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FOSS Ecoscenarios: Monterey Bay National Marine Sanctuary
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INTRODUCTION
Biome: Kelp Forest
The Monterey Bay National Marine Sanctuary (NMS) stretches along the coast of California,
from San Francisco to Santa Barbara.
The sanctuary protects an area of unique biome known as the kelp forest. Here, kelp grows great
heights from the rocky seabed to the ocean surface. This marine forest is home to rich marine
biodiversity, including fish, sea otters, and many marine invertebrates.
iStockphoto/mpiotti
Monterey Bay is one of 13 national marine sanctuaries.
In the 1800s Americans recognized the need to protect certain areas of the United States from
development, and to preserve them in their natural state. This led to the establishment of
Yellowstone National Park in 1872, the US Forest Service in 1905, and the National Park Service
in 1916. However, the oceans and coastal waters were not included in either of these systems. It
was not until 1969, when a huge oil spill devastated the coastline of southern California, that the
need to protect North America's coastal waters came to public attention.
The National Marine Sanctuary System was established in 1972 as a division of the National
Oceanic and Atmospheric Administration (NOAA). A national marine sanctuary is like a national
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park in the ocean. The sanctuaries protect marine habitats and local cultural history. Activities like
dumping waste and drilling for oil are not allowed. Activities like fishing and recreation are
permitted but regulated. Monterey Bay NMS was established in 1992. It is the largest national
marine sanctuary, covering 13,730 square kilometers (km2).
In the 1800s, kelp farmers wrapped cables around large areas of kelp to pull it up for use.
However, this practice prevented the kelp and its surrounding community from growing back
quickly. Today, kelp is harvested by cutting the stipes (stems) about 1.2 meters (m) below the
water’s surface. This way the holdfast (root-like structure) and most of the stipe remain intact.
The kelp regrows quickly and can be cut again later.
Monterey Bay NMS offers many ecosystem services. Kelp is a source of algin, an ingredient in
foods and other household products. In the sanctuary, kelp is harvested by hand to make food for
farm-raised abalone. Kelp forests offer unique habitat for many organisms, including endangered
species like sea otters. This diverse community attracts over 7 million visitors to Monterey
County every year.
Humans are adding extra carbon to the atmosphere in the form of carbon dioxide (CO2) by
burning fuels like wood, coal, oil, and gas. Increased CO2 in the atmosphere is one cause of
climate change. Changes to the climate patterns known as El Niño and La Niña patterns directly
impact the stability of kelp forests. Through the process of photosynthesis, kelp converts CO2 that
could otherwise become greenhouse gases in the atmosphere into oxygen (O2). Kelp stores the
carbon in its biomass. This process is called carbon sequestration.
A watershed is an ecosystem that contains a set of streams and rivers that all drain into a single
larger body of water. The body of water could be a wetland, lake, pond, and groundwater (water
stored underground). The watershed can also include cities, factories, mines, and farmland. Eleven
major watersheds drain into Monterey Bay, flowing through major cities and vast farmlands.
These human developments can affect the health of the watershed ecosystem and ultimately the
kelp forests in Monterey Bay.
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Courtesy of National Oceanic and Atmospheric
Administration
This map shows the Monterey Bay NMS and the
eleven watersheds that drain into the bay.
In the past 40 years, the kelp population has declined dramatically in the sanctuary. Some of the
main factors affecting the kelp population are kelp harvesting, mariculture (ocean farming),
decline in sea otters populations, and pollution runoff from agriculture (land farming).
Ecosystem Services
• Biological regulation: Sea otters are considered the keystone species of the kelp forest. Sea otters
keep urchin populations in check, which in turn protects kelp populations.
• Climate regulation: Kelp forests help regulate the global climate by converting atmospheric CO2
into O2 and storing the carbon in the kelp biomass.
• Food: Algin in kelp is an important additive ingredient in many food products.
• Habitat refuge: Kelp forests are a unique habitat for many organisms.
• Natural resource: Algin in kelp is an additive used in toothpastes, shampoos, soap, pills, dyes,
and paints.
• Nutrient cycling: Primary production in kelp forests is important for maintaining the carbon
cycle.
• Primary Production: Many ecosystem services are possible because of the high primary
productivity of kelp and phytoplankton.
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• Tourism: Over 7 million tourists visit Monterey County every year. Because of this massive
draw, there are over 22,000 full-time tourist-related jobs, generating over $2 billion of income
for the county each year!
