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Aloha welcome to our video on ocean
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productivity in here we'll list the
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factors that influence a region's
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photosynthetic productivity but also
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will describe Oceanic feeding
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relationships
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okay so let's look at productivity by
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location and when you're in productivity
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here we're talking photosynthetic
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productivity the first place we're gonna
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go is here to the tropics and in the
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tropics what we notice is we have this
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warm nutrient depleted surface water
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there's this thermocline that we talked
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about this temperature gradient and then
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we have this cool nutrient-rich water
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below now notice we have this nutrient
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rich water down here but it's blocked by
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this thermal climb from getting up to
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the surface so we don't get a lot of
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productivity in the tropics because the
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nutrients are already been depleted so
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even though there's a lot of Sun and we
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would expect to have a lot of
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photosynthesis there's not those
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nutrients that that phytoplankton needs
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for photosynthesis to occur so we don't
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see a lot of it happening there now if
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we go up to the temperate ocean regions
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and this is gonna be just outside of the
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tropics and up north a little ways what
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we notice is we have a couple spikes in
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productivity we're gonna have one here
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in the spring and then we'll have one
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here in the fall the one in the spring
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occurs because as winter comes and
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there's less sunlight in the temperate
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regions the nutrients are gonna be
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allowed to build up a little bit because
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there's less sunshine and we can see
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there less sunshine here that's gonna
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cause photosynthesis to go down and if
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there's no photosynthesis going down and
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there's no phytoplankton zooplankton
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have nothing to eat so there's not a lot
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of biological activity in the winter
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time but what we do see is as charging
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in the water at these nutrients as the
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Sun comes back in the springtime we
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notice a spike in phytoplankton which is
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gonna rise up here and then we followed
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by a spike in this so plankton will peak
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out here and what happens is is the
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nutrients start to deplete so that
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causes the phytoplankton to drop down
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the nutrients are down here and then we
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have this zou planktonic curve that
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catches up and that's what we see over
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the summer time so in the spring we see
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an awful lot of productivity in the
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summer time everything kind of balances
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out from that one and then in the fall
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we see a little bit of nutrient rise
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we're gonna see a little spike in the
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phytoplankton it's gonna cause a little
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bump in the soul plankton and then
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basically the whole level would crash
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except as the sunlight comes down to a
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certain point that's where we see the
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crash of photosynthesis that's gonna
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cause the crash of those animals that
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are feeding on those and we start seeing
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this winter buildup of nutrients again
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so that's how that cycle is going to
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continue
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now we're looking at these feeding
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relationships one of the interesting
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things to notice is and you should
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remember this from biology class that
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remember that not all the energy is able
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to transfer from one trophic level to
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the other remember trophic is just
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energy levels so here we're gonna build
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our little pyramid here and we're gonna
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make our pyramid gonna be five layers
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okay so we have three four and five so
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our first trophic layers that takes the
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energy from the Sun so here we have a
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half a million units of energy from the
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Sun coming through and only about 10,000
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that units is going to be converted to
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energy by this first one which is going
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to be our phytoplankton so through
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photosynthesis we're only trapping about
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10,000 units of radiant energy so here
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our trophic level 1 is where we're gonna
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find our phytoplankton ok and this is
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what's taking energy from the Sun now
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our phytoplankton is then gonna be fed
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on by Zoll plankton and we're going to
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see a transfer of about a thousand units
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and remember it's about 10 percents
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gonna transfer over so our trophic level
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2 is going to be made up of zooplankton
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okay and these feed on the phytoplankton
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from there we're going to see a hundred
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units transfer up to level 3 and that'll
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be our third trophic level and this is
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just gonna be let's call it just a small
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fish ok and that'll take us up to our
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next trophic level where we have 10% and
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again going through so that's only 10
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units are going to transfer to that one
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and here we'll have our big fish and
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then finally we get to the apex of our
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pyramid and here we're going to use us
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will use humans and notice only one
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energy so we're seeing half a million
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units of energy receive
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only ten thousand of it gets converted
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into this energy pyramid through
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phytoplankton and every step we take
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we're gonna lose 10% of that tempura
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snotty percent is gonna go into living
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and reproduction and things are there
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only ten percent gets moved on so for a
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half a million units of energy we as
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humans are only going to be able to get
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about one unit so you can see how it
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depletes as we go through
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ok the last topic we wanted to talk
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about our food chains and webs and again
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this is a review from biology class but
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notice that we're going to start off
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with our photosynthetic organisms down
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here and our photosynthetic organisms
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will then be consumed by a primary
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producer so we'll take the nice simple
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one will use a copepod right here and
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then our copepod is gonna be fed on by a
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secondary consumer and that would be our
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North Sea herring so a food chain shows
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us a very simple path of energy by
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consumption of what's going on so we
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start off with our photosynthetic
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organisms our producers and then we have
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our consumers moving up in the ocean it
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doesn't work that way at all in the
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ocean these photosynthetic organisms are
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going to be fed on by some so Plankton's
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they're gonna be fed on by some
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tunicates some mollusk larvae some
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assyrians those in turn are gonna be fed
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on by other organisms like amphipods and
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then up to the North Sea hearing which
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is gonna be our apex predator in this
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example so you can see a food chain is
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going to be a straight shot from one
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organism to another and it's chain looks
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like that and then when we link all of
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these together we end up with a food web
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that looks something like this one here
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ok so that's it for this video as always
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good luck on your quiz and we will see
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you in the next video
