|MadSci Network: Zoology|
Greetings! This was a great question. The following should explain everything you wanted to know about what happens to sea animals when the tide goes out. The information was taken from the Fitzgerald Marine Site located at http://www.sfgate.com/getoutside If the following does not satisfy your curiosity try going to the following sites. California boasts over 1,100 miles of coastline and with it some of the world's richest tidal life. http://www.dfg.ca.go v/watchable/tide.pools.html Tide Pools http ://web.calstatela.edu/facu...dit557/oceans/norma/otdpls.htm http://www.scr uznet.com/~rlandon/garrett/tidepool.htm Woods Hole's "Coastal Brief" series: Tide pools by Kimberly Amaral This is a map of plants and animals typically found in a Massachusetts tide pool http ://www.umassd.edu/Public/p.../KAmaral/Thesis/tidepools.html Oceans cover more than 70% of the earth's surface. Everywhere that the ocean meets the land, a unique and brutal habitat exists. Waves pounding at the rocks constantly reshape the coastline. In this narrow band between water and land, strange animals and plants thrive. Within the confines of the shore, tidal plants and animals have developed specializations which allow them to survive. The tidal zone is continually redesigned by three actions: wind, water and rock. Winds howl across the vast oceans which, over time, slowly erode the land as the waves crash against rocks stirred up by the wave action. Imagine pounding one fist into an open hand over and over again. This is life in the tidepool. When the tide retreats the sun beats down relentlessly. Exposed animals and plants need to conserve water to survive until the tide returns. Because the tides slowly invade and retreat, distinct sub-habitats exist within the tidepool, each with unique qualities. In the deeper parts of the tidepools, more water is present. Animals and plants that need constant moisture thrive in this zone. Animals and plants that need constant exposure to air live higher in the tidepool, where the waves simply splash. In between, unique critters straddle both worlds, surviving both in the air and underwater. The intertidal zone (the area between high tide and low tide) is rich with nutrients which are replenished by each incoming tide. As the waves crash down, they carry food necessary for survival of the tidepool inhabitants. Each wave carries a plankton soup which is the main diet of mussels and barnacles. Also, dead plants and animals wash into the tidepool feeding the numerous scavengers and opportunists, like hermit crabs, shore crabs, sea gulls and even anemones. Lifestyles of the Spineless and Slimy Shore crabs peek from protected rocky nooks as the tide slowly retreats. During the six-hour transition from high tide to low tide, sea stars search for mussel meals. Hermit crabs scavenge in shallow pools for food and new shell-homes. As the tide continues to drop, anemones close tightly, their flowery tentacles protected inside their jelly-like bodies. Limpets, periwinkles, and chitons wait for the tide's return to continue grazing on algae-covered rocks. At high tide, it's meal time. Plankton flows into the pools on each wave, feeding barnacles, mussels and worms. Seaweed, or marine algae, glistens through the waves, in bright greens, pinks, browns and reds. The watery world comes alive with fish, octopi, urchins, anemones, snails, crabs and sea stars. Most of the animals that live in the tidepools, or intertidal zone, are invertebrates; they have no backbone--they are spineless. Instead of a backbone, some animals have rigid exoskeletons that protect them from drying out, being eaten and being smashed to pieces by the pounding surf. Barnacles, sea stars, limpets, crabs, chitons and sea snails all have hard shells for protection. Anemones, sponges and nudibranchs have very soft and flexible bodies that absorb wave impact. When the waves crash it's not certain death, it's mealtime! Marine algae have developed similar characteristics as land-dwelling plants. They photosynthesize light and nutrients into sugar and oxygen. Many types of algae grow in the tidepools: green, brown and red. The color of the algae gives away their name. Marine algae contain a gummy substance, called agar, which allows them to be very flexible as the tides change. The leaf-like blades sometimes have small attached air sacs which allow the blades to float to the surface facilitating photosynthesis. Because of the changing nature of the tidepools, some areas get more water and others get more exposure to the air. As a result, plants and animals have adapted to each specific region: the splash zone, the high zone, the mid zone, and the low zone. During an ordinary