton Love Introduction Did you ever notice that there are inside a crevice. There’s dripping and some things that everyone loves? streaming water, of course, and birds For instance, everyone on Earth loves calling and flying. But sometimes, if you oatmeal chocolate chip cookies. The truth are real quiet and put your ears close to is that for even the most humble among the rocks, you can also hear crabs us, if you give us an oatmeal chocolate walking, algae swishing in the pools and chip cookie, our fish flopping. lives are vastly SERENDIPITY And then there enriched. are an almost The rocky Trips to the intertidal are almost always excursions into infinite number intertidal zone the aesthetic. Very early one February morning I was of textures; exploring a pool at San Simeon (in central California). My is the oatmeal nose was running, my boots were filled with cold water and ranging from the chocolate chip the fog was in, muting all colors to dull browns, greens and sticky tentacles cookie of grays. The ledge I was examining was covered in fleshy of sea anemones, marine habitats algae, which totally obscured the underlying rock. I lifted the sharp spines of and you are algae up and on the newly-exposed surface was a Hopkins sea urchins, Rose nudibranch, a sea slug which is covered with jillions of indeed cute little protuberances and colored a remarkable cerise. knobbled skins fortunate to be The contrast between the muted, fog-shrouded rocks and of sea stars to among those this extravagant creature was wondrous. the almost able to explore These brief, subtle and quite unacademic moments, are unnaturally its wonders. marvelous gateways to discovery and curiosity. They are the silky skins of sea reasons you and your students will return to the tidepools Years from now again and again. As you practice slowing down and looking hares and other (when you are a closely, tiny and wonderful worlds will unfold more and sea slugs. And grouchy more frequently. mixed through octogenarian), all of this is that your one fond memory may be those remarkably thick, low-tide smell, redolent wondrous days spent among the rocks with life, death and decay. I would and crannies. mention the tastes in this habitat (a great And why is that? What is it about this many of the plants and animals are habitat that elicits such a response? edible), but we feel it’s better to look than Perhaps it is because the rocky intertidal to cook. is such a sensual, aesthetically pleasing What we are going to do in the experience; it engages your senses. First, upcoming pages is walk you through the as you look around, there is the sheer riot intertidal and talk about what it’s like of life that covers every surface and physically, what major organisms live pervades every crevice. And not only are there, how they cope with the physical there lots of living organisms; there are world and what impact humans have on often hundreds of different kinds. this remarkable environment. Frequently, the plants and animals will themselves be covered or invaded with Okay, What's It Like? other organisms and occasionally even First, you should realize that the rocky these will be homes for still more tenants. intertidal zone is a habitat with an Or perhaps it’s the sounds you hear if attitude. It is no picnic living there. When you are real quiet and sort of hunch down it comes to marine organisms, this is not a place for pencil-necked geeks. Of course, water (water tends to go into it). How can all organisms in all other environments our organism cope with these very have it tough; but most often they have to different environments? overcome living (biotic) challenges, like Then there is wave shock, the finding food, avoiding predators, or remarkably powerful force of crashing resisting diseases. Organisms in the rocky water. As I write this, I can look out the intertidal face these problems, of course, window of the Marine Lab and see waves but they also face the added dimension of roll over an intertidal ledge, then smash inhabiting an environment with extreme into a cliff, sending water 10 feet high. non-living (abiotic) conditions. How does our typical organism not get If you think about it, in one respect the swept away or crushed? Waves also help intertidal zone is totally different from all send water splashing up into the high other land and water communities. It is intertidal. But, unlike tides, they do this exposed to water part of the time and dry unpredictably. Organisms high up in the at other times. The equivalent on land intertidal can’t depend on large waves would be if, say, a redwood forest was in every day and must be able to withstand air part of the time and in a vacuum the prolonged periods of drying. rest. Because the water environment is so There are other potential problems different from the air, intertidal organisms from the environment. In polar or near- face an almost bewildering range of polar regions (i. e. Alaska or conditions