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today's video is sponsored by klima
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the deep sea can be a barren realm
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with increasing depth we find an
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exponential decline in biomass which has
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driven creatures of the deep to adapt in
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weird and wonderful ways
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generally these organisms must rely on
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marine snow as a source of food
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a trickle of fecal pellets and dead
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organic material that drifts downwards
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from the surface waters
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where photosynthetic primary
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productivity is possible
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below 200 meters
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levels of ambient light from the sun are
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too low for photosynthesis to occur
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and at around 1 000 meters aside from
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the infrequent twinkling of
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bioluminescence
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the ocean is drowned in pure darkness
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[Music]
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without photosynthesis the supply of
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scraps are all that remain to nourish
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any life
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[Music]
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however on the deep sea floor there are
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important regions where primary
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production is possible via a different
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mechanism called chemosynthesis
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these are the chemosynthetic oases of
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the deep sea which represent some of the
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only locations on earth where the
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ultimate source of energy for life is
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not sunlight but the earth itself
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in this series of films we'll delve into
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their formation and ecology
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as well as the threats they face and the
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importance of stewardship for these
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fascinating environments
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[Music]
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[Music]
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[Music]
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the process of chemosynthesis is similar
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to photosynthesis
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both can be defined as the creation of
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organic matter
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from the fixation of inorganic carbon
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using energy
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but what differs is the source of that
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energy
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in parts of the deep sea primary
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production is fueled by chemical energy
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rather than energy from the sun
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but this can only take place at certain
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sea floor environments
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where the required chemicals are
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released into the water
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the two main examples of such
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environments are hydrothermal vents and
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cold seeps
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the former were only discovered in 1977
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when scientists were exploring an
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oceanic spreading ridge near the
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galapagos islands
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what they discovered was a hidden world
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that revolutionized our understanding of
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how and where life on earth can exist
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[Music]
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since then hundreds more vent fields
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have been discovered often at depths of
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two kilometers or more
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along earth's convergent plate
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boundaries and at sea floor spreading
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regions where the oceanic crust is
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moving apart
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one major site of high vent abundance is
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the east pacific rise
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where the fast spreading rates have
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created event fields dotted along the
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ridge
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tens of kilometers apart
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in contrast the vent fields of the much
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slower spreading mid-atlantic ridge may
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be hundreds of kilometers apart
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[Music]
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they form here because the rifting of
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tectonic plates creates fissures in the
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crust and allows hot magma from deep
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within the earth to rise closer to the
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seabed
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upper parts of the sea floor are very
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permeable cold sea water enters and
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percolates down through the crust where
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it becomes superheated and takes up
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minerals from the surrounding rocks this
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mineral-rich fluid then jets back into
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the ocean at extremely high velocities
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and temperatures exceeding 400 degrees
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celsius
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as the fluids mix with cold sea water
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the dissolved minerals precipitate out
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in smoke-like billows
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and build towering chimney structures on
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the sea floor
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[Music]
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there are a few varieties of
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hydrothermal vent characterized by the
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specific mineral content of the vent
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fluid
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black smokers emit the hottest darkest
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plumes
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forming chimneys over 50 meters tall
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with high levels of sulfides that
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precipitate on contact with the cold
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ocean
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to form the black smoke
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in contrast white smokers contain barium
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calcium and silicon
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other vents may be characterized simply
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by shimmering streams of water
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[Music]
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although the throat of vent chimneys can
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reach around 400 degrees celsius
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there is a very sharp temperature
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gradient between the fluid and the
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surrounding seawater
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across a distance of around 10
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centimeters temperatures can drop from
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over 300 degrees to just 2 degrees
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celsius
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most vent animals live at far cooler
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temperatures but prokaryotic microbes
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including forms of both archaea and
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bacteria are able to tolerate fluids as
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hot as
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122 degrees celsius
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here they carry out chemosynthesis via a
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number of different pathways that depend
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on the specific conditions of their
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microenvironment and the chemicals that
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are present
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typically they use energy stored in the
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chemical bonds of hydrogen sulfide and
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methane to create glucose from water and
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dissolved carbon dioxide
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the result of this chemosynthetic
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primary productivity is the presence of
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vast assemblages of animal life
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concentrated at these regions
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[Music]
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the supply of nutrients forms the basis
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of a food web for a diverse community of
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specialized organisms
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[Music]
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an oasis of life in the deep
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[Music]
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to understand just how significant these
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communities are you only have to compare
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the life of hydrothermal vents with
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non-chemosynthetic deep-sea environments
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[Music]
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out on the abyssal plain life is present
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but scattered
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animals must spread out in order to
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stand a chance of gaining enough
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nutrients from marine snow to sustain
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themselves
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but at the vents the chimneys are
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encased with dense colonies of
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rust-colored snails
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swarms of deep-sea shrimp
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or expansive aggregations of ghostly
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white crabs competing for space on the
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rocks
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remarkably these varied and abundant
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species are all sharing a single
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resource
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they all rely on the chemosynthetic
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microbes as a source of food
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meaning vents are sites of significant
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interspecific competition
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that is competition between members of
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different species
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often interspecific competition can lead
