Graphs: graphing/classic chartgo hohli
Nori seaweed belongs to the red algae genus Porphyra. It has membranous, olive to brown-purple fronds that grow up to 20 cm long. The fronds tend not to have a definitive shape, appearing like dark plastic sacks when exposed during low tide, and having a delicate, flimsy appearance when underwater. Nori grows on rocks in the mid to lower intertidal zone and prefers cooler water temperatures.
Nori is the most widely eaten seaweed in the world, commonly found in Japanese cuisine. There is a huge nori industry in Japan due to its commercial importance. For general information on the biology of algae, see the algae page.
Black pine is a member of the Neorhodomela genus: red algae that belong to the phylum Rhodophyta found primarily in the low intertidal zone. Black pine grows with spiraling fronds and reaches up to 20 cm in length, and often forms extensive mats of seaweed. Individual fronds resemble sprigs of pine trees and are dark purple to black in color.
A common species found along the Pacific coast of the U.S. is Neorhodomela larix, known as the black pine seaweed. Some Neorhodomela species can be used in traditional medicine as an anti-inflammatory agent or antioxidant. For general information on the biology of algae, go to the algae page.
Coral Weed (Corallina) is a widely-occurring red seaweed in the phylum Rhodophyta that is commonly found on exposed coasts. The alga consists of tough, calcareous, branching, segmented fronds up to 12 cm high which have a coral-like appearance.
It typically forms tufts long the rims of rock pools and in wet gullies in the mid to lower intertidal zone. Coral weed varies in color from purple to red to pink to yellowish. It deposits calcium carbonate within its cells to provide structural support and protect it against herbivory. Calcareous algae play important roles in the development and stability of coral reefs around the world. For general information on the biology of algae, see the algae page.
Mussels of the genus Mytilus are some of the most common bivalves mollusks in the sea. Mussels have blue-black shells and similar in appearance to clams and oysters. They attach themselves with fibrous threads to rocks and other large surfaces in the intertidal zone, or to each other to form extensive beds. Mussel beds protect individual mussels from wave action, can provide habitat for a range of invertebrate and algal species, are of commercial interest for shellfish production (mussels are a popular food) and as bait for fish, and are sometimes used as bioindicators. Both individual mussels and whole mussel beds are sensitive to temperature and chemical change, oil spills, and physical disturbance. They are therefore often used as indicators for pollution, and short and long term ecological change.
Mussels are filter feeders that eat a wide range of plankton. They actively pump sea water over their bodies with cilia both to breathe with their gills and to filter food morsels out of the water. They reproduce sexually via external fertilization and a larval stage that drifts in open water before settling on a substrate. Mussels are the favorite prey of other marine invertebrates including sea snails, crabs, and starfish. Mytilus mussels are found in intertidal zones throughout both the eastern and western coasts of the U.S. Mussels can tolerate a range of exposures from quiet, sheltered bays and salt marshes to wave-pounded rocky shores.
Acorn Barnacles of the genus Semibalanus belong to the group Balanomorpha and include some of the most commonly found barnacle species in the U.S. Acorn barnacles are normally between 2 and 3 cm long and are found at a wide range of depths from the intertidal zone down to several hundred meters.
One species of Semibalanus, S. balanoides, was studied as part of Joseph Connell's famous ecology experiment investigating competition in the intertidal zone in Scotland. For general information on barnacles, see the barnacles page.
Goose Neck Barnacles of the genus Mitella belong to the group Lepadomorpha. These barnacles tend to live in close clusters attached to rocks in deeper water than acorn barnacles. They are attached to the rocks by 3 to 4 cm long stalks, hence their name. Each time a wave washes over them, they strain food from the water.
Goose Neck barnacles feed mainly on small crustaceans and plankton. These barnacles were originally mistaken for molluscs due to their superficial likeness in appearance to clams and oysters. For general information on barnacles, see the barnacles page.
