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Bird Rock Tide Pools

The tide pools at Bird Rock in San Diego are very easy to get too and have lots of diversity. There are two main large rocks that are the most interesting. Look at the sides of the rocks and visitors will see thousands of small depressions that hold chitons, limpets and sometimes smaller anemones. There are plenty of solitary sea anemones and a few big Owl limpets. The larger rock farther out has more to see but a bit more difficult to get to. Both the large rocks have lots of marine life to see attached to the sides.

Location and Tameness

The tide pools start at the base of the stairs and extend out about a hundred yards. Park anywhere along the streets. The stairs leading to the tide pools is located at the end of Bird Rock street. There are no restroom facilities. There are a few restaurants nearby.

Bird rock is a single large rock that forms a small island when the tide is high and is located at the end of Bird Rock Street in San Diego. This is a popular surf location when conditions are just right. The tide pool area can be accessed by the stair case at the end of the road. At the base of the stairs, there are large boulders that have lots of smaller limpets pretty high up. This will give an indication about how high the tide reaches as these animals tend to live in the mid to upper tide zone.

The flat area between the staircase and bird rock is covered by mats of coralline encrusting algae. This area also has sporadic sea anemones usually covered by tiny bits of shells to prevent them from drying out. Continue walking out to the large rock and notice the thousands of small depressions in the base of the rock. At the bottom of each depression, there is usually a chiton living at the bottom. These animals will sometime form these depressions using their radula when scraping for algae.

This area is also a great location to see the different animals that live in the different tide zone. Starting from the bottom, there is lots of algae covering the rocks. The next higher zone is covered with the depressions and chitons. Limpets will also live in this area. The next higher zone is where barnacles and small snails live. This location used to have a lot more diversity but has suffered from too much human impact.
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Animals in Tubes

Tube worm colony
Closeup of Tube worm colony Tube worm colony A couple of Tube worms starting a colony Close up of tube worm opening. Notice head of animal in tube Close up of tube worm with head partially extented

Tube Snail (Serpulorbis squamigerus )

These animals have long tubes sometimes several inches in length. The tubes are light in color and can form colonies of multiple individuals. They tend to live in protected locations with high water flows. These animals are types of snails and are not worms.
Typical sand castle worm colony in protected high water flow area
Single Sand Castle worms attached to rocks. They usually settle next to other individuals but not always Large Sand Castle worm colony More examples of Sand Castle colony Sand Castle worms need plenty of sand and moving water Sand Castle worms compete with many other life forms for space

Sand Castle Worms (Phragmatopoma californica)

These animals are worms similar to the common garden worms. They build tubes made of sand that are glued together by special proteins. This glue is unique in that it hardens in water. These proteins are being studied for possible commercial use. These worms form large colonies and only live near areas where there is lots of sand and fast moving water.
Dodecaceria creates large colonies of animals.
The shells of the animals will fuse together creating a single, large structure

Other Tube Building Animals

One of the more common worms in this category is Dodecaceria fewkesi. These animals form large colonies that look like rocks with small holes. The shells or casings of the worms will fuse together forming a large coherent structure. They are filter feeders and use specialized appendages to capture plankton from the water flowing by.
Description – Worms in this sense means animals that have long cylindrical body forms that have some sort of hard outer shell or form of protection. Animals in this group are true works and other are related to snails (mollusks). The animals live in their shells or homes and extend feeding parts into the water to feed. They also live in very different areas in the tide pool location.

Feeding – Many of the worms, like animals in the tide pool environment, feed on small planktonic plants and animals suspended in the water. The tube worms will create a net made of mucus that traps the plankton as the water moves by. The mucus net is then moved to the mouth and eaten by the animal. Sand castle worms have special appendages they use to trap plankton as the water moves over the top of the animal.