in the course of a day, a season Newfoundland), ice forms on the shore or a year. lines, then scours the rocks as it moves. In What kind of conditions? Well, a much of the world, sand is carried onto typical member of the rocky intertidal (it the shore in summer (when the waves are could be a mussel, sea star, alga or crab) gentle), then carried offshore in winter faces a range of abiotic challenges. First, (with storm waves). In the process, some as the tide rises and falls, it is alternately rocky areas are sanded in during part of drenched and dried. When this happens the year, burying the intertidal organisms. the organism’s temperature can decrease Okay, this is obviously a pretty tough rapidly as cold water splashes its sun- place to live. Why don’t we talk a little warmed body or, alternatively, it can heat about the major factors that control what up as it is exposed to the air. This latter organisms live where in the intertidal. often happens in hot, tropical areas. Breathing is also going to be a problem, as The Big Factors what works in water (gills) may not be Tides very effective in air, and what works in Obviously, tides are a major (perhaps air (lungs) just can’t cut it in water. the major) controlling force in many Our friendly creature also has a intertidal habitats, because they help problem when it rains and it is pelted by dictate how long organisms are under fresh water. Remember that experiment water. Tides are rhythmic, predictable, you did in 10th grade biology? The one periodic changes in the height of a body where you put a nice crisp stalk of celery of water. The tides are caused by a in a glass of saltwater and the next day combination of the gravitational pulls of the stalk looked completely limp. Then, the sun and moon and the centrifugal you put the limp stalk in freshwater and, force caused by the rotation of the Earth/ voila, the stalk became stiff again. A body moon system. Throughout the year, tides responds differently when in salt water vary in their heights, and the highest (water tends to leave it), then in fresh highs and lowest lows occur together

2 during the new and full moons, when the several factors and the most important is moon and sun are directly aligned with the size of the area a wave travels through the Earth. These extreme tides are called without being hindered by islands or spring tides, which comes from the Old undersea ridges. The more wide open an English word springen, meaning to jump area, the larger the waves that can be or move quickly. Spring tides occur every generated. If you stand on the shore two weeks and alternate with less anywhere from Cape Flattery, northwest extreme neap tides. Washington to Pt. Conception in central Tidal patterns (how often highs and California, there is absolutely nothing lows occur within 24 hours) and ranges between you and the Aleutian Islands. (the difference between high tide and low That is a long way and it allows some tide water levels) differ in different parts fearsome waves to form. Of course, wind of the world. Some areas such as much of velocity is also important, which helps the east and west coasts of the United explain why waves tend to be higher States, usually have two high and two during storms. On much of the Gulf low tides per 24 hours. These are semi- Coast, waves tend to be small, and they diurnal tides. On the other hand, Gulf are a factor only during hurricanes and Coast states tend to have one high and other storms. Because waves have such a one low tide (diurnal tides) during the profound effect on sea life, any protection same period. Tidal ranges vary from their power alters the makeup of the dramatically, depending on the shape of animals and plants living in the habitat. the water basin the tides flow through. For instance, along the Pacific Coast, The narrow Bay of Fundy, in New wave-swept rocks are home to the Brunswick, Canada, has tides of about 50 powerfully-built sea star Pisaster (or ochre feet. Remember, this does not mean that star), which can hang on even when the water goes inshore 50 feet. It means slammed by direct hits from huge waves. that it rises in height that amount. So if In the same vicinity, but in protected the land is pretty flat, the sea might flow tidepools, lives the more delicate bat star, inshore for miles before reaching the Patiria, which can barely hold its own in necessary elevation. Tidal ranges for very mild surges. much of the west and east coasts of the The shape of the coastline has a large U. S. are around 6–8 feet. The Gulf Coast influence on wave action. The rocky tides are narrower, perhaps a foot or two. shores of open coasts, where waves come to shore unimpeded, tend to have Waves somewhat fewer plants and animals then Waves also play a major role in habitats in protected coasts, where the force deciding what organisms live where. Not of the waves is deflected somewhat. More only can waves knock organisms off their commonly, coastlines