THE KELP FOREST
A tropical rain forest comes to mind when we think of plentiful and interesting environments.
However, the kelp forests right off our coast rival rain forests in both abundance and
biodiversity. The kelp beds off the Piedras Blancas Elephant Seal Rookery are one of the
reasons that stretch of ocean was chosen to be a marine protected area. Over 800 animals,
from tiny one-celled creatures to whales, use the kelp forest as a home, refuge, nursery and
hunting ground. There are about 10,000 different kinds of seaweeds worldwide, broken down
into three main groups: red, green and brown. Only 600-700 seaweeds can be found in
California. Of the brown seaweeds about 20 of the largest are referred to as kelps. Kelp
forests, like the ones off our coast, occur in few places: ,the west coasts of North & South
America, small areas of South Africa, Australia, New Zealand and islands near the Antarctic.
Kelps along with all seaweeds are algae and as such are primitive plants with no root structure.
There is a holdfast that looks like a root system but is merely an anchor holding the plant to the
seabed. Nutrients needed for growth are absorbed by all parts of the plant directly from the
surrounding seawater. Giant Kelp (Macrocystis) has become the dominant species on the
central coast by out-competing other seaweeds for available sunlight. Giant Kelp has long
stems, called stipes, with blades attached along them. Where each blade attaches to the stipe
there is a float or pneumatocyst filled with gas that provides the buoyancy needed to lift the
blades closer to the surface and more sunlight. The blades use energy from sunlight along with
nutrients from the ocean in photosynthesis to provide food for growth. The stipes and the
attached blades are called fronds. There are 6-12 fronds on each plant and under ideal
conditions they can grow up to two feet a day, reaching a length of over 150 feet.
The reproductive cycle for Giant Kelp is similar to all seaweeds. There are specialized
reproductive blades called soporophylls that are attached just above the holdfast and have no
float. They produce spores of both male and female gender. These free floating spores attach
to the bottom and grow to become gametophytes. The female produces an egg that is
fertilized by the sperm from the male and starts to grow into the mature plant.
Giant Kelp is a perennial that can live up to 7 years; however changing environmental
conditions can affect its health, growth and coverage. Like most forests there is a growing
season for kelp. The springtime prevailing winds push the surface water down the coast but
because of the earth’s rotation the surface water ends up moving offshore. This phenomenon,
called the Coriolis Effect allows subsurface water with all its stockpiled nutrients to come to the
surface near the shore. This water shift, called upwelling, along with the longer days of
abundant sunshine cause a growth spurt in the kelp forest. The fall brings lighter winds,
shorter days and slower growth. The storms of winter can bring large wave action that will
dislodge holdfasts. After strong storms we often see huge piles of seaweed on the beach. An
overabundance of herbivores like the sea urchin can also deplete kelp beds. Sea otters eating
sea urchins provide one of the balances needed for a healthy kelp forest and are considered a
keystone creature for that environment.
Besides being a very important ecosystem, the kelp forest is also of great economic value.
Algin, extracted from harvested kelp, is an emulsifying agent used to keep combined liquids in
suspension and make them smoother. Over 500 different products from pharmaceuticals and
lotions to paints and beer have algin in them. It is likely that not a day goes by that we don’t
use something with seaweed in it. The abalone farm north of Cayucos leases the kelp beds off
the Estero Bluffs from Fish & Wildlife and pays a per pound harvest fee for gathering kelp to
feed its abalone.
Bull kelp
Giant kelp
(Nereocystis)
(Macrocystis)
float
stipe
blade
blade
frond float
stipe
growing
frond
holdfast
sporophyll
(lacks float)
Bull Kelp:
Annual.
A type of brown algae.
May grow to 100 feet or more.
Often mistaken for sea otters.
All blades fertile.
Fertile areas darker than the rest
of the blade, eventually fall off
leaving holes.
holdfast
Giant kelp:
Perennial.
Can live for 7 years and grow to over 100 feet.
Each stipe with blades lives 3-6 months.
A type of brown algae.
Important habitat for many types of sea life.
Fertile blades (sporophylls) near holdfast
lack floats.
Important commercially as a source of algin
used in many products: toothpaste, beer,
ice cream, salad dressing, paint, etc.
Spores of both kelps grow into separate microscopic male and female gamete producing algae.
The union of egg and sperm forms a zygote.
Kelp Photos
Giant Kelp
Holdfast & Reproduc ve Blades
Giant Kelp
Feather Boa
Turkish Towel
Bull kelp
Oar Weed