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to the extinction of one or more of the
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species competing
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the species that is less suitably
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adapted may lose out on the resources it
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requires and become out-competed
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[Music]
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the idea that in a stable ecosystem no
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two species can have exactly the same
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niche and stably coexist is known as the
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competitive exclusion principle
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[Music]
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but when this doesn't lead to extinction
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interspecific competition can instead
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cause specialization of the different
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animals
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a phenomenon called resource
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partitioning occurs where species with
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overlapping fundamental niches evolve
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different adaptations
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it allows the species to co-exist
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because there is less direct competition
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between them
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this is what occurred at hydrothermal
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vents to make them so stable
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the competing crabs worms and shrimps
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may all be in pursuit of the same
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resources
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but they have developed very different
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ways of acquiring them
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[Music]
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squat lobsters and limpets graze the
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microbial mats that surround many of the
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chimneys
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we also find suspension feeders like
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deep sea mussels feeding on free living
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microbes that are suspended in the water
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yeti crabs farm the bacteria in
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filamentous hair-like colonies on their
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bodies
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reducing the pressure on the crabs to
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compete for space with other species
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like shrimps
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[Music]
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the crabs are able to move around and
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take the bacteria with them
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with the microbes acting as epibionts
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inhabiting their surface
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[Music]
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giant tube worms are sessile
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meaning they are fixed in one place and
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cannot move their competitive advantage
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arises from their ability to form an
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endosymbiotic relationship with the
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microbes
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they store them within their tubes
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effectively holding them captive and
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benefiting from the nutrients they
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produce
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the worms take up hydrogen sulfide and
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other chemicals from the vent fluids in
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order to feed the bacteria
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in return the bacteria provide the
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carbon that the tube worms require in
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order to live
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it is also thought that the bacteria
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benefit by being sheltered within the
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tube worms and are therefore protected
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from predatory grazers like limpets and
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crabs
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another denizen of deep sea vents the
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pompeii worm farms bacterial colonies in
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a similar fashion to yeti crabs
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but its higher thermal tolerance allows
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it to inhabit locations on the vent
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structures that are far hotter than
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those that the crabs can endure
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here they dwell within u-shaped tubes
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which can reach temperatures up to 80
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degrees celsius
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[Music]
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thus much like we see with creatures of
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the rocky intertidal zone
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there is zonation here between different
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animal species
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which occurs due to the presence of a
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temperature gradient and varying
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abundances of different microbe
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varieties
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[Music]
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in a way
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the worms and crabs have become
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geographically isolated from one another
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within the same vent system
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all the creatures we've discussed so far
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can be classed as primary consumers
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but organisms from higher trophic levels
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are also present
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the octopus for example is one of the
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top predators of deep sea vents
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along with white zoar kid fish which
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feed on the tube worms and shrimps
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some deep sea skates which tend to dwell
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along the continental slope visit
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hydrothermal vents to feed
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but also to lay their eggs
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they do so in order to use the volcanic
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heat to accelerate egg development
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and reduce the usually years-long
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incubation time
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the zonation of life advance leads to a
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higher abundance of filter feeders and
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predators in the periphery further from
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the chimneys
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animals like stalked barnacles and
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predatory anemones are less tolerant of
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the chemical rich low oxygen conditions
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found closer to the fluids
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but they can still make a living here
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beyond the periphery we find non-vent
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deep sea fauna existing on the abyssal
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plain near the vent systems at higher
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abundances than they're typically found
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this is because even hundreds of meters
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away from the vent itself animals can
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still make use of some of the exported
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organic matter
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[Music]
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in all over 590 animal species have been
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identified living at hydrothermal vents
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and a surprising majority of these
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organisms are unique to this environment
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having become specialized in such a way
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that means they rely entirely on the
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chemosynthetic conditions of the vents
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[Music]
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the discovery of deep sea hydrothermal
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vents was groundbreaking for another
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reason
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their unique conditions the abundant
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nutrients of these chemical gardens led
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to scientists speculating whether these
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vents could be where life on earth
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originated
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although unproven there is substantial
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evidence to suggest this may be the case
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firstly some of the thermophilic or
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heat-loving vent microbes are among the
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most primitive organisms known on earth
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evidence is also given by the fact that
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many of the chemical building blocks of
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life are found at the vents suggesting
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that the precursors of life harnessed
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carbon dioxide and hydrogen available in
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those primitive conditions to create
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complex organic molecules such as amino
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acids and nucleotides
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in conclusion hydrothermal vents support
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unique ecosystems and their communities
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of both highly specialized as well as
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simple organisms in the deep ocean
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the islands of abundance they create in
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the otherwise barren depths are sites of
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outstanding scientific interest
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providing a new insight into what is
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truly necessary for life to survive
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[Music]
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but they are not the only major
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chemosynthetic oases in the deep sea
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in part two we'll explore the life of
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cold seeps or cold vents
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these are regions where cold hydrocarbon
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rich water escapes from the ocean floor
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hosting their own distinct assemblages
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of life
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and forming peculiar landscapes at the
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bottom of the ocean
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[Music]
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today's video is sponsored by klima
00:18:18
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[Music]
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you
