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Exploring the beautiful nature of California
California Nature: Kelp Forest Ecosystem
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California's boundaries cover almost 156,000
square miles. It includes many diverse ecosystems including
redwood forests, kelp forests and Death Valley's deserts.
According to the California Chaparral Institute, the shrubland
ecosystem is the most prevalent ecosystem in California with
over 4 million acres.
An ecosystem encompasses all the living organisms and the
physical features of an area. It also includes the interactions
between them. An ecosystem stands apart from others because of
its dominant feature, for example ocean, desert, forest or
estuarine ecosystems. A habitat refers to a single population of
organisms within the ecosystem.
The kelp forests off the coast of Monterey Bay depict a
specialized ocean ecosystem. Brown algae, kelp, makes the trees
in this forest. Other organisms that live in the forest include
sea cucumbers, otters, abalone, blue rock fish and sea urchins.
Kelp grows fast and gets used in many products like toothpaste
and pudding.
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Kelp forests grow predominantly on the Pacific Coast, from Alaska and Canada to the waters of Baja California. Tiered like a terrestrial rainforest with a canopy and several layers below, the kelp forests of the eastern Pacific coast are dominated by two canopy-forming, brown macroalgae species, giant kelp (Macrocystis pyrifera) and bull kelp (Nereocystis leutkeana).
Giant kelp, perhaps the most recognized species of brown
macroalgae, forms the more southern kelp forests, from the
southern Channel Islands, of
California to northwestern Baja. Along the central California
coast where the distribution of giant kelp and bull kelp
overlap, giant kelp out competes bull kelp for light.
Instead of tree-like roots that extend into the substrate, kelp
has "anchors" called holdfasts that grip onto rocky substrates.
water's surface. Gas bladders called pneumatocysts, another
unique feature of kelp, keep the upper portions of the algae
afloat. A giant kelp plant has a pneumatocyst at the base of
each blade. In contrast, a bull kelp plant has only one
pneumatocyst that supports several blades near the water's
surface.
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Kelp forests grow along rocky coastlines in
depths of about 6 to 90 feet. Kelp favors nutrient-rich, cool
waters that range in temperature from 42 to 72 Degrees F. These
brown algae communities live in clear water conditions through
which light penetrates easily.
Kelp recruits most successfully in regions where the ocean
layers overturn, bringing cool, nutrient-rich bottom waters to
the surface and regions with continuously cold, high-nutrient
waters. Because the amount of dissolved inorganic nitrogen
decreases significantly in warmer marine waters, kelp
experiences reduced or negative growth rates in warm water. This
phenomenon is particularly evident in southern California where
giant kelp forests deteriorate in the summer months. Kelp
survival is positively correlated with the strength of the
substrate. The larger and stronger the rock on which it is
anchored, the greater the chance of kelp survival. Winter storms
and high-energy environments easily uproot the kelp and can wash
entire plants ashore. |
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Giant kelp is a perennial, living for several years, while bull
kelp is an annual completing its life cycle in one year. Both
types of kelp have a two-stage life cycle. They exist in their
earliest life stages as spores, released with millions of others
from the parent kelp, the sporophyte. The spores grow into a
tiny male or female plant called a gametophyte, which produces
either sperm or eggs. After fertilization occurs, the embryos
may grow into mature plants (sporophytes), completing the life
cycle.
Giant kelp can live up to seven years. Factors such as the
severity of winter storms may affect its life span. Growing it
the spring, it averages around 10 inches in a day, but can grow
as much as two feet in a day. The average growth of bull kelp is
around 4 inches in a day.
A host of invertebrates, fish, marine mammals, and birds exist
in kelp forest environs. From the holdfasts to the surface mats
of kelp fronds, the array of habitats on the kelp itself may
support thousands of invertebrate individuals, including
polychaetes, amphipods, decapods, and ophiuroids.
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California sea lions, harbor seals, sea
otters, and whales may feed in the kelp or escape storms or
predators in the shelter of kelp. On rare occasions gray whales
have been spotted seeking refuge in kelp forests from predatory
killer whales. All larger marine life, including birds and
mammals, may retreat to kelp during storms or high-energy
regimes because the kelp helps to weaken currents and waves.
Perhaps the most familiar image of kelp forests is a picture of
a sea otter draped in strands of kelp, gripping a sea urchin on
its belly. Both sea otters (Enhydra lutris) and sea
urchins (Strongylocentrotus spp.) play critical roles in
the stable equilibrium ecosystem. Sea urchins graze kelp and may
reach population densities large enough to destroy kelp forests
at the rate of 30 feet per month. Urchins move in "herds," and
enough urchins may remain in the "barrens" of a former kelp
forest to negate any attempt at regrowth. Sea otters, playing a
critical role in containing the urchin populations, prey on
urchins and thus control the numbers of kelp grazers.
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