Whelks are predatory aquatic snails in the class Gastropoda. One of the more well-known species of whelk is the dogwhelk, also known as a dogwinkle. Whelks have distinctive conical shells, are between 3 to 8 cm long, and have very variable shape and coloration (the latter often depends on what they eat). All gastropods have a distinctive head, tentacles, and a long foot for locomotion. They move by generating a wave of muscular contractions that travels along the bottom of the foot, often aided by the movement of tiny cilia on the foot's surface.
Whelks occur on rocky shores and can tolerate a wide range of exposure, inhabiting both exposed areas and more sheltered coastlines. Whelks feed on bivalves, barnacles, and other marine gastropods. To eat their prey, whelks use a toothed, tongue-like appendage called a radula and an extendable proboscis. The whelk separates the shells of bivalves or drills a hole in a shell with its radula and then inserts its proboscis (dog whelks are often call oyster drills for this reason). The whelk secretes enzymes to partially digest the prey tissue and then sucks up the resulting soup. Dogwhelks reproduce sexually with internal fertilization. The females lay egg masses (called sea oats) attached to rocks in the spring. One of the more common species of dogwhelk on the Pacific Coast of the U.S. is the Frilled Dogwinkle, Nucella lamellosa (Gmelin).
Chitons are elongate-oval-shaped, marine molluscs. They can be up to 12 cm long with a shell made up of eight interlocking plates covered in a black or brown leathery girdle (which can appear green when algae grow on the outside). If you were to pick up a chiton and turn it upside down, you would see its flesh-colored gills and mouth and darker, orange muscular foot.
Image courtesy Phil Lambert, Royal BC Museum The most common chitons belong to the genus Katharina. Chitons cling to rock surfaces in the middle intertidal zones of rocky shores where they can withstand vigerous wave action. It moves around under water when feeding, but adheres itself tightly to rocks when the tide goes out. Some species exhibit homing behavior and return to the same spot on the rocks each time. Chitons feed on brown and red algae, and benthic diatoms which it scrapes from rock with its tongue (called a radula). Chitons reproduce sexually by releasing eggs and sperm into the water. Fertilized eggs develop into free-swimming larvae. The entire lifespan averages about three years. Species of Katharina occur all along the western coast of North American from Alaska to southern California. The most common species is K. tunicata (Wood), also known as the black katy or the black leather chiton. The genus name, Katharina, is named after Lady Katherine Douglas who sent specimens to zoologists at the Natural History Museum in London, England for description and examination.
The starfish Pisaster ochraceus, known as the purple (or ochre) sea star, is an echinoderm that normally has five radial arms and a body diameter of between 25 and 45 cm. Pisaster starfish can be a range of colors from purple to red to orange to brown, often depending on water temperature.
Pisaster is an opportunistic predator and scavenger that crawls along the rocky shore and in and out of rock pools hunting for prey. It feeds on a wide range of immobile and mobile marine invertebrates, including mussels, snails, limpets, chitons, and barnacles. Some mobile prey species have evolved the ability to chemically detect Pisaster in an attempt to avoid being eaten. On its underside, a starfish has rows of sucker feet that lead in towards a central mouth, of sorts, into which small prey can be engulfed. Like many starfish, to eat larger prey, Pisaster has a special stomach that can be extended, inside out, and inserted between the shells of crustacean prey. In this way, it prizes apart the shells and digests the tissue inside before swallowing it. On their dorsal side, starfish are armed with spines for protection. They also have what are called pedicellariae on the top of their bodies. These are tiny, stalk-like structures that can be extended with jaw-like pincers on the end. They can protect starfish from predation and also be used to grab onto small food items and crush them. Pisaster reproduces sexually by releasing eggs and sperm into sea water. Gametes form free-swimming larvae that go through several stages of metamorphosis before becoming adult starfish. Three species of Pisaster are found on wave-washed shores all the way along the western coast of North America, from Alaska to southern California. It is most abundant in the northeastern Pacific since it prefers cooler waters. Starfish are able to shed one of their arms to distract would-be predators. They can regenerate the arm that has been lost. In the past when starfish were considered a threat to commercial shellfish beds, fishermen removed them and cut them in half, effectively doubling the population due to the sea stars ability to regenerate. Starfish have been recorded living up to 20 years.
| Home | © Copyleft Peter 2.0 |