Download Chapter 16 - Marine Ecosystems

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Mangrove Swamps, Seagrasses
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Chapter 16 Pages 16-3 to 16-9
Ecology and Ecosystems
Ecology and Ecosystems
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The Science of Ecology
Chapter 16 Page 16-3
Ecology and Ecosystems
n With the rise of environmental awareness, the term
ecology has become a buzzword thrown about by
the media and politicians.
n You may already have a general idea of what ecology
is, but to discuss marine ecology clearly it’s important
to be precise and specific.
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Chapter 16 Page 16-3
Ecology and Ecosystems
The Science of Ecology
n Ecology is the science that studies how
organisms relate to each other and their
environment.
 Ecology embraces the broad range of disciplines,
including biology, physics, geology, climatology,
oceanography, paleontology, and even astronomy.
 Beyond biotic (living) factors, the study of ecology
considers the abiotic (nonliving) aspects of the
environment.
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Chapter 16 Page 16-3
Ecology and Ecosystems
The Science of Ecology
n Abiotic aspects include temperature, wind, pH,
currents, minerals, and sunlight.
n Ecology also examines the biological factors, such as
the quantity and type of organisms in an
environment.
n Ecology studies the relationships and interactions of
the abiotic and biotic aspects of the environment.
n The goal is to understand how, through relationships
and interactions, changes in an environment will
affect those organisms in the environment.
n In marine ecology, the four branches of
oceanography come together.
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Chapter 16 Pages 16-3 to 16-5
Ecology and Ecosystems
Ecology Terminology
n At some level you’re probably familiar with the
concept of an ecosystem.
 Definition: A distinct entity usually with clearly
defined physical boundaries, distinct abiotic
conditions, an energy source, and a community of
interacting organisms through which energy is
transferred.
 No ecosystem exists entirely in isolation (except
under artificial conditions). The ocean is
composed of interacting, complex ecosystems.
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Chapter 16 Pages 16-3 to 16-5
Ecology and Ecosystems
Ecology Terminology
n A community is a collection of different
organisms living and interacting in an ecosystem.
This includes all species and types of organisms.
n A population is a group of the same species living
and interacting within a community.
 The interaction is part of the definition because
sometimes two populations of the same species
live in a single community.
 Can you think of examples?
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Chapter 16 Pages 16-3 to 16-5
Ecology and Ecosystems
Ecology Terminology
n A habitat includes the area and
conditions in which you find an
organism.
 Some species are adapted to or occur
in very specific habitats, whereas
others range over a variety of habitats.
 Chitons, for example, live in the rocky
intertidal zone, whereas octopuses live
in a wide depth range and in many
different parts of a reef. The chiton has
a narrowly defined habitat compared to
the octopus.
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Ecology Terminology
Chapter 16 Pages 16-3 to 16-5
Ecology and Ecosystems
n A microhabitat exists on a very small scale. For
example, tiny crustaceans and worms live in the
spaces between sand grains on the sea floor.
 Organisms in this microhabitat are a type of
infauna called meiofauna.
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Chapter 16 Pages 16-3 to 16-5
Ecology and Ecosystems
Ecology Terminology
n An organism’s role in its habitat is called its
niche.
 Very different species can occupy the same niche.
On coral reefs, for example, cleaner-shrimp and
cleaner-fish both survive by feeding on the
parasites and dead or injured skin of reef fish.
 To avoid confusing habitat and niche, think of the
habitat is an
organism’s address,
and the niche
as it’s job.
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Chapter 16 Pages 16-6 to 16-8
Ecology and Ecosystems
Energy Flow and Nutrient Cycles
n Trophic relationships and nutrient cycles are concepts
fundamental to ecology.
 They describe how energy and matter form the basis for
interaction among organisms and between organisms and
the environment.
n Recall that photosynthesizers and chemosynthesizers bring
energy from the sun and chemicals into the food web.
 This energy transfers up through the food web, but most of
the energy gets lost as heat in the process.
 Only about 10% of the available energy passes from one
trophic level to the next.
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Energy flow.
This illustration shows
how energy flows
through a functioning
ecosystem.
Chapter 16 Pages 16-6 to 16-8
Ecology and Ecosystems
Energy Flow and Nutrient Cycles
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Chapter 16 Pages 16-6 to 16-8
Ecology and Ecosystems
Energy Flow and Nutrient Cycles
n The energy flow through the food web affects an ecosystem by
determining how much energy is available for organisms at
higher trophic levels.
 In all ecosystems, there are fewer high-level predators than
low-level prey.
 The amount of primary production shapes the ecosystem.
 High primary production creates the potential for more
organisms at high trophic levels, and the potential for more
trophic levels.
 Anything that affects energy flow will also affect the
ecosystem.
 Even with ample primary production the ecosystem would
lose many of the high-level organisms in its community.
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Interrupted energy flow.
A substantial decline in
an ecosystem’s primary
consumers disrupts energy
flow to higher trophic levels.
Here we see a reduction
of the amount and types
of prey available to killer
whales. The whale
population will suffer in
this ecosystem unless
they move on to an area
with more productivity, or
more primary consumers
to transfer energy to
higher trophic levels.
Chapter 16 Pages 16-6 to 16-8
Ecology and Ecosystems
Energy Flow and Nutrient Cycles
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Energy Flow and Nutrient Cycles
Chapter 16 Pages 16-6 to 16-8
Ecology and Ecosystems
n Energy flows through an ecosystem, eventually being
lost as heat into the water, atmosphere, and space.
 Nutrients, on the other hand, aren’t lost.
 Carbon, nitrogen, phosphorus, and other
crucial elements cycle through the Earth’s
ecosystems.
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Chapter 16 Pages 16-6 to 16-8
Ecology and Ecosystems
Energy Flow and Nutrient Cycles
n The nitrogen nutrient cycle is thought to be more limited in
marine ecosystems than in terrestrial ecosystems.
 Because: Inorganic nitrogen must be fixed into organic
compounds before it can be used by organisms.