ABIOTIC DATA
The temperate climate in the Monterey Bay is relatively mild with warm summers and cool
winters. A typical day during summer and early fall at Monterey Bay NMS is cool, with air
temperatures of 16 degrees Celsius (°C) to 18°C. Winds blow from the northwest at about 15 km
per hour. The skies may be somewhat cloudy, but rain rarely falls. This is the dry season at
Monterey Bay.
The wet season is between November and early April. Different amounts of rain fall at different
places in Monterey Bay. During the wet season, temperatures are cooler but not extremely cold,
usually about 10°C –13°C.
A mix of subarctic and tropical waters affects the water temperature and salinity at Monterey Bay.
Usually the salinity of the water (3.3 percent) is slightly less than the average ocean water salinity
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(3.5 percent). Streams flowing into the ocean can also affect salinity. The water is warmest in the
early fall, 15°C, and coolest in the late winter, 11°C.
Courtesy of NOAA Photo Library
Light levels are low on the ocean bottom in a kelp forest.
Light does not penetrate water easily. For this reason, the amount of light on the ocean's surface is
not the same amount that hits the ocean floor. The top few meters has a lot of light and is called
the photic zone. The amount of light decreases with depth. In some areas, light can penetrate as
deep as 90 meters (m). In a kelp forest, the light cannot go as deep because the kelp is so dense.
The area that does not have light is called the aphotic zone.
In addition to kelp forests, Monterey Bay NMS also includes sandy beaches, coastal dunes, rocky
intertidal areas, and deep ocean. These other habitats can have significant impacts on the kelp
forest ecosystem. For example, in the spring, water from deep canyons moves up to the surface.
This movement of water to the ocean surface is called upwelling. Upwelling brings cold,
nutrient-rich water up into the photic zone, resulting in high productivity by phytoplankton.
Upwelling is strongest in the spring.
Every 3 to 7 years, a climate pattern called El Niño disrupts the ocean-atmosphere system in the
Pacific Ocean. El Niño, which usually occurs in the winter, is caused by a change of current
patterns near the equator. Weaker equatorial winds do not draw up the colder, nutrient-rich
water from deep in the ocean. This allows the warmer, nutrient-poor surface water to flow in the
currents that feed Monterey Bay. Without strong upwelling, water is warmer and the kelp forest
is less productive.
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Courtesy of NOAA Photo Library
In January 1998, during the El Niño event, warm equatorial waters did not contain nutrients
needed by phytoplankton to grow and produce chlorophyll.
Courtesy of NOAA Photo Library
By July 1998, at the end of the El Niño event, colder equatorial water appeared. A bloom of
photosynthetic phytoplankton and chlorophyll indicated increased nutrients.
During an El Niño year, the water at Monterey Bay NMS and along the entire west coast of the
United States is unusually warm, which results in higher rainfall and more storms. The year
following an El Niño is usually a La Niña year. During La Niña, the water is cooler than normal
and more productive. El Niño and La Niña patterns directly impact the stability of kelp forests.
The ocean floor in Monterey Bay NMS is mostly hard granite. Within the sanctuary, the ocean
floor drops gradually at first. This shallow area is the continental shelf. As you move farther from
land, the ocean floor drops steeply onto the abyssal plain. The sanctuary also has underwater
canyons up to 4,000 m deep. Monterey Canyon is the deepest, and it runs right out from
Monterey Bay. Because these deep canyons are so close to shore, deep-ocean creatures can be
observed near the coast, making Monterey Bay a unique area for research.
Pollution refers to substances introduced by industry and other human activity that can harm an
ecosystem. There are two main types of pollution: point source pollution and nonpoint source
pollution. Point source pollution comes from an identifiable source like a pipe or factory
smokestack. Federal laws like the Clean Water Act have regulated many forms of point source
pollution. Nonpoint source pollution comes from many different sources that aren’t always
identifiable. Storm water runoff and accumulation of runoff from farms or lawns are examples of
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nonpoint source pollution. This form of pollution is much harder to control because there are so
many contributing sources. Monterey Bay NMS is most affected by nonpoint source pollution.
One kind of nonpoint source pollution is fertilizer. Land use of fertilizer can change the water.
Fertilizers are chemicals with nutrients that help plants grow. This may sound helpful, but when
too much fertilizer is sprayed on fields or lawns in nearby California, it runs off into streams and
rivers that eventually carry it to the ocean. These chemicals stimulate unusual growth of algae and
cyanobacteria, creating an excess of growth called algal blooms. These blooms can block sunlight
from the kelp forests and stop the kelp from growing. They also produce toxins (harmful
substances) that can threaten the health of humans and the kelp forest ecosystem.
