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[Music]
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what autoroes support the largest food
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web in the world single-sellled
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planktonic marine autoroes such as
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datoms dinoflagulates cocoalithophores
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and bacteria These organisms provide 90
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to 96% of the ocean's photosynthetic
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sugar production And the ocean food web
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is the largest food web in the world
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That means these organisms support the
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majority of the world's ecosystems Let's
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review what all photosynthesizing
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autoroes on our planet have in common
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Chlorophyll Chlorophyll is a green
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pigment which means it absorbs all light
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colors except green which it reflects
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There are a number of different types of
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chlorophyll pigment but all
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photosynthesizing autoroes have at least
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one of them This is a problem for
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organisms that live in the deeper
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coastal ocean environment where only
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green light is available Since
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chlorophyll will not capture this green
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light another pigment is needed to do so
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We call these extra pigments accessory
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pigments and we use the color of these
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pigments as well as other differences to
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classify the multi-selled seaweeds that
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live in the coastal environment Brown
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algae includes kelp such as in this
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picture and they contain brown accessory
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pigments Red algae contain red accessory
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pigments and green algae contain only
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chlorophyll but a number of different
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types Net result green algae cannot
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survive in the deeper coastal ecosystems
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because they require light other than
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green They are typically found in the
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highest levels of the inner tidal
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environment Red algae dominate the
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middle inner tidal zone and brown algae
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the lower zone Plants also have only
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chlorophyll but because they have the
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added challenge of roots and need to get
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their nutrients and water through these
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roots they are relegated to the upper
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inner title zone and consist only of
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grasses and mangrove
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trees These multi-selled marine autoroes
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plants and seaweeds account for only 4
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to 10% of the marine photosynthesis
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Remember most of it comes from the
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single-sellled organisms Let's review
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some of those important organisms
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starting with
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bacteria Marine bacteria are
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single-sellled proarotes with no nucleus
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and the simplest cell structures However
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they play a number of important roles in
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the ocean In addition to photosynthesis
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they also act as decomposers and
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nitrogen fixers The dominant form of
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nitrogen in the ocean is nitrogen gas a
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form that is unusable by most marine
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organisms That gas has to be converted
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first into nitrate ions before it can
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diffuse into an autoro and be used for
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growth It is a limited but very
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important nutrient Of the remaining
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single-cellled
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photosynthesizing three important ones
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are datoms cocalithophores and
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dinoflagulates
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Datoms are single-sellled protista with
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a solicious shell made of Si O2 They
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come in a number of different shapes and
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sizes including centric and penate forms
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as well as pillows and chains Chains are
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made up of centric datoms that connect
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together into larger units These larger
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units can be ramrod straight curved or
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completely baldled up The protrusions
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you see in these pictures of datoms from
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San Francisco Bay are glass spines they
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use among other things to increase their
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surface area and help themselves stay
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afloat As most datoms are planktonic
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shells of dead datoms that have
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collected on the seafloor contribute
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greatly to solicious
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oozes Cocoithophores are single-sellled
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protista with a calcium carbonate shell
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made of many doughnut-shaped plates They
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have two fleella they use to move around
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and a hyponym they use to capture
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nutrient molecules They too are
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planktonic and their shells contribute
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to calccarious oozes on the
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seafloor Dinoflagulates are
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single-sellled protista with no shells
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Most dinoflagulate species are autoroes
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but there are also some that are
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heterroes They have a thick cellulose
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outer cell wall and two fugella that
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they use to change their direction in
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the water As they cannot swim faster
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than currents they are also referred to
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as plankton Because they have no shells
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they do not contribute to seafloor oozes
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or
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sediment Plankton can be subdivided into
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arophic plankton referred to as
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phytolankton and heterotrophic plankton
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referred to as zoo plankton Datoms
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cocoalithophores and dinoflagulates are
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three important phytolanton organisms
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found across the world's
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oceans Pause
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[Music]
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Now let's talk more now about
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photosynthesis We can measure the amount
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of carbon produced daily by
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photosynthesizing organisms in a given
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area We call the total amount produced
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gross primary
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productivity If you subtract the amount
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of sugar that gets consumed through
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respiration by those same organisms to
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supply their own metabolic needs
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including growth and reproduction the
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result is called net primary
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productivity Very similar to gross
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salaries and net salaries which have had