 Nitrogen-fixing bacteria that do this live primarily in terrestrial
ecosystems.
 Seabird droppings, erosion, and runoff carry organic nitrogen
compounds (and phosphorus) from terrestrial environments
into the marine environment.
 This is an example of how ecosystems don’t exist entirely in
isolation.
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Energy Flow and Nutrient Cycles
Chapter 16 Pages 16-6 to 16-8
Ecology and Ecosystems
Nitrogen Cycling
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Chapter 16 Pages 16-6 to 16-8
Ecology and Ecosystems
Energy Flow and Nutrient Cycles
n The ecological significance of nutrient cycles is usually greater
than that of energy flow.
 Why? Nutrients are usually a limiting factor, whereas energy
is usually not. Compare many warm, tropical marine
ecosystems with cold, temperate marine ecosystems.
 Tropical ecosystems generally have more energy (sunlight)
available, yet oceanic conditions don’t supply as many
nutrients to tropical regions.
 One of the few highly productive marine ecosystems
found in tropical waters is the coral reef.
 Temperate coastal waters, by comparison, have less
overall sunlight, but receive far more nutrients. For this
reason, the most highly productive marine ecosystems are
found in colder water.
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Chapter 16 Pages 16-10 to 16-14
Ecosystems in the Open Sea
Ecosystems in the Open Sea
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Chapter 16 Pages 16-10 to 16-12
Ecosystems in the Open Sea
Euphotic Zone Ecosystems
n The euphotic zone comprises only 1% of the ocean,
yet the majority of marine life lives there.
 Extends as deep as 200 meters (656 feet), but in
coastal waters with more turbidity, light may only
penetrate to about 30 meters (100 feet).
 The euphotic zone is where photosynthetic
organisms live, and light energy transfers
through food webs as chemical energy.
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n The neuston are the plankton that live in the
uppermost layer of the ocean.
 This ecosystem is very thin – only a few
millimeters in many instances.
 It receives the maximum sunlight and because it
covers about 71% of the Earth’s surface.
Chapter 16 Pages 16-10 to 16-12
Ecosystems in the Open Sea
Euphotic Zone Ecosystems
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Chapter 16 Pages 16-10 to 16-12
Ecosystems in the Open Sea
Euphotic Zone Ecosystems
n There have been surprisingly few studies to compare the
neuston layers to the water layers below.
 It is known that the first few millimeters to a few centimeters
of water differ substantially from the water below.
 Generally, neuston layers hold significantly more
nutrients, chlorophyll a, and carbon compounds.
 Surface tension supports eggs, larvae, and microscopic life
on the top film of the water.
 Cyanophyte, diatom, and dinoflagellate populations in the
neuston ecosystem may be 10,000 times more numerous
than in the water just a few millimeters deeper.
 This makes the neuston zone an important ecosystem for
worldwide primary productivity.
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Chapter 16 Pages 16-10 to 16-12
Ecosystems in the Open Sea
Euphotic Zone Ecosystems
n This isn’t true globally, however. In some places,
photosynthesis and primary productivity are higher
below the neuston ecosystem.
 One reason may be photoinhibition.
Photoinhibition seems to be prevalent in tropical
seas.
 Because there’s little water to protect neuston
organisms, ultraviolet light may account for some
of the photoinhibition.
 If this is true, ozone depletion may make
photoinhibition worse as even more UV light
makes it to the Earth’s surface.
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Chapter 16 Pages 16-10 to 16-12
Ecosystems in the Open Sea
Euphotic Zone Ecosystems
n An important factor reducing primary productivity in the
neuston ecosystem may be pollutants.
 A variety of pollutants from the atmosphere and runoff enter
the euphotic zone.
 How pollutants affect the neuston ecosystems concerns
scientists with respect to global climate change.
 The ocean plays an important role in moderating global
climate - particularly removing CO2.
 Many oil-based chemicals, float on water, creating a barrier
that slows or stops carbon dioxide (and other gases) from
dissolving into the water below. By affecting the euphotic
zone ecosystems, these pollutants may contribute to global
climate change.
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Chapter 16 Pages 16-10 to 16-12
Ecosystems in the Open Sea
Euphotic Zone Ecosystems
n Floating debris, whether natural or human-produced,
acts as potential shelter and attracts marine life.
 This creates distinct neustonic ecosystems that
thrive around floating material in the water.
 The world’s largest floating ecosystem is the
Sargasso Sea - a complex community.
 Sargassum mat organisms include tiny fish of
many species, crustaceans, and other organisms.
 On the other hand, the Sargassum fish is a
species of frogfish adapted specifically to this
ecosystem. It blends in with the Sargassum,
preying on small crustaceans and fish.
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Chapter 16 Pages 16-10 to 16-12
Ecosystems in the Open Sea
Euphotic Zone Ecosystems
n The Sargasso Sea and other euphotic
zone ecosystems found around floating
debris provide another example of how
ecosystems interact.
 Predatory fish hide under Sargassum
or debris, feeding on fish and other
neustonic organisms that live there.
 These predators in turn provide food
for pelagic fish, sharks, dolphins, and
other large predators.
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Chapter 16 Pages 16-12 to 16-14
Ecosystems in the Open Sea
Continental Shelf Ecosystems
n The neritic zone consists of the water between the low-tide mark
and the edge of the continental shelf.
 This zone can range from only a few to several hundred
kilometers or miles wide.
n The neritic zone is a significant marine ecosystem because
it is the most productive region in the ocean.
 The area tends to keep nutrients in the shallow, photic zone
and helps retain heat from the sun.
 Being near the shoreline - the neritic zone benefits from
nutrients in river runoff also.
 Nutrients rising with currents from deep water at the shelf
edges also make this zone biologically rich.
 All of these factors combine to make the neritic zone a highly
productive ecosystem.
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Chapter 16 Pages 16-12 to 16-14
Ecosystems in the Open Sea
Continental Shelf Ecosystems
Neritic Zone Productivity
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Chapter 16 Pages 16-12 to 16-14
Ecosystems in the Open Sea
Continental Shelf Ecosystems
n Upwelling plays a significant role in the balance
of coastal ocean ecosystems.