tend to be at least perches, they (along with tides) dictate partially protected, by offshore kelp beds, how high up into the intertidal water will reefs or by irregularities (such as splash. Far more territory gets wet during indentations) in the coastline. Somewhat a 6-foot tide with 10-foot storm waves, protected rocky shores are usually then with a 6-foot tide and one-foot placid chocked full of goodies, because waves. Though they help determine sea compared to the open wave-swept life along all shores, waves are habitats, they are an easier environment particularly important along much of the in which to live. Pacific Coast, where wave size varies a Rock position and location are also great deal. The size of waves depends on important factors. Because waves and

3 tides have such a large influence on the Drying out (and that includes changes in environment, not all places in the rocky temperature as well) and being dislodged intertidal are identical. Generally, the and killed by wave action. How do higher up the intertidal you are, the more organisms cope with these problems? extremes (in wetness, waves, wind etc.) you will face. Moreover, vast differences Drying out in these conditions may occur even on a Location in the intertidal is a main single rock. For instance, the top of the way animals find their drying out comfort rock is drier and more subject to wave zone. If they like it drier, they live higher action then a crevice. The southwest- up; if they like it wetter, further down. facing part of the rock (which faces the Even within a zone, there are differences sun most of the day) is drier than the in wetness and organisms take advantage north-facing side (which tends to be in of this. Crevices, cracks and holes are shadow). The crevice is probably drier shady and often contain pockets of water; and more wave-swept than the under here you will find those animals which parts of the rock. And the deep pool next prefer a bit more moisture. In fact, these to the rock is continually wet and slightly wetter areas allow organisms that probably quite protected from many would usually be found in the lower and waves. Commonly, different organisms wetter intertidal to live higher up. will be found in these different areas, Intertidal organisms, particularly those even if they are inches apart. high up the intertidal, often have shells which can be tightly closed or skins that Substrate are particularly thick. Both of these can If you think about it, the type of trap water and help provide protection substrate found in the intertidal also from evaporation. Some anemones cover effects what lives there. For instance themselves with bits of shells and rocks to granite is pretty tough stuff, it takes a lot provide shade. of waves and a lot of water to begin to crack, chip or flake it away. On the other Wave Action hand, sandstone or shale is (relatively First, as with protecting against drying speaking) pretty delicate; crevices, holes out, almost all the animals which live in and cracks develop quickly. These heavy surf have hard shells or tough openings provide habitat for many skins. Many of these organisms have also animals which cannot live on open rock. evolved clever ways to hang on in surge Therefore these softer substrates may conditions. Sea stars have tube feet, have a greater variety of organisms than mussels special tough threads with glue ones found on harder surfaces. On the on the ends and barnacles have a cement Gulf Coast, there are few natural rock so effective, even in a wet environment, outcroppings. Take heart, however, for dentists are thinking about using it to there are an abundance of rock jetties and keep fillings in place. Other organisms dock pilings to choose from. These find places where waves are disrupted or structures often provide homes for a blocked. Periwinkles, limpets and other myriad of organisms to choose from. snails tend to congregate in partially protected crevices. Sea urchins, hermit A Few Ways Organisms Survive in the crabs and sea slugs, to name a few, all Rocky Intertidal tend to live in protected pools. At the Let us assume that rocky intertidal extreme are boring clams with shells organisms face two major problems: resembling files. They bore into rocks and

