Grazers such as kelp snails, abalone, crustaceans and fishes feed on parts of living kelp plants. Detritus feeders like sea cucumbers, bat stars and lobsters feed on nutrient-rich decaying shed. Some animals, such as sea urchins, eagerly feed on the living plant and the shed.
They are considered to be both grazers and detritus feeders. Of course, as you investigate further up many food chains, you will discover a multitude of species that are drawn to the forests to prey upon the grazers and detritus feeders. As with all species of kelp, giant kelp reproduces through a procedure known as alternation of generations, in which a sexually reproducing generation alternates with an asexually reproducing generation.
Thus, the complete reproductive cycle consists of two generations of plants. During the s and early s men, both hunters and trappers, intensely overpursued the highly valued pelts of sea otters, hunting those mammals to the point of near extinction. Sea otters prey upon sea urchins, helping to maintain normal population sizes in healthy forest ecosystems.
Thus, with the demise of sea otter populations came a corresponding increase in the number of sea urchins. The unchecked expansion of sea urchins created intense competition for food among the urchins. While urchins normally prefer to feed on kelp shed, when competition for food increases, urchins will readily forage on kelp holdfasts.
When their holdfasts are weakened, kelp plants often get pulled free from the sea floor and perish. Once adrift, a given kelp plant frequently becomes entangled with other plants, tearing them away as well.
This chain of events severely threatened the very existence of a great many kelp forests. In sea otters in California waters became protected by law, and by the s and s were numerous enough to again control sea urchin populations in many areas.
During the same time period, conservationists began planting healthy kelp in deteriorating forests to supplement natural regrowth of kelp. In some endangered kelp beds where natural predators of sea urchins were rare, quicklime calcium oxide was utilized to decrease the numbers of grazing sea urchins. Owing at least in part to these efforts, many kelp forests made strong comebacks. With few exceptions, holdfasts are generally incapable of attaching to sand, mud or even silt-covered rocks.
The sewage created a layer of silt over the bottom, preventing new holdfasts from attaching, and as a result, thousands of square miles of kelp beds perished. Furthermore, as waste settles it can bury and kill tiny young kelp plants before they have a chance to establish themselves.
The layer of silt sometimes makes it difficult for new haptera to gain a grip on the substrate, making it even easier for tiny holdfasts to be torn from the sea floor.
In recent years Californians have become much more aware of the significant impact caused by sewage, and many communities have taken responsible action to prevent similar reoccurrences.
If anything positive is to be gained from this chain of events, it is an understanding of the vulnerability of the kelp forest habitat. Although they appear quite rugged, kelp forests can be quickly destroyed by overexploitation of the kelp or of many other vital members of the kelp community. Loss of the kelp forests would not only be a tragic waste of a beautiful habitat, it would deprive California of uncountable revenue.
If exploited without proper concern, kelp forests can be destroyed in very little time. On the other hand, if we protect this valuable ecosystem, California kelp forests can continue to provide economic resources, as well as home, food and shelter for many marine species, for years to come.
In Hollywood lore, kelp is often considered to be a man-eating monster, having the ability to reach out and entangle any swimmer or diver who as much as blinks while swimming through a kelp forest. With just a little common sense you can generally avoid even the slightest entanglement, but even if you do get caught in some kelp, it is quite easy to get free. Kelp is highly elastic, but it can also be broken easily. If you do happen to become slightly entangled, or if a fin buckle, console or tank valve gets hung up in a stipe, simply snap it in half in much the same way you might break a pencil.
You may need to bend it back and forth a few times before it snaps. If you do somehow manage to get really tangled in the stuff, a knife can help. Monitor your air supply so you can avoid having to pick your way over and through a thick surface canopy of kelp. Using your compass and paying attention to where you are can help you avoid unwanted surface swims. Plan your dive so that you ascend and descend at the edge of a kelp bed. Streamline your gear and secure gauges and hoses so you can avoid potential entanglements.
Finally, consider enrolling in a kelp diving specialty course. Beyond the purely esoteric value of its beauty, giant kelp has many other uses.
In the United States Department of Agriculture sponsored a study of the kelp beds, and since that time numerous industrial uses for kelp have been developed.