 This is because upwelling brings nutrients from
deeper water to shallow, more productive depths.
 This is especially significant with respect to fecal
pellets and other nutrients that sink to the
relatively less productive bottom in the abyssal
zone.
 Wind causes upwelling that returns nutrients to the
upper ocean depths.
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Chapter 16 Pages 16-12 to 16-14
Ecosystems in the Open Sea
Continental Shelf Ecosystems
n The role of upwelling is unmistakable.
 Areas with the highest upwelling activity also have
the highest nutrient levels.
 These correspond with many of the ocean’s
highest productivity regions.
 Examples include the waters offshore of Peru, the
Bering Sea, the Grand Banks in the Atlantic, and
the deep water surrounding Antarctica.
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Chapter 16 Pages 16-12 to 16-14
Ecosystems in the Open Sea
Continental Shelf Ecosystems
Areas of Coastal Upwelling
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Chapter 16 Pages 16-15 to 16-22
Coastal Ecosystems - Part 1
Coastal Ecosystems Estuaries, Salt Marshes,
Mangrove Swamps, Seagrasses
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Chapter 16 Pages 16-15
Coastal Ecosystems - Part 1
High Productivity Marine Environments
n Coastal ecosystems are generally highly
productive ecosystems for several reasons.
 They benefit from nutrient-rich runoff from land.
Because they’re shallow, the benthic organisms in
these ecosystems live in the upper photic zone,
instead of the bottom as in the open sea.
 Salt-tolerant plants can grow in the well-lit
shallows, providing shelter. These plants act as
the foundation for several different types of
ecosystems that cannot exist in the open ocean.
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n The combination of nutrients, ample light, and shelter
make coastal ecosystems diverse and rich.
n While you don’t commonly find large organisms here
(though there are some), these ecosystems provide a
haven for juveniles of open ocean species.
n Mangrove swamps contribute to the health of coral
reefs in this way.
Chapter 16 Pages 16-15
Coastal Ecosystems - Part 1
High Productivity Marine Environments
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Chapter 16 Pages 16-15
Coastal Ecosystems - Part 1
High Productivity Marine Environments
n Human activities have wide-ranging potential
effects on coastal ecosystems.
 The effects are varied and immediately at hand.
 People have always tended to live near water,
putting humans in proximity with these
ecosystems - this causes problems.
 Agriculture, for example, can alter these
ecosystems when excess fertilizer washes
seaward with rain runoff. Can you name more?
 The variety of human activities is so wide we can’t
always anticipate all the consequences to
ecosystems.
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n Because the effects are immediately at hand, coastal
ecosystems may experience the consequences more
severely.
 Pollutants, for example, often reach coastal
ecosystems in concentrated form.
 Open ocean ecosystems, by contrast, benefit from
a diluting effect.
Chapter 16 Pages 16-15
Coastal Ecosystems - Part 1
High Productivity Marine Environments
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Chapter 16 Pages 16-15
Coastal Ecosystems - Part 1
High Productivity Marine Environments
n One particular concern with coastal ecosystems is
eutrophication, which is an overabundance of nutrients that
causes an ecological imbalance.
n Eutrophication is a stimulus to some species and a detriment to
others.
n Fertilizer runoff can dump excess nutrients in the water,
stimulating excessive algae growth or algae blooms. When the
algae die, degradation of biomass consumes available oxygen.
n The depletion of oxygen kills fish and other sea life.
n Although there are other causes of harmful algae blooms
(HABs), eutrophication is the most conspicuous.
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Chapter 16 Pages 16-16 to 16-17
Coastal Ecosystems - Part 1
Estuaries
n Estuaries exist where the tides meet rivers.
 They’re not found where all rivers enter the sea,
but they’re common where the tidal range is high.
 This allows high tide to push well up river, often
flooding large land areas.
 Estuaries may be large, complex deltas with
multiple inlets, lagoons, and islets or they may be
simple wide stretches of river entering the sea.
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Chapter 16 Pages 16-16 to 16-17
Coastal Ecosystems - Part 1
Estuaries
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Chapter 16 Pages 16-16 to 16-17
Coastal Ecosystems - Part 1
Estuaries
n Estuaries tend to trap and accumulate runoff
sediments, so they’re rich with nutrients and
biologically productive.
 Most of the major North American rivers flowing
into the Atlantic flow first into estuaries.
 This is why the North Atlantic doesn’t have as
much sediment flowing in to it as other ocean
basins have with comparable rivers.
 Estuaries trap much of the sediment. This also
makes estuaries sensitive to eutrophication
because the same process traps excess nutrients
such as fertilizer runoff.
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Chapter 16 Pages 16-16 to 16-17
Coastal Ecosystems - Part 1
Estuaries
n Estuaries act as a dumping ground, filter, and
absorber of nutrients (and pollutants).
 Estuaries are the kidneys of the biosphere
because of their cleansing function.
 The continuous replenishment of nutrients results
in ecosystems with high primary productivity from
algae and halophytes - saltwater plants. These, in
turn, support a large community of primary and
secondary consumers.
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Chapter 16 Pages 16-16 to 16-17
Coastal Ecosystems - Part 1
Estuaries
n Some factors limit productivity in estuaries.
 One is that organisms in this ecosystem must
tolerate wide salinity ranges.
 The osmotic stress caused by the rising and falling
tides mixing with fresh water proves fatal to many
organisms.
 Organisms that tolerate wide salinity ranges are
called euryhaline organisms. Therefore,
variations in salinity tend to reduce the variety of
species.
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Chapter 16 Pages 16-16 to 16-17
Coastal Ecosystems - Part 1
Estuaries
n Another productivity limit results from the tendency of
decomposition to deplete the oxygen in the nutrientrich sediments.
 This limits the benthic organisms that can thrive in
estuaries.
 The rotten eggs smell common to these areas
comes from sulfides released by thriving
anaerobic sulfur bacteria.