4 live their lives sealed off from the intertidal only to have nothing to show environment, except for a small hole, them because the tide is too high. In through which water and food travel. reality, there is plenty of life to instruct and entertain What Lives ON ED RICKETTS your students, There? Thinking about zonation reminds me of Ed Ricketts. even in the Okay, we Hang around marine biologists and marine biologist highest zones. are done with wannabe’s long enough and you will inevitably hear the You just have to all the name Ed Ricketts, the author of Between Pacific Tides, that know what to most graceful and humane of field guides (and the source look for, and preliminaries. for much of the information in this text). Between the 1920’s We know what and 1940’s, Ricketts was the Pacific Grove-based specimen how to look. The factors collector, intertidal biologist and philosopher, with the libido secret is to get influence rocky of a weasel, who was the lightly-fictionalized “Doc” in John down on your intertidal Steinbeck’s Cannery Row and Sweet Thursday. There is no belly, move question that many of us want to be Ed Ricketts. slowly, look inhabitants, Ricketts was a most remarkable person, with an unusu- now let’s look ally fluid and unfettered mind; one that found inspiration closely, and be at what you are equally in tidepools, the Tao Te Ching by Lao Tzu and the patient. So let’s likely to see and poetry of Robinson Jeffers. It is a rare person indeed who start out with where you will could simultaneously influence zoology students at Stanford stuff you can University (many of whom absorbed and later researched find, and things see them. his ideas on intertidal habitats) and mythologist Joseph Probably the Campbell (a long-time friend and fellow seeker of inner you can see, if best way to do wisdom). In an age where most biologists on the Pacific you can only get this is to work Coast were content to identify and classify organisms, to the highest our way down Ricketts was asking how intertidal organisms related to one parts of the another and to their environment. He was particularly intertidal. the intertidal, interested in zonation, how and why organisms are limited from the to specific areas in the intertidal. Many of the questions he There is no highest splash asked were later taken up by a generation of modern-day question that as zone to those ecologists. you go down the rocks For more of the essential Ricketts, check out Log from the intertidal, from Sea of Cortez by Steinbeck and Ricketts. It’s a marvelous the high and dry uncovered only book, filled with humor, natural history, insights into the at the lowest of human condition and some remarkably obscure philosophy. to the low and low tides. I John Steinbeck, in his introduction to the Log from the Sea of wet, you will think we should Cortez, summed up his many years with Ricketts in this way: encounter pay particular “...no one who knew him will deny the force and influence different species. of Ed Ricketts. Everyone near him was influenced by him, Organisms attention to the deeply and permanently. Some he taught how to think, upper areas, others how to see or hear. Children on the beach he taught to arrange because, unless look for and find beautiful animals in worlds they had not themselves by your timing is suspected were there at all. He taught everyone without the amount of particularly seeming to.” time they can We would like to think that much of MARE is based on tolerate being out good and you the approaches pioneered by Ricketts. Ricketts was a fine catch a and respected scientist. He was also unpretentious and most of the water. In substantial low of all he had fun at what he did--just as we hope you and the highest tide, it is more your students will as you explore the Rocky Seashore. intertidal, the than likely you splash zone, will only be animals may be able to visit these higher levels. And let’s out of the water for days between high be honest here, there is little in life worse tides (and/or large waves) high enough than carting 33 small people to the to cover them. By the same token, in the

5 lowest of the intertidal, animals may be sea water and if you keep them uncovered for only a day or two a year. underwater, they will drown. On the Every species has a unique set of other hand, some have been kept high environmental requirements and if these and dry for up to 42 days without ill requirements are not met, the organism effect. Periwinkles, and for that matter eventually passes on to that great tidepool many other snails, use an operculum to in the sky. This is the basis for zonation, prevent drying out, to keep fresh the occurrence of organisms or groups of rainwater from getting in and to help organisms with the same requirements, in ward off predators. An operculum is like specific areas. In the case of the rocky a trap door; it’s a shell-like little intertidal, some zones are so well-defined contraption that the animal grows on the that they can be seen all around the back of its foot. When the snail pulls its world. As an example, in North America body into the shell, the operculum is and in Europe the little barnacle pulled in last and makes a neat little seal Chthamalus is always and only found in across the shell opening. This seal is highest part of the intertidal. It can live apparently extremely tight. Periwinkles lower down, but there it meets another have been fed to sea anemones, only to be barnacle, Balanus, which grows faster and spit out half a day later, with a nicely just pushes Chthamalus out of the way. polished shell but life intact. Like many Okay, if Balanus is so hot, why