During World War I kelp was harvested and processed into potash and acetone for use in the munitions industry. Two of the more common types of branching coralline algae in bull-kelp beds are the genera Bossiella and Calliarthron. By March, these coralline algae are as lush as they will be all year. This makes them rather conspicuous, since just about all the other understory algae are either regrowing, severely battered, or missing entirely at this time of year.
Articulated coralline algae such as this one possibly in the genus Calliarthron are very common on rocks down to about 40 feet below the surface. Just as in a vertebral column, these segments are linked by a tough, fibrous central cord and protected from shock by thin pads that separate one segment from another.
The segments look even more skeletal when they turn white due to bleaching by the sun or fresh water. They may also turn white at the tips when reproducing, or when nutrients from spring upwelling events cause them to put on a late growth spurt Dawson Leafy red algae put on a growth spurt beneath bull kelp In addition to the coralline algae, leafy red algae form an important but more transitory part of the spring understory beneath bull-kelp beds. Unlike the red understory algae of giant-kelp beds, most of the leafy red algae that grow beneath bull kelp are annuals that live fast and die young.
Because they don't have to survive winter storms, these algae often have rather thin, delicate blades. The small, finely branched alga Cumathamnion decipiens , for example, first appears in Monterey Bay in late January, starts reproducing in April, reaches maximum size in May, and usually dies off by the end of June.
During its short growing period, the crenulated blades of Cumathamnion decipiens shelters an amazing variety of tiny organisms such as worms, nudibranchs, acorn barnacles, and skeleton shrimp Connor Fish and other animals colonize the kelp beds Like the understory algae, many kelp-bed animals are just beginning to recover from winter storms in March. For example, some kelp-bed fish move into deeper water during winter storms.
As storms become less frequent in March, they may begin to return to the kelp beds. Other fish, including the season's "first wave" of juvenile rockfish, give up their planktonic drifting to settle in or near the kelp beds during March. Many of these young fish rely on the red algae of the understory for hiding places and food. The newly arrived rockfish are voracious predators.
One of their favorite foods seems to be drifting larvae, especially barnacle larvae, which are common at this time of year. One study showed that juvenile rockfish can eat so many barnacle larvae that they reduce the number of barnacle larvae arriving in intertidal areas by up to 95 percent compared with coastal areas where rockfish are not present MBNMS Young kelp greenling enter the kelp beds A young kelp greenling, lurking near the seafloor.
After spending more than a year in open water, two- to three-inch-long juveniles typically appear in the kelp beds soon after the first major upwelling event of the spring MBA When they first enter the kelp forest, young greenling congregate within dense clumps of newly sprouted leafy red algae. These red algae provide the greenling with both food and shelter from larger fish, including others of their own kind CDFG Being one of the first fish to settle into the kelp beds provides several advantages for kelp greenlings.
Newly settled juvenile greenling eat a wide variety of food, including red algae, copepods, amphipods, and other small crustaceans. Once settled, however, they switch to eating other small fish--especially other juvenile fishes CDFG Because young greenling grow very rapidly compared with other fishes and are so well developed when they arrive in the kelp beds, they are much faster and stronger than the juvenile fish that enter the kelp beds later in spring.
This allows the young greenling to feed on the successive waves of young fish that enter the kelp beds over the next few months CDFG For example, in April or May, large schools of juvenile herring leave Elkhorn Slough and other estuaries. When these young fish enter the kelp beds, they are avidly consumed by the young kelp greenling. In late May or June, swarms of "second wave" juvenile rockfish settle into the kelp beds.
At this point, the young kelp greenling switch to eating nothing but rockfish. At other times of year, the rapidly growing greenling will eat whatever they can get their mouths around, including crabs, shrimp, snails, chiton, abalones, octopuses, fish, fish eggs, and algae CDFG Invertebrates colonize the growing kelp In addition to fishes, many kelp-forest invertebrates, such as crabs and snails, also begin to recolonize the kelp beds in March.
Some have spent the winter hiding out in rock crevices and kelp holdfasts. Brown turban snails , for example, spend the winter prowling the sea floor, but once the winter storms subside, they begin to crawl up the kelp, heading for the canopy in those areas where there is a kelp canopy.