Protection – These animals all make some sort of shell or covering as a form of protection. Tube worms make a hard outer shell similar to the shells of clams and mussels. Sand Castle worms on the other hand make their homes by gluing sand grains together to create a tube. Both the shells and the sand tubes provide some sort of protection from both the environment and predation.

Ecology – Tube worms like other mollusks have different life stages. They start out as eggs and morph into larvae that float in the water column. The larvae will then settle down on a preferred location. Sand castle worms are gregarious in that that will tend to settle next to other individual of the same species. This in turn creates large colonies with hundreds of animals. Tube worms are similar but the number of animals in the colonies is less.
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Sea Urchins

Lone Purple sea star
Purple sea stars in bottom of pool Sea stars have a hard test or shell. This is what many visitors find in tidepools Lots of sea urchins living in pool Sea urchins lying along cracks in bottom of pool Sea urchins will stay in the same pool for long periods of time and sometimes their whole life Lots of sea urchins living in pool

Purple Sea Urchin (Strongylocentrotus purpuratus)

The purple sea urchin is the most common sea urchin visitors will see in the tidepool. They have an unmistakable purple color. They are covered by hundreds of spines and tube feet. They are typically a few inches in width an found in pools of water. They prefer to be submerged all the time but on occasion will be caught above water as the tide reseeds.
Red urchin with smaller purple urchins
Deep red colored urchin with smaller purple urchins

Red Sea Urchin (Strongylocentrotus franciscanus)

Red sea urchins range in color from a strong red to a very dark red almost black color. They are a little larger than the purple sea urchins and found in the deeper parts of pools. They are not very common so find one can be tricky. They feed on algae similar to the purple sea urchins.

White Sea Urchin (Lytechinus anamesus)

White sea urchins prefer deeper and cooler waters. Adults appear light brown with white and brownish spines. They are not as common as the purple sea urchins and not quite as large. They feed on algae and diatoms.
Description – Sea urchins are very unique animals in that their bodies are covered with spines. The spines serve multiple purposes including protection, feeding and making a home. Urchins have a hard outer shell called a teste. Spines are attached to the test along with tube feet. Urchins like sea stars have many tube feet that they use for feeding and moving. The spines are different lengths. Contrary to popular believe, they do not have an venom in the spines.

Feeding – Urchins are herbivores and primarily eat brown algae. They will spend most of their lives sitting on the bottom of the ocean or pool waiting for algae to get caught on the top of their spines. The urchins, using their tube feet will move the algae from the top of their shells to the bottom where the mouth is located.

Protection – The spines of an Urchin are the most obvious form of protection. They prevent the smaller and sometimes larger animals from preying on them. Urchins also have a hard shell that spines are attached to that also help protecting the animals.

Ecology – Urchins will spend most all of their time sitting on the ocean floor or bottom of a tidepool. They sometimes create a home scar that is a small depression in the rocks. The home scar is created slowly over time as the urchin will move around on the same spot and the spines slowly erode the rock. Urchin also can venture out away from their home scar or preferred location when food becomes scares. Urchins have been known to migrate in mass and look for additional food sources. During this movement, they can devour most all plant live in the area.
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Snails

Group of three Black Turban snails
Two larger Black Turban snails with smaller periwinkles Numerous Black Turban snails that appear lighter in color due to bleached algae on shell Single Black Turban snail in sand Black Turban snails will frequently aggregate in shallow cracks and depressions at low tide Black Turban snails will frequently aggregate in shallow cracks and depressions at low tide

Black Turban Snail (Chlorostoma funebralis )

Probably the most common larger snail found in tide pools. The shells are typically about ½ - 1 inch in diameter. The lower part of the shell is black and the top part of the shell is a light brown or white color. They feed primarily on algae and found in the mid inter tidal zone.
Smaller periwinkles in group of barnacles
Periwinkles can be very small Periwinkle like other snails will aggregate in small cracks and depressions at low tide Periwinkle like other snails will aggregate in small cracks and depressions at low tide - close up view Periwinkle snails feeding on algae in small pool Periwinkle snails aggregating in cracks of rocks to prevent drying out

Periwinkle (Littorina spp.)