doesn’t it other intertidal snails, periwinkles are live further up; why can’t it push primarily vegetarians; they scrape the Chthamalus out of the highest intertidal? It rocks with a radula, a little bit of cartilage, turns out that Balanus can’t withstand the covered with lots of tiny teeth. Virtually dry conditions found in the uppermost any day you visit the intertidal you will intertidal. So, we can say that in the upper see periwinkles mating; they are the ones rocky intertidal there is a Chthamalus zone on top of one another. On some occasions and a Balanus zone. Naturally, the higher in the spring and summer, it is hard to the tidal fluctuation, the wider will be the find a periwinkle that is not mating. zones. But even on the Gulf Coast, which Tiny, dirty-white, brown or gray acorn has a relatively small tidal range, there are barnacles (Balanus or Chthamalus) are also discrete zones, though these bands may very abundant along the splash line. You be only a few inches each. will find these rather nondescript characters in large masses (often crowded The Uppermost Zone shell-to-shell) almost always on vertical, Don’t be fooled, despite what you or at least sloping, rocks. At first glance, might think at first glance, there are these animals appear to be dead; after all animals and plants here, but they may be they are not moving about, have no parts quite hard to see. Probably the most that are moving about and are very poor common critters are periwinkles, rather conversationalists. Most of these animals small snails, whose drab appearance are quite alive, merely waiting for the makes them tough to spot. While they perhaps one hour or so per week when may be out on the open rock, they most they get splashed. Despite their often prefer hunkering down in cool, appearance, barnacles are actually closely shaded crevices (of course, a crevice to related to crabs and shrimps. Basically, a them may be only one-inch deep). barnacle is a shrimp-like animal which Periwinkles are as close to a land animal has glued its head to a rock, grown a shell as you can get and still be aquatic. They about itself and catches food by thrusting like being doused only occasionally with

6 out its feet into the water. When it is out While smaller species cruise all over of water, it retracts its feet and securely the rocks, one kind, the owl limpet, closes off its shell opening with a set of actually does a bit of farming. Each night, hinged plates. The way to tell if the it patrols a territory and wards off animal is alive is to look for the hinged intruders, thus protecting the algae plates. If the supply from shell is really SIMPLE PRECAUTIONS grazers (other empty (you than itself, of have to look It is important to remember that for all its beauty, this is course). What is closely), the not an amusement park. No one has tailored this environ- really neat is ment to be risk-free. It is not up to code. animal is dead. For instance, on land we generally take traction for how it Along this granted. We assume that, except for very rare instances, such differentiates stretch of rock as that massive cherry jelly spill down on Main Street, the between you should also surfaces we walk upon will be reasonably secure. In the competitors and find mound- rocky intertidal the opposite is true. You must assume that potential every surface from the A Little Further Down zone to the shelled limpets, water line is covered with cherry jelly. And the reason it’s so predators. When another kind of slippery is only partly due to the fact that things are wet. it encounters a snail, but often Many of the organisms on these rocks (particularly the algae) competitor (say not quite as are either slimy or very smooth. Either way, your tread must a smaller limpet high up in the be careful, considered and light. In general, walk on bare species) it pulls rock and aim for low spots even if it means getting your feet intertidal as the wet. Consider walking with one hand and both feet or even the front of its uppermost both hands and both feet; it will give you more stability. As shell against the periwinkles or far as footwear goes, I like rubber knee boots, but tennis rock and barnacles. shoes with plenty of tread are also good. Whatever you wear, bulldozes the Inevitably these expect to get wet, it’s just part of the ethos. offender out of On the other hand, it’s dangerous to get too wet; as in animals will be knocked over by a wave. This is amazingly easy to do, the territory. If it tightly bound to particularly when near the water’s edge and when you are comes upon a the rock; you inspecting something really fascinating. Always keep your predator (there probably will ears open for waves and check the sea frequently. In fact, it is are several not be able to best to be overly-cautious. When you first arrive, watch the kinds of snails surf for a few minutes to see what the wave action is like, remove them that will help dictate how close