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Chapter 16 Pages 16-16 to 16-17
Coastal Ecosystems - Part 1
Estuaries
n Estuaries provide a region of shallow, sheltered water
and nutrients, making them excellent nurseries.
 By providing a rich haven, larvae and juveniles of
open ocean species can elude predation and grow
before venturing out to sea.
 Estimates show that estuary ecosystems serve
as nurseries for more than 75% of commercial
fish species.
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Chapter 16 Pages 16-16 to 16-17
Coastal Ecosystems - Part 1
Estuaries
n Estuaries contribute to the productivity of
adjacent marine ecosystems in at least two ways.
 First, surviving juveniles migrate from the
estuaries as they grow and mature. They increase
the number of individuals that survive the
hazardous larval and juvenile stages.
 Second, estuaries provide a steady stream of
nutrients to adjacent marine ecosystems, while
trapping sediment and other materials in runoff
from rain and storms.
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Chapter 16 Pages 16-17 to 16-19
Coastal Ecosystems - Part 1
Salt Marshes
n Salt marshes exist in estuaries and along the coasts.
n They are found where flat, gently sloping shore are
washed by the tides with nutrient-rich sediments.
n Rivers provide a source of sediments and nutrition.
n Conditions within a salt marsh vary, which affects
the types of organisms inhabiting different areas
within the ecosystem.
n The upper marsh includes the areas only rarely
flooded by the tides.
n The lower marsh includes areas flooded by salt water
as a regular part of the tidal cycle.
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Salt Marsh
Plant
Community
Chapter 16 Pages 16-17 to 16-19
Coastal Ecosystems - Part 1
Salt Marshes
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Chapter 16 Pages 16-17 to 16-19
Coastal Ecosystems - Part 1
Salt Marshes
n Most plants can’t live in seawater because osmosis
dehydrates them.
 Halophytes, on the other hand, have adaptations
that allow them to survive in salt water.
 Thanks to these adaptations, halophytes
occupy a niche with little competition from
other plants, and become the dominant
species.
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Chapter 16 Pages 16-17 to 16-19
Coastal Ecosystems - Part 1
Salt Marshes
n Halophytes in the lower marsh deal with constant
osmotic stress.
 The hollow reed Spartina sp., called cordgrass, is
a good example of halophyte adaptation to this
part of the ecosystem.
 Spartina sp. excludes salt from its tissues and
moves oxygen it produces by photosynthesis to its
roots.
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n Plants in the upper marsh don’t have to deal with
daily tides.
n In addition, the inflow of fresh water dilutes salt water,
reducing osmotic stress.
n Organisms thriving in this part of the ecosystem
adapt differently. One example is Salicornia sp., or
pickleweed.
Chapter 16 Pages 16-17 to 16-19
Coastal Ecosystems - Part 1
Salt Marshes
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Salt Marshes
Chapter 16 Pages 16-17 to 16-19
Coastal Ecosystems - Part 1
n Pickleweed handles excess salt by storing it in
sacrificial leaves.
n When the salt load accumulates to a certain point,
the leaf drops away, taking the salt with it.
n Salicornia grows another leaf to take its place.
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Chapter 16 Pages 16-17 to 16-19
Coastal Ecosystems - Part 1
Salt Marshes
n Halophytes dominate the salt marsh, yet they are not
food for many organisms.
 Salt marsh plants are tough and salty, making
them unsuitable for most herbivores.
 Their root systems hold sediment, which, along
with the accumulation of dead halophytes, creates
dense mats of detritus.
 In the salt marsh, detrital mats provide habitats
for huge communities of invertebrates, water
birds, juvenile fish, larva, eggs, and other
organisms.
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Chapter 16 Pages 16-17 to 16-19
Coastal Ecosystems - Part 1
Salt Marshes
Food Web
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Chapter 16 Pages 16-19 to 16-21
Coastal Ecosystems - Part 1
Mangrove Swamps
n Mangrove swamps include many species.
n They all play an important role in the marine
environment, especially coral reefs.
n In many respects, mangroves occupy similar niches
as the halophytes that characterize salt marshes, but
they’re bigger, tougher, and found in tropical climates.
n Mangrove species have various
adaptations that allow them to
live in salt water and anaerobic mud.
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Chapter 16 Pages 16-19 to 16-21
Coastal Ecosystems - Part 1
Mangrove Swamps
n Red mangroves grow above the waterline on stilt-like
roots. This allows oxygen to reach the roots. a. They
obtain fresh water by filtering seawater through its
adapted roots, which exclude the salt.
n This is an example of reverse osmosis, which is the
process of transporting water through a
semipermeable membrane against the natural
osmotic pressure gradient.
n This is a form of active transport, which is the
process of a cell moving materials from areas of low
concentration to areas of high concentration.
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Chapter 16 Pages 16-19 to 16-21
Coastal Ecosystems - Part 1
Mangrove Swamps
n Black Mangroves have roots that grow in the
sediment below the waterline.
 These mangroves aerate their roots with snorkellike tubes called pneumatophores, which carry
air from above the surface to the roots.
 Some black mangroves eliminate salt through
sacrificial leaves, like the pickleweed. Others have
special salt glands in their leaves.
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Mangrove Swamps
Chapter 16 Pages 16-19 to 16-21
Coastal Ecosystems - Part 1
n White mangroves lack such specialized adaptations.
n They’re very saltwater tolerant, but thrive high on the
tideline where they don’t need special root
adaptations. These mangroves receive sufficient
freshwater runoff to survive.
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Chapter 16 Pages 16-19 to 16-21
Coastal Ecosystems - Part 1
Mangrove Swamps
n Regardless of species or adaptations, mangroves share two
important characteristics that make them the basis of mangrove
ecosystems.
 They have strong, tangled roots that provide habitats for
juvenile fish and invertebrates - they are nurseries for nearby
marine ecosystems, particularly coral reefs.
 They hold the soil well, protecting the habitat and coast from
erosion due to storm surges, waves, and weather.
n Without strong mangrove root systems, tropical storms would
quickly wash away many tropical islands and beaches.