low tide, the splash zone, high zone and part of the mid zone are exposed and accessible for exploration. Only during the spring and neap tides is the low zone exposed. During full and new moons, there are often very low tides which offer an excellent glimpse into this fascinating habitat. Some animals survive best exposed to the air, with only an occasional splash. In the splash zone, for example, animals find most of their food in the driest part of the tidepool. There are only a few species that live in this area. The next zone is the high zone, or supralittoral fringe. This is the upper limit the water reaches during high tide. Most of the plants and animals here need a minimum of exposure to water. Barnacles are common inhabitants of this region. Below the high zone is the mid zone, or infralittoral fringe. This is covered most of the time by water and receives exposure to air only during low tides. The most diversity is found in this region. The lowest part of the tidepool is called the low zone, or the infralittoral zone. Animals and plants live here that can survive a minimum of exposure to air. Urchins, abalone and brown algae are common. The Low Zone The low zone receives the most consistent amount of water. Only during the lowest tides is this area exposed to air. As a result, compared to other regions of the tidepools, low zone animals need the most water. Two of the most interesting animals found in the low zone are nudibranchs and sea urchins. Sea Urchins Purple sea urchins are common in the lowest part of the tidepool. They protect themselves from drying out by carving a hole in the rocks with their tough spines. Inside this little cave, the urchins are protected from crashing waves. During low tides, the holes fill up with water, providing necesssary moisture for their survival. To feed, the herbivorous urchins break off pieces of algae. They have rows of teeth located inside their mouths. Sometimes, the urchins grow too large to escape from this cave. To survive, they catch pieces of algae with their tube feet which can extend beyond their spines. Nudibranchs Nudibranchs are small, brightly colored slug-like creatures that live in the deepest parts of the tidepools. They have developed exposed gills (nudi=naked and branch=gill) which they use to breath underwater. Nudibranchs are carnivores that prey on sponges, bryozoans, hydroids and sometimes anemones. Those that eat anemones are unaffected by the anemone's stinging cells. They have developed a mechanism whereby they incorporate the anemone's stinging cells into their own bodies to defend themselves against being eaten. The Mid Tide Zone The mid zone is the most active zone in the tidepool. Many animals cross over and feed in this region as the tides change. Mussels, sea stars and anemones are commonly seen in this region. Anemones - Cousin of the Jellyfish Anemones, recognized by their flower-like shape, have stinging cells on their tentacles. Like their cousin the jellyfish, anemones paralyze their prey and draw them into their mouths to be digested. Anemones are carnivores and will eat just about any animal that comes close enough to be caught by its tentacles. Giant green anemones eat crabs, sea stars, mussels, limpets and fish. The smaller anemones eat small fish, shrimp and even plankton. Anemones have soft, jelly-like bodies that absorb the impact of battering waves. Most anemones, like barnacles, remain in one place for their lives. Anemones attach to the rocks with strong suction cups. Sometimes if food is scarce, they will let go and pump water through their hollow body (like the jellyfish) and move to a more suitable home. When the tide retreats, anemones close up their soft bodies, folding their tentacles inside to preserve moisture. When tidepooling, take care not to crush anemones. They can be well-camouflaged with small pieces of rocks and shells attached to their outside. Sea Stars Sea stars are a diverse group of spiny-skinned animals, related to sea urchins (echinoderms). The most common sea star in Northern California is the ochre star, which is usually orange, black or purple with a tough exterior. Leather stars, bat stars, six-rayed stars, sunflowers star and brittle stars are also present. Sea stars have a malleable exterior which allows them to wrap tightly around rocks' algae during tidal changes. Their internal hydraulic system allows them to cling tightly to rocks. They suck in water through their tube feet that run along their undersides, creating suction which they then attach to the rocks. This helps them stay connected during the roughest water. Sea stars have a fascinating method of eating. They are also carnivores, but they particularly enjoy mussels. The