you want to go to the water. that eat limpets), with your bare And remember, incoming tides can bring waves in very the owl limpet hands. Rarely rapidly. raises up its will you see a Lastly, some tide pool etiquette. Never go tide pooling shell and slams limpet move alone. When you take your class, have students work in pairs it onto the foot or trios, with one person spotting for waves while the other about in the day looks in pools. Never turn your back on the ocean and never of the enemy. light; they run or jump. Keep the group within earshot of you and bring This causes the usually just sit at least one adult for every ten students. enemy to lose its there, probably hold on the rock asking each other koans as part of their and it often gets washed away by the next Zen meditation. In fact, most limpets are wave. nocturnal, they are active at night and While you are up in the rocks, try inactive during the day. If you go to the looking in the mounds of kelp which have intertidal at night (few people do, but it’s washed up on shore, particularly those really cool), you can see how active these around the high tide line. Often these snails can be. Like periwinkles, limpets have beach hoppers living under them. are algae-eaters, and they spend the night Beach hoppers are amphipods (another rambling over the rocks looking for food. shrimp relative), which live in sand

7 burrows during the day and come out at Sea stars begin here, and the lower night or when its cloudy. They feed on you go in the intertidal, the more kelp and other plant material. abundant they become. Sea stars are particularly common on mussel clumps, Little Further Down as mussels form a major part of their If you can get a bit further down the diets, along with barnacles, sea urchins, intertidal, there are many more kinds of and limpets. Sea stars are vastly organisms to see. You will still find intriguing animals, which probably play a periwinkles, limpets and barnacles, but major role in helping to decide what they may be different kinds (the barnacles animals are common in the intertidal. are usually bigger) and they have to Some scientists believe that if it were not compete with other organisms for space. for sea stars feeding on great quantities of Three large organisms are typical of mussels, these shellfish would eventually this habitat and they are often found cover most of the intertidal, excluding together. They are all also found further many other organisms. The sea star down in the intertidal. These are the species which are common in this high mussel, sea star (starfish) and gooseneck intertidal have thick, leathery skins, barnacle. So typical are these animals in which help prevent drying out at low this zone that it is often called the mussel- tide. sea star-gooseneck barnacle zone. Sea stars come in a rather becoming Probably the most obvious of the three is range of colors; red, orange, white and the mussel, a handsome black shellfish. bluish seem to be particularly common. Mussels are bivalves, those members of the And while five arms are the usual for phylum Mollusca which have two shells. many species, some may have fewer and Other examples of bivalves are clams, some may have as many as 24. Sea stars oysters and scallops. Mussels are usually walk and hold onto prey using tube feet, found where wave action is heavy. They tiny elongated suction cups which are anchor themselves to rocks (or any other found by the hundreds on the underside surface) using byssal threads, which are of the body. Using these feet, the animals very tough brownish hairs with glue on are able to walk over even wet, slippery the end, extruded by a gland in the surfaces with nary a hesitation, as well as animal’s foot. Mussels can withstand withstand the steady pounding by waves. considerable drying, closing up their Having selected a prey, say a mussel, the shells to prevent water loss. Small animal wraps its arms around the prey mussels, in little groups, are found high and begins to pull on the shells with its up in the intertidal, but the further down tube feet. Rarely is a sea star able to pry you go, the larger the mussels become open a mussel using only brute force. and the more massive the mussel clumps. Rather, as it maintains a steady pull Very often, mussels form aggregations of (which may last for hours or days), the hundreds or thousands of individuals, animal extrudes its stomach through its which solidly cover much of this zone. In mouth. This it slips through a minute turn, the clumps form a habitat for other space between the mussel’s two shells kinds of organisms. Some of these and begins to digest away the muscle organisms, such as worms and small holding the two shells together. Over crabs, live deep within the clumps, where time, the muscle is weakened, the shell is wave action is low. Others, such as pulled open and the sea star digests its barnacles, may attach themselves to the prey, then pulls the digested material into mussel shells. its mouth. Sea stars are very tough