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Chapter 16 Pages 16-19 to 16-21
Coastal Ecosystems - Part 1
Mangrove Swamps
n Mangroves trap nutrients, much as estuaries do,
helping to protect coral reefs and other nearby
marine ecosystems.
 However, because they’re swampy, sulfidesmelling mosquito havens, until relatively recently
people viewed them as wastelands.
 Today we know they’re
ecosystems crucial to the
global ecosystem, but
mangroves continue to vanish.
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Seagrasses
Chapter 16 Pages 16-21 to 16-22
Coastal Ecosystems - Part 1
n Seagrass ecosystems are similar to other halophytebased ecosystems in that they stabilize sediments
and provide shelter and habitats for other organisms.
 However, seagrasses differ from other
halophytes in several important ways that
make them and their ecosystems distinct.
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Chapter 16 Pages 16-21 to 16-22
Coastal Ecosystems - Part 1
Seagrasses
n Seagrasses are rooted, vascular flowering plants that live
entirely under water except during rare, very low tides.
 Some species live as deep as 30 meters (100 feet).
 Seagrasses can grow as members of a mangrove or salt
marsh ecosystem.
 Commonly seagrass grow spread across the bottom like
underwater pastures - they mat the sediment below.
 Seagrasses extract oxygen from the water and have internal
air canals.
 Most species even release pollen into the current to
reproduce, much like terrestrial plants.
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Seagrasses
Chapter 16 Pages 16-21 to 16-22
Coastal Ecosystems - Part 1
n Unlike most halophytes, seagrasses are edible
and provide food for ecosystem inhabitants.
n They are heavily grazed by microbes,
invertebrates, fish, turtles, and even manatees
and dugongs.
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Chapter 16 Pages 16-23 to 16-29
Coastal Ecosystems - Part 2
Coastal Ecosystems Intertidal Zones, Beaches,
Kelp and Seaweed, Coral Reefs
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Chapter 16 Pages 16-23 to 16-24
Coastal Ecosystems - Part 2
Intertidal Zones
n When we think of coastal ecosystems, we tend to
think of mangroves, estuaries, and similar
ecosystems.
 The numerous complex organisms make their
productivity conspicuous. However, in every place
the ocean touches land, you’ll find a coastal
ecosystem with rich communities.
n Ecosystems in the world’s intertidal zones exist in
areas that may be above the waterline at times.
n Other portions of intertidal zones reach depths of
about 10 meters (33 feet).
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Chapter 16 Pages 16-23 to 16-24
Coastal Ecosystems - Part 2
Intertidal Zones
n The supralittoral zone is the area
only submerged during the highest
tides.
 The greatest challenges facing
organisms that live in
supralittoral ecosystems are
drying and thermal stress.
 A constant spray of seawater that
evaporates also results in high
salt levels.
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Chapter 16 Pages 16-23 to 16-24
Coastal Ecosystems - Part 2
Intertidal Zones
n Organisms with habitats in the supralittoral zone have
adaptations that help them retain moisture.
 Unlike many marine organisms, they can either
obtain oxygen from the air or store sufficient
oxygen in their tissues to endure many hours out
of the water.
 They are hardy enough to withstand periodic
motion and pounding by waves.
 Barnacles, periwinkles, and limpets are examples
of organisms adapted to life in the supralitttoral
zone.
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Chapter 16 Pages 16-23 to 16-24
Coastal Ecosystems - Part 2
Intertidal Zones
n The rest of the littoral zone (the area between high
and low tide) faces similar challenges. Life here isn’t
left above the surface for extended periods like the
supralittoral zone.
 These organisms also face the challenges of
drying out, thermal stress, and water motion.
 Progressing seaward, the environment becomes
less stressful with respect to drying out and
thermal stress, though waves and surge remain
challenges.
 Organisms that thrive here are seaweeds, starfish
anemones, and mussels.
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n The lowest part of the littoral zone is rarely exposed
to air - only at extremely low tides.
 With ample water, nutrients, and sunlight, this is a
highly productive region in most coastal
ecosystems.
 One challenge to life here, therefore, is intense
competition.
Chapter 16 Pages 16-23 to 16-24
Coastal Ecosystems - Part 2
Intertidal Zones
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Rocky
Shore
Community
Chapter 16 Pages 16-23 to 16-24
Coastal Ecosystems - Part 2
Intertidal Zones
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Chapter 16 Pages 16-24 to 16-25
Coastal Ecosystems - Part 2
Beaches
n To the untrained eye, the typical sandy beach
appears nearly devoid of life.
 It looks almost like a desert, with only an
occasional shell or starfish.
 The reality is that beaches are rich and productive
ecosystems.
 They also have important roles that affect other
marine ecosystems.
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n Sand results from the energy of waves weathering
the coast and washing it into the sea with river runoff.
 Scientists think that the sands on the world’s
beaches may have migrated thousands of years
before washing ashore.
 In addition to minerals, living and dead organic
material accumulates into the sand mix.
Chapter 16 Pages 16-24 to 16-25
Coastal Ecosystems - Part 2
Beaches
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Chapter 16 Pages 16-24 to 16-25
Coastal Ecosystems - Part 2
Beaches
n Sand protects the coastline.
n As a wave comes ashore, it picks up sand. Each
sand grain dissipates a miniscule portion of wave
energy.
 That portion times billions and billions of sand
grains reduces the forces that wear away the
coastline.
 This is the first way that beaches affect
ecosystems. They reduce sedimentation caused
by coastal erosion.
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Chapter 16 Pages 16-24 to 16-25
Coastal Ecosystems - Part 2
Beaches
n Beach ecosystems are rich in organisms living on the
organic material in the sand mix.
 Complex organisms, including worms, mollusks,
and fish live in the submerged beach sand.
 Called meiofauna - benthic organisms that live in
the spaces between sand grains are very diverse.
 About a third of all known animal phyla have
representatives in the meiofauna.
 Additionally, algae and other
non-animal organisms live
among the sand grains.