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all the taxes and benefit contributions
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removed
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Is the amount of photosynthesis the same
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everywhere in the oceans no Why not
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there are certain factors necessary for
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photosynthesis that are absent in many
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parts of the oceans These factors limit
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photosynthesis in those areas Thus we
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call them limiting factors The two
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largest limiting factors to marine
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productivity are sunlight and nutrients
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Sunlight is present only in the photoic
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zone which can be significantly reduced
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by suspended sediment or high amounts of
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plankton in the water Sunlight
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availability also decreases
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significantly in the poles during their
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winter months when some of the areas
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receive absolutely no sun During summer
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in those same areas there can be 24
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hours of sun What about nutrients
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nutrients are trapped at depth in areas
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where there are well-developed picnic
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lines Nutrients can return to the
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surface only when there is upwelling or
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river runoff The picnoclines form when
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surface waters warm so much they
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separate from deeper cold waters That
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happens in the equatorial and tropical
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oceans all year round It happens in the
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temperate latitudes in the summer
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There's never a picnic line at the poles
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because there's never enough sunlight
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there to produce one The compensation
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depth is the depth at which net primary
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productivity equals zero It is also the
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base of the photoic zone It represents
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the lower limit of where autoroes can
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survive in the oceans Though
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photosynthesis can still happen below
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this depth there's not enough light to
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produce enough sugar to provide the
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autoro's own daily needs The
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compensation depth increases in summer
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as the amount of direct sunlight hitting
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the surface increases It decreases in
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winter when the sun appears for less
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time each day and at a shallower angle
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Deepest photoic zones and compensation
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depths happen when the picnic line is
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most developed Maximum sunlight but
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minimal nutrients In winter we have the
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opposite No picnicline maximum nutrients
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minimal
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sunlight Based on the availability of
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sunlight and nutrients where would you
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expect productivity in the oceans to be
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high productivity should be high in the
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poles during the summer Plenty of
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sunlight and nutrients no picnic line
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The sudden presence of both limiting
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factors to an area often will
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precipitate a bloom or rapid growth of
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plankton and high biological
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productivity The summer plankton blooms
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at the poles are the largest in the
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world's oceans In the tempered oceans
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productivity is highest in spring and
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fall The peakline that develops in
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summer traps the nutrients at depth The
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limited sunlight in winter diminishes
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productivity then So only just before
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the picnic line develops or just after
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it disappears will both sunlight and
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nutrients be available in abundance In
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temperate regions we get a large spring
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bloom and a smaller fall
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bloom In equatorial and tropical regions
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where there is always a picnic line
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there will be no productivity in the
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waters unless as previously mentioned in
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areas of upwelling or river runoff as
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long as sunlight is sufficient as well
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biological productivity can be quite
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high
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We can use chlorophyll abundance to get
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an idea of general productivities You'll
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see red and yellow is the highest
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productivity showing up along coasts
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near deltas and in the polar oceans
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during summer Green the next highest
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productivity appears in areas of
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upwelling such as where the North
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Atlantic deep water wells up north of
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Antarctica and in the eastern equatorial
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zones where the trade winds pull the
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surface waters offshore such as off
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California and Peru and the west coast
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of Africa
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Productivity is low in the equatorial
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and tropical
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oceivity that results from high nutrient
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runoff along the
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coast Pause now
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[Music]
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Sometimes the blooms that are triggered
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by an influx of nutrients contain
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organisms that emit toxins that can kill
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other organisms We used to call these
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red tides but as they have nothing to do
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with the tide now they're referred to as
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HABs or harmful algaal blooms The
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primary culprits are some species of
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dinoflagulates and datoms Typically
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these organisms have a dark brown or
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reddish pigment so they will cause the
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water surface color to change when
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they're present in high amount Some of
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the toxins emitted by these organisms
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are neurotoxins that can cause paralysis
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or respiratory failure and can enter the
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animals through ingestion or inhalation
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of sea spray It is for this reason that
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during an HAB you should stay out of the
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water and close shellfish industries in
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the area until the HAB has disappeared
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and the filter feeders have had time to
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eliminate the toxins from their
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system Natural and human dumped toxins
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in the marine environment such as
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pesticides and heavy metals can be
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absorbed by aroes and then transferred
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up the food web to different trophic or