8 organisms. They can regrow lost arms are completely harmless animals, they and, if an arm and part of the central body never pinch. When you pick up their are removed, this fragment will regrow a shells, the quickly retract, hiding away for complete new individual. a while. If you are patient, and hold them Interspersed among the mussels, or in steady in your hand, they usually come separate clumps are gooseneck barnacles. out and walk about, carefully inspecting Goosenecks do not resemble acorn the premises. It is likely that hermits are barnacles, but they are close relatives. incapable of actually killing a snail for its These well-named creatures have white shell, so they have to wait for shells to triangular plates attached to a long tough become available. This is a nerve- tube which is attached to the rock. When wracking task indeed, for as a hermit covered with water, the plates open up grows, it needs progressively larger and long feathery feet emerge, sweeping shells, so there is an eternal search for the water for small animals. Like mussels bigger and better homes. A hermit will and sea stars, goosenecks are pretty compulsively check out every empty shell resistant to drying out. At low tide they in its sight (as well as anything that might tightly close their plates and, with their be a shell), a process which involves leathery necks, are quite resistant to touching it, lifting it up and inspecting the desiccation. Goosenecks were originally insides. If the new shell looks good, a called “goose barnacles,” a name hermit will switch to it almost faster than popularized by John Gerard, a Sixteenth you can follow. Hermits spend a Century nature writer. Gerard, who remarkable amount of time “fighting” obviously knew how to tell a good story, with each other, apparently coveting their claimed he found birds ready to hatch opponent’s shells. No one seems to be from the shells of these barnacles. badly hurt from the experience, though Wandering around these various often the “winner” takes over the animals, or hiding in crevices, are a “loser’s” shell and the loser has to make number of rather pugnacious small shore do with the winner’s vacated split-level. crabs. When alarmed, which seems to be most of the time, they quickly scurry off, Further Down Than That running sideways or backwards. When Obviously, the difference between truly harassed, these animals raise their Further Down and Further Down Than That claws up in what must be the universal is a subtle and, really, quite artificial one. offer to “put up your dukes.” They are The reality is that as you go further down primarily scavengers, consuming into the intertidal, some organisms (the whatever is dead or dying. A mild ones that prefer to be dry part of the time) warning: handle with care, if at all, since become less common, then cease to exist, these crabs will give you a somewhat while others (the ones that like to be wet painful pinch. Sadly, this often results in most or all of the time) come into being more harm to the crab, by the startled and then dominate. Moreover, even tide-pool explorer, than vice-versa. within these zones, there will be Beginning in this zone, primarily in tide differences in environmental conditions pools, live hermit crabs. These are soft- and thus in what organisms are found bodied crabs which only live in the shells there. of dead animals, almost always snails of For instance, there is a difference some sort. In many intertidal areas, most between what occurs on open rock and of the snail shells will be occupied by what lives in tide pools. All of the animals hermit crabs, rather than by snails. These we discussed above can be found in tide

9 pools, but some others are only found in When the cells are touched (say by a small these pools. Probably the best examples fish or shrimp) the cells open, the whips are the fishes which occupy tide pools and toxin snap out and nail the prey. starting in the previous zone, but are far Quite quickly the anemone pulls in its more common in this one. In the higher tentacles, drawing the stunned or dead levels of the intertidal you will find prey into its mouth. If you touch an perhaps one or two species, while the anemone tentacle with your fingers, you very lowest intertidal pools may harbor can feel the whips hitting your skin, but 10 or 20 forms. It is usually very hard to only as a sticky sensation. The skin on spot these fishes, as they tend to be cryptic your fingers is too thick to be pierced. I or camouflaged, with colors and/or body had a teacher who once put his tongue on patterns which blend in with their an anemone (the skin of the tongue is surroundings. However, they do quite thin) and the class was quite taken periodically swim about, so stealing up to by the way the instructor danced about a pool and remaining very still for a few after the experiment. The swelling and minutes can be