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Chapter 16 Pages 16-24 to 16-25
Coastal Ecosystems - Part 2
Beaches
n The interaction between water motion and the
meiofauna provides the second way that beaches
affect other marine ecosystems.
 The physical and organic processes in the beach
ecosystem break down organic and inorganic
materials.
 This makes the beach a giant filter that processes
compounds from runoff to the sea or washed up
from the sea.
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n Seaweed refers to a diverse group of red, green, and
brown algae.
n All provide the bases for ecosystems among their
stipes, holdfasts, and blades.
n Among these, kelp ecosystems are probably the
most diverse.
Chapter 16 Pages 16-26 to 16-27
Coastal Ecosystems - Part 2
Kelp and Seaweed Ecosystems
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Chapter 16 Pages 16-26 to 16-27
Coastal Ecosystems - Part 2
Kelp and Seaweed Ecosystems
n You find kelp forests globally in cool water. This is because they
require the nutrients found in a cool ocean.
 The richest and most productive kelp ecosystems exist in
coastal waters with upwellings.
 In clear water with ample sunlight and nutrients, giant kelp
can reach 60 meters (196.8 feet) long that cover many acres
underwater.
 Kelp forests and other seaweed-based ecosystems are
among the most biologically productive ecosystems.
 Their primary production exceeds the primary productivity of
terrestrial forests and is almost equal to the productivity of
coral reefs.
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n Because of its dependence on sunlight, cool water,
and nutrients, kelp responds noticeably to
environmental changes.
n During ENSO events, for example, the coastal water
temperatures in Southern California rise. This often
causes massive die offs of kelp, disrupting the local
ecosystems for a year or more.
Chapter 16 Pages 16-26 to 16-27
Coastal Ecosystems - Part 2
Kelp and Seaweed Ecosystems
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n Kelp provides a clear example of why it’s important to
study ecology, not simply individual organisms.
 Until protected, in some areas the sea otter
was hunted nearly to extinction.
 Amazingly, in these areas the kelp began to die
off rapidly.
Chapter 16 Pages 16-26 to 16-27
Coastal Ecosystems - Part 2
Kelp and Seaweed Ecosystems
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Chapter 16 Pages 16-26 to 16-27
Coastal Ecosystems - Part 2
Kelp and Seaweed Ecosystems
n It turns out that while few organisms eat kelp, one
that does is the sea urchin.
 These echinoderms graze on the rubbery
holdfasts that anchor the kelp.
 Sea urchins are also one of the sea otter’s primary
foods.
 The energy required by a mammal living in cool
seawater is considerable, so the
average sea otter eats a
substantial number of sea urchins.
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Chapter 16 Pages 16-26 to 16-27
Coastal Ecosystems - Part 2
Kelp and Seaweed Ecosystems
n Killing the sea otters disrupted the kelp forest’s ecological
balance by removing the sea urchin’s chief predator.
 This allowed the sea urchin population to rise relatively
unchecked.
 More sea urchins meant more grazing on kelp holdfasts.
 In the end, the sea urchins ate the kelp faster than it could
grow.
 This is an excellent example of the interdependence that
exists within an ecosystem. It shows that each organism
contributes to a balance that allows life to thrive there.
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Chapter 16 Pages 16-27 to 16-29
Coastal Ecosystems - Part 2
Coral Reefs
n Of all the Earth’s ecosystems, few compare to the coral reef.
 Most scientists believe they are the most taxonomically
diverse ecosystems in the ocean.
 The Indo-West Pacific area between Papua New Guinea
and the Sulu and Celebes Seas has the world’s highest
marine species diversity.
 More than 2,000 species of fish are known, with new species
discovered every year.
 Scientists think corals and coral reefs originated here
because the further you go from this area, the less diversity
you find.
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Chapter 16 Pages 16-27 to 16-29
Coastal Ecosystems - Part 2
Coral Reefs
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Chapter 16 Pages 16-27 to 16-29
Coastal Ecosystems - Part 2
Coral Reefs
n While supporting immense diversity, coral reef ecosystems are
also fragile.
 For decades now, scientists, divers, and others familiar with
coral have been worried about their health.
 The conditions coral requires for life are narrow and specific.
It lives in clear water so that dinoflagellates (zooxanthellae)
coexisting in the polyps have light for photosynthesis.
 It also needs water that’s in moderate motion to prevent
sediments from accumulating on the polyps. Particulate
matter can clog and smother the polyps. It also reduces
the light reaching the algae inside.
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Chapter 16 Pages 16-27 to 16-29
Coastal Ecosystems - Part 2
Coral Reefs
n Coral ecosystems also require water that’s relatively
free of nutrients.
 This may seem odd considering the high
productivity of this ecosystem.
 However, coral ecosystems efficiently pass on and
preserve organic material.
 The lack of nutrients in the water actually protects
coral from competitive organisms.
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Chapter 16 Pages 16-27 to 16-29
Coastal Ecosystems - Part 2
Coral Reefs
n This is why eutrophication is one of the biggest
threats to coral ecosystems.
 A rise in water nutrient levels allows competitive
algae to overgrow and smother coral colonies.
 It also allows plankton to grow, reducing water
clarity and the amount of sunlight reaching the
polyps.
 To some extent, these are natural processes,
but over the last several decades
eutrophication levels have been rising.
Correspondingly, many reefs once dominated by
corals now have algae overgrowing them.
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Chapter 16 Pages 16-27 to 16-29
Coastal Ecosystems - Part 2
Coral Reefs
n Besides eutrophication, thermal stress threatens coral reef
ecosystems.
 A concern is that global warming may raise temperatures
above coral’s survival threshold.
 Another threat comes from sedimentation resulting from
coastal dredging and construction. This causes sediment to
accumulate on the polyps more quickly than water motion
can remove it.
 Coral diseases seem to be more common. These are
“attacks” by fungi, cyanophytes, bacteria, and other
competitive algae damaging and displacing corals.
 Scientists are still determining the likely sources and causes
for many of these.