ochre star can often be seen during low tide just below a belt of mussels. As the tide retreats, the sea stars move across the mussel bed for a meal. They attach their strong feet along each of the two shells of a mussel. They then pull the shells apart. Once the shell is opened, even a fraction of an inch, the sea star starts to eviscerate its stomach (pull it outside its body). It then pushes the stomach into the shell of the mussel. The stomach contains strong digestive juices which it secretes to make a mussel milkshake. Chitons Chitons are pre-historic-looking mollusks. Their eight-segmented flat bodies are attached to the rocks by a strong foot. There are many types of chitons in Northern California, from the large gumboot chiton to the beautiful lined chiton. Chitons are, for the most part, herbivores. They graze on marine algae during high tide. They also have a scraping radula which shears algae from the rocks. Mussels Mussels, like barnacles, gather in dense clusters in the tidepools. Their blue-gray bodies contrast against the brightly colored sea stars that prey on them. Mussels are bivalves; they filter plankton from the water they suck into their bodies. An average-sized mussel can filter up to three quarts of water in an hour! Like many of the other animals in the tidepool, mussels remain in one place for their whole lives and they start their lives as plankton. As they mature, they begin to secrete a thread-like substance called a byssal thread. These byssal threads hold the mussels firmly to the rocks and other mussels. Once mature, mussels are unable to regenerate their byssal threads. The High Zone Many of the animals that live in the high tide zone have hard, flat shells to disperse the impact of the waves. Barnacles, limpets, crabs and snails thrive in this region. When the tide is in, they busily move around searching for food. When the tide is out, they must protect themselves from drying out, or dessication. All of the high zone animals have incredible abilities to stay attached to the rocks as the waves crash down. Crabs - A Tough Exterior Crabs, like all crustaceans, have a hard protective shell. The tough exterior can withstand crashing waves. Their flat shape allows them to squeeze into tight crevices, further protecting them from the waves and predators. Crabs can survive out of water for extended periods of time. As they wander around during low tide, they scavenge for bits and pieces of plants and animals. Crabs have five pairs of strong claws which allow them to grasp the slippery rocks. The first pair is noticeably larger than the rest. With these front claws the crabs can tear food from the rocks and pinch probing fingers. A large crab can easily break the skin and potentially break bones. Beware! Barnacles - Cousin of the Crab Barnacles are the most common inhabitant of the high tide zone. Although small and camouflaged, they cover tidal rocks by the hundreds of thousands. Like crabs, barnacles are protected by a hard shell. Unlike crabs, however, barnacles do not move once they reach adulthood. After hatching from eggs, barnacles are planktonic. They float around the oceans moved by wind and ocean currents. As they mature, they develop a glue-like substance on their heads. As a result, they become stuck by their heads to rocks. They eat by kicking the feather-like feet into the water to capture plankton. Limpets & Snails Limpets and snails are soft-bodied animals that produce a hard, often very decorative shell. They scrape algae from the rocks with their sandpaper-like tongue, or radula. Limpets and snails only graze while the tide is high. Limpets always return to the same place when the tide retreats. Some limpets carve themselves a place in the rock which perfectly fits their shells. This protects them from being eaten and drying up when the tide is low. The Splash Zone During high tide, crashing waves send salty mist onto the splash zone. This uppermost region of the tidepool is seldom covered by the ocean. Instead, it gets moisture from wave splash and rain. As a result, an interesting mix of plants and animals survive here. Land-based (or terrestrial) animals and plants survive here if they can tolerate some sea water. Marine animals and plants survive if they can tolerate exposure to air. As a result, relatively few tidal animals live in this zone. Terrestrial plants, like lichen, which can tolerate some salt water, are found here. Isopods, related to the pill bug, also scavenge in the splash zone for fragments of plants and animals. Thanks for taking the time to send in a question to the Mad Sci Network June Wingert Baylor College of Medicine Houston, Texas
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