The same may be true for kelp crabs , which first appear in kelp beds in February or March Iampietro As the kelp canopy expands during spring, so do the number and variety of animals that live there. However, the party in the kelp beds doesn't really get lively until summer, when the canopy is dense and many kelp-forest animals reproduce. Spring waves give the kelp a break At high tide in March, following a stormy winter, you may have a hard time finding any kelp beds along the Central Coast.
Source: Kim Fulton-Bennett. Sand beneath the kelp beds begins to move toward shore The smaller waves of spring may also cause sand from offshore bars to start moving back toward shore in some areas. Coralline red algae hang tough beneath bull-kelp beds One reason that the bull-kelp understory shows little seasonal change is because it is dominated by some of the most hardy perennial algae--the coralline red algae.
Pink sea cucumbers spawn Although summer is when many kelp-bed animals spawn, at least one animal is already starting to reproduce in March. This eager little creature is the pink sea cucumber Cucumaria miniata , which spawns primarily during spring phytoplankton blooms Langstroth and Langstroth Despite their name, "pink" sea cucumbers along the Central Coast are typically brick-red in color and live in cracks in the rocks below the low tide line, curving their ten-inch-long bodies and using their strong tube feet to hold themselves in place Morris They eat phytoplankton and zooplankton, which they capture using ten bright orange, sticky tentacles.
Pink sea cucumbers only extend their tentacles when feeding or spawning, both of which they do during phytoplankton blooms Langstroth and Langstroth During their spring spawning events, pink cucumbers put on something of an underwater ballet. When conditions are just right, all the cucumbers in a particular area stretch their bodies out as far as they can from their nooks and crannies and wave their tentacles, swaying from side and releasing clouds of eggs and sperm a process called broadcast spawning Langstroth and Langstroth The eggs and sperm float upward, sometimes forming a visible slick on the sea surface.
Because the eggs and sperm are concentrated right at the surface, most of the eggs are fertilized. In contrast, many other broadcast spawners, such as abalone, have very low fertilization rates because their eggs and sperm are dispersed as they drift within the water column Langstroth and Langstroth The pink sea cucumber's eggs and larvae are bright orange, which you might think would attract legions of hungry fish.
After the eggs hatch, the pink sea cucumber larvae drift for a week or two before settling back down to the sea floor Langstroth and Langstroth Since these planktonic larvae do not eat, they do not require phytoplankton for food, so it is not clear why they would be released primarily during phytoplankton blooms.
Perhaps these blooms provide the adults with the extra nutrition they need to spawn or coincide with other ocean conditions that help the larvae survive. Female sea otters teach their young to forage As in the open ocean, most of the spring changes in kelp-bed communities are invisible to humans aside from SCUBA divers.
With a pair of binoculars, however, even shore-bound humans can watch marine mammals such as sea otters as they go about their business in March. Sea otters mate and give birth all year long, but the majority of pups are born in mid-winter, from November to January MBA As befits a creature born in the middle of the storm season, baby sea otters are born with a "life vest" of thick fuzzy fur.
Although this fur won't let them sink, it also won't let them dive for food, so they are completely dependent on their mothers for food and protection. By March, some of the year's crop of young otters are already getting too large to nurse though that doesn't stop them from trying.
They have also shed their furry "life vests" for the sleeker coat that will let them dive beneath the waves for food. At this point, you can often see mother sea otters teaching their young how to hunt for food in the kelp beds MBA Adult otters often specialize in catching certain types of prey, such as clams or sea urchins.
Population sizes of many of these species, including some that are commercially important food species, depend on the success of kelp growth each year. Destructive fishing practices, coastal pollution and accidental damage caused by boat entanglements are known to negatively affect kelp forests. Area based management, such as the designation of marine protected areas MPAs , is an effective way to protect kelp forests from excessive use or harm by people.
Monterey Bay Aquarium. Marine Ecosystems Kelp Forests. Home Marine Life Marine Ecosystems. Distribution Worldwide in temperate to polar latitudes Physical Ocean Characteristics Cold, shallow, nutrient-rich, medium-energy waters Keystone Species Kelps, sea urchins, rockfishes, sea otters, seals Ecosystem Services Fisheries, ecotourism, kelp bio-products Share.
Some kelp species can measure up to 45 metres long. If living in ideal physical conditions, kelp can grow 45 centimetres a day. Kelp forests compromise one of the ocean's most diverse ecosystems.
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