rewarding. discoloration only lasted a few hours. In general, sea urchins and sea There are several very intriguing anemones are more common in this zone exceptions to the rules about where than in the previous one and they are anemones and urchins live. For example, more common in tide pools than on the there is a very funky urchin open rock. Sea urchins are close relatives (Colobocentrotus) in the intertidal of of sea stars. Like sea stars, they have tube Hawaii which lives where heavy waves feet and their mouths are on the crash. However, it is specially adapted to undersides of their bodies. However, this environment, by having flat, blunt unlike sea stars, sea urchins are covered spines, which fold down over the shell by a hard shell (called a test) and by forming an almost smooth surface when spines. The spines, which in some species wave action is heavy. On the west coast are quite sharp and in others are rather there is a small green anemone, blunt, are movable. If you put a finger or Anthopleura elegantissima, which is very pencil against an urchin’s shell, it will common on open rock, often fairly high quickly move its spines toward the up the intertidal (a larger form is also irritation. Most urchins dine on algae, found in tide pools). This anemone forms scraping the stuff up with five small teeth huge colonies, and because it tends to (called Aristotle’s Lantern) circling their cover itself with broken shells and bits of mouths. Many sea urchins are easily gravel it often looks just like bare rock or dislodged by waves and some actually sand. Unless you are quite wary, the only excrete a chemical that helps them to way you may find them is when you step grind their way into their rocky homes to on “rock” and water oozes out. What is help escape from some of the waves’ most fun about this species is that an force. entire colony (which may have hundreds Sea anemones are relatives of jellyfish; of individuals and be a number of feet in a way they are like upside-down across) is composed of individuals which jellyfish which are attached to a surface. are clones of one another. In other words, The delicate flower-like character of an the colony started with one individual opened anemone belies the thousands of which budded off another, genetically stinging cells found in each tentacle. The identical, individual. Both of these microscopic stinging cells contain tiny identical anemones budded off others and whip-like strands and a potent toxin. so on. What happens when two colonies,

10 which are busily budding and covering a 2. If you roll over a rock (there can be boulder, meet? The individuals of one interesting things under rocks): colony can instantly tell that the A.Roll it over once, for the whole class. individuals of the other are not identical with themselves. Fighting erupts between B. Don’t keep the underside exposed too the colonies, with the anemones on each long, the creatures tend to be delicate. side touching the other with special C. Gently roll the rock back into the stinging tubes. If you look carefully at a same position you found it. rock containing two or more colonies, you will see an irregular line of bare rock 3. Don’t leave anything in the intertidal (often the only bare rock on the boulder) that you brought with you. which is a “no anemones land” where this warfare is occurring. Marine debris (garbage thrown away from ships and from shore) is a major Humans and the Rocky Intertidal problem throughout the world. It is not The animals in the rocky intertidal are only unsightly, but also dangerous to tough, but they are not immortal. We can many organisms. From turtles choking to damage and kill them easily, particularly death on pieces of plastic to seabirds when we enter their habitats. These throttling themselves on plastic six-pack organisms have evolved special rings, the extent of damage to marine adaptations for surviving in a very harsh organisms is large. We have a environment. But they have few defenses responsibility to ourselves and our planet, against human impact. Think about it this so you might even consider encouraging way. When we enter the rocky intertidal your students to do a mini-cleanup of the we become a part of that habitat. We are beach before you leave. just one more organism among the many. We have a responsibility to what is now (at least for the time we are there) our shared community. cs/lb 9/93 So we have to follow a few simple, but ultimately essential, guidelines:

1. If you pick something up: A.Pick it up gently. Don’t force or tear. B. Put it back where you found it. C. Put it back in exactly the position you found it.

What this means is that if you pick up a sea star (gently), do not take it home to die. And when you put it back, put it back in the same pool you found it. In most intertidal areas it is not only a bad idea to collect, it is also illegal without a special license.

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