This is a very common snail found in the upper intertidal zone. They are small, less than ¼ inch and feed on micro algae that grows on exposed rocks. They can sometimes be hard to see as they are so small.
Wavy Top Turban snail
Wavy Top Turban snail

Wavy Turban Snail (Astraea undosa )

This is the largest snail found in the inter tidal zone. They are frequently found on sand in shallow areas as well as on rocks. They are herbivores and feed on various types of algae. Not as common as other snails and most visitors find the shell and not the living animal.
Small welk on rock
Two hermit crabs using welk shells Predatory snail Predatory snail

Predatory Snails

There are several different types of predatory snails ranging from welks, murex, horn snails and dog emarginant dog winkles. These snails are characterized by having the spiral of the shell more horizontal oriented than vertically oriented. These snails will slowly move around the tidepool areas looking for mussels, barnacles and other shelled animals to feed on.
Kelp snail on mussel
Kelp snail Kelp snail feeding on brown algae Kelp snail with several barnacles growing on shell

Kelp Snail (Norrisia norrisi )

A very colorful snail typically with an orange colored shell. They usually live in deeper water and feed on various brown algae. They can be seen at very low tides in the larger brown algae communities. They have a bright orange/red foot and green under part of the shell.
Description – Marine snails have two distinct categorizations. They are the herbivores ( plant eaters ) and the carnivores ( animal eaters ). These two categorizations also have similarities in the body type. Herbivores tend to be more round and have the shell spiral oriented upward whereas carnivore shell types have the spiral more horizontal.

Marine snails are very similar to the snails you have in your backyard except they have gills instead of lungs. They have a hard outer shell, a large foot that is used for locomotion, mouth and eyes typically located at the end of eye stalks

Feeding – Snails have two types of feeding behaviors. The first group feeds on algae. This is either the larger visible macro algae or also the smaller, less visible micro algae. . Most also have a radula that is a specialized feeding apparatus that has a sharp tooth at the end. The snail uses this to either scrape off algae on rocks or drill an hole in an animal’s shell.

Protection – snails have a variety of adaptations that protect the animal. The first and most obvious is the hard outer shell. The shell protects the animal from wave action and predation. Snails also need to protect themselves against drying out when exposed to air. They have an operculum that is used to tightly seal the entrance of the shell making it water tight.

Ecology – Snails will venture out onto the rocks and sand when the tide is high to search for food. When the tide lowers, they will commonly seek the shelter of pools or cracks where they have a lower chance of drying out.
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Chitons

Conspicuous Chiton
Conspicuous Chiton

Conspicuous Chiton ( Stenoplax conspicua )

These chitons have shell plates that are more regular and straight. The plates appear as light grey with hints of blue color. They can grow quite large. Adults can grow to 3-4 inches in the right conditions. They are typically found under rocks or at the bottom of shallow pits and holes in rocks.
Spiny Chiton
Spiny Chiton Spiny Chiton Spiny Chiton Spiny Chiton are often found at the bottome of small holes in rocks Spiny Chiton Spiny Chiton

Spiny Chiton ( Nuttallina fluxa )

The spiny chiton is the most common chiton in Southern California tide pools. They girdle or fleshy part on the rim of the animal is frequently covered by algae and sometimes will cover the entire animal. Spiny chitons are found in the mid to lower tidal areas that are less exposed to wave action.
Description – Chitons are marine mollusks similar to snails and limpets in that they have a single shell on the top of the animal and a fleshy foot on the bottom. Chitons also have a set of plates that make up the upper portion of the animal whereas limpets and snails have a single shell. Chitons blend very well in the environment and can be hard to see at times.

Feeding – Chitons will move along the rocks grazing on various types of algae. They have a radula similar to other snails that they use to scrape off the algae on rocks. Chitons will feed on a variety of algae including coralline, red and brown algae.