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n Regardless of the specific threat, it’s important to
apply the principles of ecology to the overall picture.
 The concern isn’t for the coral alone, but the entire
coral ecosystem.
 Just as the loss of sea otters threatens kelp, the
loss of the corals threatens other organisms in the
ecosystem.
Chapter 16 Pages 16-27 to 16-29
Coastal Ecosystems - Part 2
Coral Reefs
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Chapter 16 Pages 16-27 to 16-29
Coastal Ecosystems - Part 2
Coral Reefs
n Parrotfish, for example, feed on coral. If the coral dies, the
parrotfish will dwindle as they lose their primary food source.
 Predators that feed on the parrotfish may similarly suffer.
Other organisms will not survive because the competitive
algae don’t provide the same habitat as a coral reef.
 The decline of coral is likely to have a domino effect
throughout not just the coral ecosystem but the entire marine
ecosystem.
 Ultimately, that means the loss of coral will affect the global
ecosystem in ways that ecologists are still trying to predict.
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Chapter 16 Pages 16-30 to 16-32
Polar Ecosystems
Polar Ecosystems
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Chapter 16 Pages 16-30 to 16-31
Polar Ecosystems
The Arctic
n The Arctic Ocean is bordered by the shallow
continental shelves of North America, Greenland,
Eurasia and Russia. It connects to the rest of the
ocean at the Bering Straight and the upper North
Atlantic.
 The Arctic is a deep basin and
much of this sea is a permanently
frozen ice cap.
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Chapter 16 Pages 16-30 to 16-31
Polar Ecosystems
The Arctic
n Marine ecosystems in the Arctic face the
challenges of reduced sunlight under the ice and
water that’s barely above freezing.
 For these reasons, divesity of organisms is limited
under the permanent ice cap.
 Species that do live in these conditions have
special adaptations. These include antifreezing
compounds in their blood and extremely low
metabolisms.
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Chapter 16 Pages 16-30 to 16-31
Polar Ecosystems
The Arctic
n At the edge of the ice cap, however, life
intensifies especially between March and
September.
 As the sun melts ice in the spring, water flows off
the ice, sinking into deep water.
 Warm currents from the south interact with the
cold water at the continental shelf edges.
 This process churns up nutrients from the shelf
bottom.
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The Arctic
Chapter 16 Pages 16-30 to 16-31
Polar Ecosystems
n Extremely high productivity occurs along an arc in the
North Pacific and across the North Atlantic from April
to August.
 These waters support massive fisheries, marine
mammals, and other organisms.
 This ecosystem flourishes from the nutrients
churned up from the bottom.
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Chapter 16 Pages 16-31 to 16-32
Polar Ecosystems
The Antarctic
n Antarctica has a more
extreme climate than the
Arctic.
n Also, the Antarctic differs
geographically from the
Arctic. Antarctica, is a
continent, not a frozen
sea.
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Chapter 16 Pages 16-31 to 16-32
Polar Ecosystems
The Antarctic
n It’s also not enclosed by the
continental shelves of other
continents. Instead, it has its own
continental shelf.
n The deepest and broadest ocean
ring surrounds the Antarctic. For
these reasons, the Antarctic
ecosystem has differences and
similarities compared to the Arctic.
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Chapter 16 Pages 16-31 to 16-32
Polar Ecosystems
The Antarctic
n During the winter, sea ice surrounding Antarctica freezes,
adding an area about the size of North America.
 When summer comes, the melting of this sheet sets off an
explosion of bioproductivity.
n As the temperature of the seawater drops, water molecules join
together to form sea ice. When the ice forms, the salts become
concentrated in the remaining seawater.
n This very cold, very salty, very dense water flows down the
continental margins of Antarctica and becomes Antarctic Bottom
Water, the most dense water in the ocean.
n Winds blowing along the coast result in Ekman Transport, which
moves water away from the continent at the surface, causing
upwelling in the area.
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Chapter 16 Pages 16-31 to 16-32
Polar Ecosystems
The Antarctic
n This nutrient-rich deep water reaches the surface at the
Antarctic Divergence, an area located at approximately 65˚ to
70˚ south latitude.
 This is the largest nutrient-rich area on Earth.
 The Antarctic Divergence supports massive phytoplankton
blooms from November through the southern summer.
 The copepod and krill populations are larger than any other
species population found in any other ecosystem.
 Single krill swarms have been estimated as exceeding 100
million tons, which is more than the world’s annual
commercial fish catch.
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Chapter 16 Pages 16-31 to 16-32
Polar Ecosystems
The Antarctic
n The productive water zone extends northward until it
meets the warm Atlantic, Indian, and Pacific waters.
n At this point, the cold Antarctic water sinks under the
warm water. This area is called the Antarctic
Convergence. It is located at approximately 50˚ to 60˚
south latitude.
n As in the Arctic, organisms living in the coldest
Antarctic ecosystems have special adaptations.
n Because the Antarctic is a relatively isolated
ecosystem, most species are specialized and found
only in the Antarctic.
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Chapter 16 Pages 16-33 to 16-37
Deep-Sea Ecosystems
Deep-Sea Ecosystems
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The Abyssal Zone
Chapter 16 Pages 16-33 to 16-34
Deep-Sea Ecosystems
n In the deep ocean beyond the continental shelves,
the sun’s light and warmth never reach the bottom
and the average temperature is 2˚C (35.6˚F).
 Without sunlight, there’s no photosynthesis;
consequently, there’s no primary productivity
in most of the deep ocean.
Viperfish
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Chapter 16 Pages 16-33 to 16-34
Deep-Sea Ecosystems
The Abyssal Zone
n Because there’s no primary productivity, most of the deep
ocean gets its nutrients from marine snow.
 Marine snow is the constant fall of sediment, dead
organisms, fecal pellets, and other nutrients from the
productive shallow waters above.
n Most of the deep ocean is the abyssal zone, which covers
about 30% of the Earth’s surface.
 This is one of the smoothest and flattest areas on Earth,
found at depths between about 3,000 and 4,000 meters
(9,843 and 13,123 feet).