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feeding levels accumulating in each
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level in increasingly greater and
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greater amounts We call this
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biomagnification These toxins accumulate
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in an organism because they are ingested
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faster than they can be expelled by the
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body's natural waste
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processes In open ocean food webs
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roughly 10% of the energy available in
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one organism is transferred to its
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consumer The rest is lost in heat energy
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or waste material There's a lot of
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energy loss in this process and a lot of
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accumulation and magnification of toxins
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We call the first level of this pyramid
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trophic level one the second trophic
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level two and so on Coastal regions have
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a slightly higher energy transfer
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efficiency
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15% Areas of upwelling are even higher
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20% The lowest efficiency of transfer
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happens between sunlight and autoroes at
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trophic level one Only 2% of the energy
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available in the sunlight absorbed by
00:11:55
chlorophyll is transferred to sugar
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production 98% is lost
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As this picture demonstrates to support
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one average human body mass eating
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salmon you'd need 10 times your body
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mass in salmon which would mean a 100
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times your body mass in herring which
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means a thousand times your body mass in
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zohoplankton and 10,000 times your body
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mass in autoroes like
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datoms Pause now
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[Music]
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This image of a food web shows a more
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realistic view of eating habits where
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each organism eats meals from various
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trophic levels Much of the zohop
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plankton includes laral organisms
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present only until they grow big enough
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to swim or sink and attach to the bottom
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or crawl away These laral organisms
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include fish crabs clams and sea
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cucumbers We call organisms that live as
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plankton for only part of their life
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cycle maroplankton If an organism is
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planktonic through its entire life cycle
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we call it holoplankton It spends its
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whole life as
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plankton Let's highlight some examples
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of both Starting with some examples of
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meoplankton This image shows the life
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cycle of jellyfish The adult form is
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planktonic and releases egg and sperm
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into the water column to reproduce These
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get together in the planktonic
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environment and develop into a laral
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form that sinks to the bottom of the
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seafloor and attaches now a benthic
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polip As the larve evolve in this polip
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form they generate many buds that
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eventually release themselves and swim
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away back into the plankton world Other
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examples of meoplankton include laral
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barnacles such as this one which when
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full grown will also sink to the
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seafloor attach and become cesile
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benthic barnacles And once a year coral
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reefs emit egg and sperm into the water
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column where they develop into larve
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that sink to the bottom of the seafloor
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And if the environment is right to
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develop a coral a new coral reef
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community will form
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As for holoplankton again there are many
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different varieties We've already
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discussed the datoms dinoflagulates and
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cocoalithaphors of the phytolankton
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variety Now let's explore four examples
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of zohop plankton that spend their
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entire lives as plankton Starting with
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two single-sellled protista radolaria
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and foraminifera Both of these organisms
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contribute to oozes on the bottom of the
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seafloor Radaria with silica shells and
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foraminifera with calccarious shells The
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shells as you see in these images can be
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quite spectacular with ornate designs
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spines and holes The cell wall of these
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organisms can be extruded through these
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holes like bubbles to engulf and trap
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prey much like an
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amoeba This picture shows a
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single-sellled form eating a
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multi-selled copapod trapped on its
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spines Copapods are an important animal
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in the holoplankton community They are
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arthropods very similar to crabs but
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spending their whole lives in small
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planktonic form Like all arthropods
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copapods have an exoskeleton they must
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shed in order to grow We call this
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process molting And you can imagine that
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much of the detritus that falls to the
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seafloor will be composed of copapod
00:15:26
molts These organisms create currents
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that move water along their bodies and
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they use their psyia covered appendages
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to filter food out of the water A
00:15:36
complete list of heterotrophic
00:15:38
holoplankton should also include
00:15:40
nautilloids
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ostracorms tintinets and
00:15:46
rotifers What about jellyfish how do
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they fit in jellyfish are multi-selled
00:15:51
meoplankton These nidarian have
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tentacles that surround a single opening
00:15:57
Tentacles all have stinging cells and
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the body creates a hollow pouch in which
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all food and waste are processed
00:16:03
Jellyfish are plankton because while
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they can move vertically through the
00:16:06
water column they cannot swim
00:16:08
horizontally faster than currents So
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they are at the whim of currents There
00:16:13
are many types of jellyfish in the
00:16:14
oceans including common varieties like
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sea nettles and moon jellies Some like
00:16:19
this variety shown here by the wind
00:16:21
sailors are made of communities of
00:16:23
individuals that all grow together to
00:16:25
create a single organism These are part
00:16:27
of a regular beaching event that can
00:16:29
happen when large groups of these
00:16:31
jellyfish get caught up in strong
00:16:33
currents or winds and blown or pushed
00:16:36
onto the
00:16:37
beach Pause now
00:16:43
[Music]
00:17:30
[Music]
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[Music]
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[Music]
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[Music]
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[Music]
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[Music]
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[Music]
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[Music]
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[Music]