Protection – Chitons rely on their strong shell plates for protection from wave action and predation. They can cling tightly to rocks and survive on wave exposed areas. Common predators include seagulls, sea stars and the occasional lobster.

Ecology – Chitons become more active as the tide increases. They will leave their home and move around scraping algae off rocks. Some chitons have simple eyes they can use to distinguish between light and dark.
Sea star with urchins and anemones

Sea Stars

Loan Ochre sea star on rock
Ochre sea stars feeding on mussels Ochre sea stars feeding on mussels Ochre sea stars feeding on mussels Ochre sea stars have different color variations Single Ochre sea star feeding on mussel Purple Ochre sea star near similar colored algae Ochre sea stars exposed at low tide

Ochre Sea Star ( Pisaster ochraceous )

This is the most common sea star in the tide pool environment. These sea stars appear in a variety of colors including orange, browns and purple. They live in the lower inter tidal zone and almost always found near mussel and barnacle beds. They may appear higher in the tidal zone wedged inside cracks and nooks where they can preserve moisture and stay cool. When the tide is high they will start moving around looking for food. It has been estimated that an adult Ochre sea star will eat about 80 mussels in a year. Adults are usually between 8-12 inches but larger specimens can be found.
Multicolored bat star in aquarium
Pink colored bat star Bat star exposed at low tide

Bat Star (Patiria miniata)

The Bat star is easily recognizable in that the arms are connected by a web. They also come in a variety of colors ranging from orange, red, purple and others. They are frequently molted and may have more than one color. Bat stars are omnivorous in that they will eat both plant and animals. They are fairly common in the lower inter tidal zone.

Brittle Star (Amphiodia occidentalis )

Brittle stars have five arms as other sea stars but the arms are much thinner and longer. They also can use these arms for movement whereas other sea stars rely on their tube feet for moving. This species of brittle star is usually a brownish to darker brown color and found under rocks in the lower tide zone.
Giant sea star in aquarium
Giant sea star Close up of Giant sea star arm Close up of Giant sea star eye spot ( red area on tip of arm )

Giant Sea Star (Pisaster giganteus )

The giant sea star ( aka Knobby Sea Star ) is typically brownish to darker brown with lots of short spines that are white with blue rings at the base. This sea star gets its name in that the spines are larger than most other sea stars. Knobby sea stars can grow up to two feet in diameter. They are rarely seen in the tide pools as they typically live much deeper and like to live near kelp forests. They feed on a variety of mollusks.
Pink sea star in aquarium
Pink sea star in aquarium

Pink Sea Star (Pisaster brevispinus)

The pink sea star ( aka short spine sea star ) is another larger sea star rarely seen in the tide pools. Larger specimens can reach 2 feet in diameter. They typically live in much deeper water and feed on clams and mollusks.
Description – Sea stars belong to a group of animals that call Echinoderms. This translates into spiny skin. Sea stars have hard outer skin with many short spines or bumps (ossicles) on the top part of the animal. Sea stars usually have 5 arms that radiate out from a central body. They have tube feet that are used to catch prey and move around. The coloration of sea stars varies between species as well as the body form. Sea stars are typically found in the lower tide pool region.

Feeding – Sea stars are carnivorous in that they feed on other animals. They can use their tube feet to attach to the shells of mussels and barnacles and pull the shells apart. Sea stars then invert their stomachs into the opened shell and digest the prey from within their own shells. Sea stars are incredibly strong and only the largest mussels and barnacles can withstand an attack.

Protection – Sea stars have a combination of physical and behavioral protection strategies. They have hard outer bodies the can withstand most attacks. They can cling to rocks and other substrate using their strong tube feed to withstand predation from sea gulls and sea otters.