Sediments (sand and silt) in runoff can also block sunlight in the ocean and reduce kelp growth.
All these sources of pollution are difficult to prevent because they come from many different
places. Humans over a large area are affecting the water quality of Monterey Bay.
BIOTIC DATA
In a kelp forest, the “trees” of this forest are actually species of brown algae commonly known as
kelp. Kelp forests are one of the most productive ecosystems on Earth. In addition to kelp,
phytoplankton, algae and zooxanthellae enrich the ecosystem.
Annual primary productivity is the amount of energy provided by the producers to the ecosystem
each year. In Monterey Bay, the annual primary productivity is dependent on the amount of
upwelling that year. During years of significant upwelling, the productivity of kelp forests is as
high as tropical rain forests and coral reefs.
During upwelling events, kelp forest primary productivity is as high as tropical rain forests
and coral reefs.
Like terrestrial forests, kelp forests have patterns of seasonal growth. In the spring, juvenile kelp
grow quickly. By summer, there is a lush canopy of kelp. In the fall, growth slows and the kelp
fronds become ragged and torn. In the winter, when the surf is rougher, older kelp can tear loose
from the ocean floor. Giant kelp grows very slowly in the winter.
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Kelp requires cold temperatures to reproduce sexually, which starts the cycle over each year.
During El Niño years, when the temperatures are higher than normal, the kelp may not be able
to reproduce. For giant kelp, this results in older and more fragile kelp throughout the kelp forest
the next year.
Courtesy of Monterey Bay NMS
Kelp continues to grow up to 0.6 m per day after reaching the water surface.
The fronds form a dense mat along the surface.
The kelp forest can be divided into layers that support different communities of organisms:
substrate, mid-water, and canopy.
The substrate layer is at the bottom, where the kelps
are attached to rocks with root-like structures called
holdfasts. Abalones, bat stars, brittle stars, and sea
urchins are a few of the animals found in the substrate
layer. Spiny lobsters and hermit crabs hide in the rocks
and scavenge for bits of detritus.
The mid-water layer is where the leaf-like fronds of
kelp are suspended in the water. Turban snails cruise
up and down the fronds in search of food. Fish such as
garibaldi, sheepheads, and giant kelpfish swim among
the fronds. Kelp crabs climb up and down the kelp
stipe, adding bits of kelp to their carapace for
camouflage.
The canopy layer is closest to the surface. Here, the
kelp blades bob on the surface waves. Colorful
nudibranchs slide across the kelp blades. Some kelp
fronds are covered with small encrusting bryozoans.
Zooplankton and phytoplankton float in the water near
the surface, moving with the current.
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The kelp forest supports different
communities at different depths in the water.
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Throughout the many layers, predators such as leopard sharks, red octopus, and sea otters hunt for
food.
One important ecological role is known as a keystone species. The term keystone comes from the
name of a stone used when constructing stone arches. This important stone holds the other stones
in place. Similarly, keystone species play an important role in maintaining a community of
organisms. Not all communities have keystone species, but for those that do, the loss of that one
species can destroy the whole ecosystem.
Sea otters are considered the keystone species of the kelp forest, and they have been hunted nearly
to extinction. Recent efforts to restore sea otter populations have had significant positive impacts
on the health of the ecosystem as a whole.
Southern sea otters have a broad diet of shellfish, sea urchins, crab, fish, and snails. Otters use
rocks, shells, and even discarded glass soda bottles as tools to help break open urchins and shellfish.
They have voracious appetites and may eat up to one-quarter of their weight each day.
Sea otters can limit the population of sea urchins, which is good for the kelp forest because sea
urchins eat so much kelp that they can create large areas where the kelp is entirely gone. These
areas are called urchin barrens. Researchers learned that the presence of sea otters is essential to
keeping urchin populations stable.
After steady growth, sea otter populations have been declining in recent years. Scientists are
working hard to find answers. Some factors that may be causing the sea otter decline include
boating activities by humans, fishing in the area, and pollution. About 40 percent of sea otters die
from disease, which could be caused by increased pollution. As a result of their protection under
the Endangered Species Act, the number of otter deaths directly related to human conflict are
decreasing, and regulation for harmful fishing nets have improved.
Courtesy of Monterey Bay NMS
Sea otters float atop the kelp forest at Cannery Row.
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