 Without primary productivity, the abyssal zone lacks dense
life concentrations. However, there’s a vast species diversity.
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Chapter 16 Pages 16-33 to 16-34
Deep-Sea Ecosystems
The Abyssal Zone
n Marine snow makes the deep ocean rich in nutrients.
However, the nutrients are spread out evenly.
 Without photosynthesis, there’s insufficient energy
accumulated to support a great abundance of
multicellular organisms.
 Those that do survive are primarily
echinoderms, such as sea cucumbers, sea
lilies, and brittle stars.
 Concentrations of large organisms are rare.
However, submersibles have seen rattails, deepsea dogfishes, catsharks, crustaceans, mollusks,
and many species of deep ocean fish.
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Chapter 16 Pages 16-33 to 16-34
Deep-Sea Ecosystems
The Abyssal Zone
n The greatest diversity in the abyssal zone is found in
the meiofauna.
 As in beach sand, you can find representatives
from almost all the animal phyla living in the deep
ocean mud or sediment.
 The concentrations and populations are lower
than in shallower seas, but the diversity is not.
 Scientists have explored only a small portion of
the abyssal zone. It is not unusual for new species
to be found there. It is one of the last frontiers on
Earth to be explored.
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Whale Falls
Chapter 16 Pages 16-34 to 16-35
Deep-Sea Ecosystems
n Although the abyssal plains are typical of most of the
deep-ocean ecosystems, there are some important
exceptions, including whale falls.
 A whale fall is exactly what the name says - a
place where a dead whale comes to rest on the
deep ocean floor.
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Chapter 16 Pages 16-34 to 16-35
Deep-Sea Ecosystems
Whale Falls
n Whale carcasses provide a massive concentration of
nutrients in areas that normally only receive diffuse
marine snow.
 Scientists think that the result is the development
of a distinct local ecosystem that goes through
three distinct stages.
n The first stage is when the scavengers arrive.
 They consume the whale’s soft tissues in a few
months. Hagfish, grenadiers, deep-sea spider
crabs, and sleeper sharks are some of the
scavengers associated with this stage.
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Chapter 16 Pages 16-34 to 16-35
Deep-Sea Ecosystems
Whale Falls
n The second stage lasts about a year.
 Worms, small crustaceans, and other small
organisms feed on the remaining soft tissue and
the tissue dispersed around the whale as detritus.
 Marine biologists are still trying to determine
exactly how these organisms find their way to the
whale.
 The current thinking is that the larval stages for
these animals is widely dispersed, and settle on
food when it becomes available to complete
development.
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Chapter 16 Pages 16-34 to 16-35
Deep-Sea Ecosystems
Whale Falls
n The final stage involves the decay of the whale
skeleton.
 This can last several years or even decades. The
bones provide a steady supply of sulfide as they’re
broken down.
 Chemosynthetic bacteria live on this sulfide,
creating a food source for tubeworms,
crustaceans, gastropods, and bivalves.
 These bacteria appear to be the same as those
associated with hydrothermal vents. It may be that
whale falls enable the colonization of these deepsea ecosystems.
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Whale Falls
Chapter 16 Pages 16-34 to 16-35
Deep-Sea Ecosystems
n If this is the case, the effects of whaling on these
deep ecosystems may be substantial.
 Other large organisms sinking to the deep ocean
bottom have a similar effect.
 Wood, kelp, Sargassum, and large fish provide a
nutrient concentration that supports a local
ecosystem for several months to a year.
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Chapter 16 Pages 16-35 to 16-36
Deep-Sea Ecosystems
Hydrothermal Vents and Cold Seeps
n Hydrothermal vents are sources of primary
productivity.
n Around these vents, chemosynthesizing bacteria
consume sulfides dissolved in the heated water
emerging from these vents.
n These bacteria act as the base of a trophic pyramid
for a diverse community living in these deep ocean
ecosystems.
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Hydrothermal Vents and Cold Seeps
Chapter 16 Pages 16-35 to 16-36
Deep-Sea Ecosystems
n Similar to hydrothermal vents, cold seeps are areas
where hydrocarbons and sulfide-rich fluids seep from
the underlying rock in the ocean floor.
n These are called “cold” seeps because they’re cool
compared to hydrothermal vents.
n However, they are heated by geothermal energy from
inside the Earth.
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Hydrothermal Vents and Cold Seeps
Chapter 16 Pages 16-35 to 16-36
Deep-Sea Ecosystems
n Like the hydrothermal vents, cold seeps support
chemosynthetic-based ecosystems.
n The chemosythesizers include the same sulfideconsuming bacteria, but other vents and seeps rely
on microbes that consume methane or other
hydrocarbons.
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The Hadal Depths - Ocean Trenches
Chapter 16 Page 16-36
Deep-Sea Ecosystems
n The hadal zone makes up the deepest ocean
depths, found in the deep ocean trenches where the
oceanic plates collide with continental plates.
 Depths in this zone range from about 5,000 to
6,000 meters (16,400 to 19,700 feet), although
some spots are deeper than 11,000 meters
(36,000 feet).
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Chapter 16 Page 16-36
Deep-Sea Ecosystems
The Hadal Depths - Ocean Trenches
n Scientists know little about the hadal zone
ecosystems primarily because of the limits of
technology.
 The extreme pressure makes it expensive and
difficult to make submersibles or instruments
capable of observing these depths.
 Only a few submersibles have been built that can
descend safely into the hadal zone, and only a
single manned trip has been made to the deepest
known spot in the ocean.
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n Therefore, what scientists know about life in the
hadal zone is limited to fleeting glimpses.
 Most of these are from ROVs (Remote Operated
Vehicles) and brief visits by submersibles.
 These brief observations have found organisms
even in the Mariana Trench (the deepest known
place on Earth), but the character and extent of
the hadal ecosystems remain largely unknown.
Chapter 16 Page 16-36
Deep-Sea Ecosystems
The Hadal Depths - Ocean Trenches
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