Ecology – Sea stars are characterized by having hundreds of tube feet. These tube feet are used for locomotion and feeding. Some sea stars like the Ochre have small eye spots on the tips of their arms. These simple eyes can distinguish between light and dark and may be used to determine shady locations and time of days. Several sea stars have multiple stomachs that can be extended into their prey animals.

Ochre sea stars can live for over 20 years in the right conditions. The adults periodically release eggs and sperm into the ocean where fertilization takes place. The juvenile sea stars spend several weeks in the open ocean before settling on a rock or other substrate. The juveniles then transform into the adult form and begin to grow.
One of the numerous sea hares found in the lagoon area

Sea Hare

Sea Hare feeding on algae
Sea Hares are very well camouflaged California Sea Hare California Sea Hare California Sea Hare

California Sea Hare (Aplysia californica)

This is the most common sea slug found in the inter-tidal region. They prefer to graze on specific kinds of red algae. The pigments in the red algae contribute to the overall coloration of the sea hare. These sea hares are particularly difficult to see as they blend into the environment very well.

California Black Sea Hare (Aplysia vaccaria )

this is the largest of all sea slugs. They can grow upwards of 15-30 pounds. They feed on various brown algae in deeper water. They are not commonly seen in tide pools but they can be seen on occasion.
Sea Hare feeding on algae

Navanax ( Navanax inermis )

This sea slug is predatory in that it feeds on other sea slugs, nudibranchs and some snails. The body is generally dark in color with thins blue and orange lines. The body has small white spots. Navanax is typically only a few inches long and found in the water in the lower parts of tide pools, kelp beds and areas with sea grass.

Navanax will track its prey using its keen sense of smell ( chemoreseptors ). The animals will encounter a chemical trail left by a sea slug or other prey item and follow it until it loosed the sent trail ore catches the animal.
Description – Sea Hares are related to snails ( mollusks ) except they do not have an outer shell. They are just like the common garden slugs that devour your backyard plants. The main difference is that they have gills rather than lungs. There are between 60-80 thousand types of mollusks that have been identified. Only three of these are sea slugs commonly found in California tide pools.

Feeding – Most sea slugs feed on specific types of red and brown algae. They use their radula ( sharp mouth parts ) scrape off the algae to feed. Navanax is the only local sea slug that is predatory and feeds on other animals.

Protection – The California Sea Hare has several types of defense mechanisms. The first method of protection is camouflage. It looks very similar to the algae it feeds on and is difficult to see unless it is moving. The second defense mechanism for the California Sea Hare is it can release two types if ink. The first type of ink is a dark purple colored ink similar to squid and octopus. The second form of ink is white in color and will confuse the predator into thinking it is full or no longer hungry. The black sea hare does not have the capability to produce ink.

Ecology – Sea hares are usually short lived and typically life less than a year. They are hermaphrodites in that they are both male and female. They can reproduce sexually when they encounter other animals.
Many channels intersect the rocky area creating good tidepool habitat

What is a Tide Pool

What is a tidepool? What makes a good tidepool? Tidepools are rocky areas that trap seawater in small pools, cracks and channels as the water rises and lowers based on the tides. As the sea level lowers, a pool of water is trapped for a period of time. When the seawater rises, the areas are flooded again and the cycle continues. These pools of water created by the tides are aptly named “tide pools” as they are pools of water created by the tide.

Tidepools may also be considered as any part of the intertidal zone where there are rocks and other substrate for plants and animals to attach too. The intertidal zone is the area between the upper limit of the tide and the lower limit of the tide. Sandy beaches are not considered as tide pools as there is no hard surface for plants and animals to attach on too.

Life in a tidepool environment can be very hard and hazardous. Plants and Animals are continuously exposed to very harsh conditions. Marine life that lives in this environment is subjected to very harsh physical conditions. These conditions include huge waves that continually pound the plants and animals, constantly being submerged in sea water and then exposed to air, rapidly changing temperatures both in the water and air and quickly changing saltiness or salinity of the water. These are called abiotic factors or non-biological factors.

Plants and animals living in tidepool areas are also subjected to a variety of biological related pressure. These include predation from other animals, competition for living space, competition for food and human impacts. These are referred to as biological or biotic factors.

When exploring the tidepool environment visitors will begin to notice certain patters. These patterns include the distribution of animals in certain locations, similarities between adaptations of the animals and even the absence of marine life in certain locations. After spending some time observing this amazing environment, these patterns become more apparent.

At first glance, these patterns may appear random. These patterns and why these patterns form are anything but random and most have very interesting explanations and reasons why they form. We learned that there are two groups of challenges marine life must overcome when living in a tidepool. They are physical and biological factors. But why would any plant or animal want to live in this environment in the first place.

To understand this question and the answers, we must acknowledge two basic driving forces about these plants and animals. The first driving force is they will try to eat as much food as possible. The second driving force is they will want to prevent themselves from being eaten or killed. The goal for all marine life is to perpetuate their species by having offspring. The reason why animals live in tide pools in the first place and why the patterns in tidepool ecology exist is the result of the interaction between these two driving forces and the physical and biological factors described earlier.

As visitors explore the tidepool area keep in mind the challenges marine life faces in this environment and try to think about the adaptations these plants and animals have that allow them to overcome the physical and biological factors and ultimately survive.
Hopkins Rose Nudibranch

Nudibranchs

Two Hopkins Rose Nudibranchs with a Spanish Shawl
Hopkins Rose on algae looking for bryozoans Hopkins Rose

Hopkins Rose (Okenia rosacea )

The Hopkins Rose Nudibranch is very easily identified as the whole animal is pink in color. This Nudibranch is usually about an inch long. The body is covered by drooping spines that resembles a shaggy dog. This nudibranchs feeds almost exclusively on another very small marine organism called Bryozoans. These are really small animals that form colonies similar to coral.
Two Hopkins Rose Nudibranchs with a Spanish Shawl

Spanish Shawl (Flabellina iodine)

This nudibranch is also easily identified as it has a bright blue/purple body with orange to yellow appendages ( cerata ). This animal is usually about 1-2 inches in length and found in pools of water closer to the ocean. This animal feeds exclusively on a single species of hydroid a very small marine animal. Spanish Shawls have an interesting defense mechanism. They will swim or flutter away if they are threatened. This swimming however is slow but can be effective against even slower moving predators like the predatory sea slug navinax.
Description - Nudibranchs are marine mollusks similar to the snails and slugs found on land. Nudibranchs are unique in that their gills are located on the outside of their bodies. Most all other slugs have their lungs on the inside of their bodies. Nudibranchs come in a wide variety of colors and sizes. Most Nudibranchs are brightly colored and between one and a few inches long.

Feeding – These two nudibranchs are very finicky eaters in that they only eat a very specific type and species of marine animal. They will slowly move around the tidepools searching to the one species of animal they will consume. It is interesting to note that each type of nudibranch will feed on a different marine organism.

Protection – Nudibranchs have a variety of protection mechanisms. The most interesting method of protection is they have stinging cells in the cerata ( appendages on the outside of their bodies ). Nudibranchs don’t actually make or grow these stinging cells themselves but actually reuse the sting cells from the animals they eat.

Nudibranchs are also brightly colored. This may seem odd for an animal trying to hide from predators. The bright colors however serve as a warning to potential predators indicating they are not as tasty as the predator may initially think. Paste experiences with these foul tasting nudibranchs are often all that is needed to deter any predator.

Ecology – Nudibranchs are marine mollusks similar to the snails and slugs found in your back yard. They have lost their shell for the most part but essentially have similar body structures. Nudibranchs spend most of their live slowly moving around the tidepool area looking for food. Hey are hermaphrodites in that they are both male and female. They can essentially reproduce by themselves or mate with other nudibranchs if available and conditions are right. They have a short live span typically less than a year.