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Chapter 12 — Transcript

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0:00Hi there, I'm Dr. Jeff Ashley and
0:02welcome to chapter 12. In the last
0:04quarter of the textbook, we shift our
0:06emphasis to biological oceanography.
0:08Chapter 12 deals with marine life. It
0:12deals with the classification of marine
0:13life and also the
0:17adaptations seen in marine organisms
0:20that make them perfectly suited for
0:22inhabiting the open ocean. Let's start
0:25off with the classification of life. For
0:28a long period of historic time,
0:30classification of organisms was based on
0:32physical characteristics alone. However,
0:35recently with DNA sequencing, we now can
0:38have genetic comparisons to add to our
0:42physical characteristics of
0:43classifications. So, what's a working
0:45definition of life? Living things can
0:49capture, store, and transmit energy.
0:52They have the capability for
0:53reproduction.
0:55They have the capability for adaptation
0:57to the environment and we'll see that in
0:59this chapter especially and they change
1:01or evolve over time. There are three
1:04domains of life. Bacteria which is
1:07simple life forms without
1:09nuclei. Archa which are simple
1:12microscopic creatures and uka complex
1:16multisellular organisms such as plants
1:18and animals. In that last domain, we
1:21have DNA which is specifically contained
1:24in a discrete nucleus. So you may be
1:26well aware of this from biology class or
1:28high school that there are six kingdoms.
1:31Archaoacteria, Uacteria, Protista,
1:35fungi, plante and anamelia. So ubacteria
1:39are the simplest organisms. These are a
1:41single-sellled lacking nuclei and they
1:44include cyanobacteria which is a large
1:47class of organisms that are in the
1:50marine environment. Archaobacteria are
1:53microscopic. They're
1:55bacteriaike. They include methane
1:57producers and sulfur oxidizers like
2:00those that we spoke of in the deep sea
2:02events. Remember those organisms, the
2:04bacteria that use H2S or hydrogen
2:07sulfide? That comes from this group.
2:09Most of these are ancient life forms on
2:12Earth. Plante are multi-selled
2:14photosynthetic plants such as surf
2:17grass, eel grass, mangroves, or marsh
2:19grasses. Anamelia are multi-selled
2:22animals and they range from simple
2:23sponges in the marine environment to
2:25complex vertebrates as we'll see.
2:27Protista, they're single-sellled and
2:29multi-selled with nuclei. They include
2:32algae and prozzoa. And lastly, fungi,
2:35mold and lychen. So early taxonomic
2:38classification was started by Lanaeus in
2:421758. He developed the basis for modern
2:45classification of organisms and he
2:47termed this
2:48taxonomy. Taxonomy is a systematic
2:51classification of organisms based on two
2:54characteristics. Early on it was
2:56physical characteristics but as I said
2:58the modern advent of DNA sequencing
3:01allows genetic information to come into
3:03play. Now taxonomy as you might have
3:06seen from biology class or high school
3:08once again ranges from kingdom narrows
3:11down to film from their class order
3:14family genus and the most specific
3:17subcategory is species. It's the
3:19fundamental unit and this is a
3:21population of genetically similar
3:24interbreeding individuals. You can see
3:27on the right just an example from our uh
3:30lovely friend here, the marine organism,
3:32the common dolphin. So, how do we
3:34classify marine organisms? Well,
3:37interestingly enough, there's only three
3:39broad categories. There's plankton,
3:42those organisms that have no ability to
3:44move by themselves. These are called the
3:47floaters.
3:49Nept so. So, we call them the swimmers.
3:52And then according to location, we have
3:54benthos, those bottom dwellers. Remember
3:56that term benthic, that adjective that
3:58refers to near the bottom or on the
4:00bottom. That's where it's coming from,
4:02benthos. So, let's start off with the
4:04first classification and that's
4:06plankton. Here it's the major biomass or
4:09amount of organic living organic
4:11material on Earth and this consists of
4:13plankton. Plankton is a very generic
4:16term and it might include phytolankton.
4:18These are autorophic organisms. They can
4:21synthesize and produce their own food.
4:23They're sometimes called primary
4:25consumers. Then we have zoplankton,
4:28another type of plankton, but these are
4:30heterotrophic. They rely on food
4:32produced by others such as
4:34phytolankton. These are called primary
4:37consumers. On the right, we have an
4:39image of various structures and species
4:42of both phytolankton, the autoroes, and
4:45zoplankton, the heterotroofes. We also
4:48have some other terms used with
4:49plankton. bacterial plankton. They're
4:52very small and it's estimated that at
4:54least half of the ocean's photosynthetic
4:56biomass comes from these organisms. It's
4:59likely the most abundant photosynthetic
5:01organism in the marine environment.
5:03Veroplankton are smaller than bacterial
5:06plankton. They're not well understood.
5:08If you look into the literature, people
5:10are still wondering about these species.
5:13They may limit the abundance of other
5:14plankton through infection. A couple
5:16differentiating terms here.
5:19Maroplankton are plankton that live part
5:21of their lives as
5:23planktonic organisms and the other half
5:26as juvenile or laral stages. On the
5:28right is an image that shows this. An
5:30organism such as a squid living part of
5:33its life as planktonic, but then as it
5:36ages and grows, it becomes uh it goes
5:40from the juvenile or laral stage into
5:42the adult stage. It's no longer
5:44considered plankton. It's actually now
5:47nectton. Compare that to halop plankton.
5:50These are plonic organisms that entirely
5:52live as plankton. I got this wrong. That
5:55sea figure at right should have been for
5:57me plankton. So this is a meoplankton
6:00example. Haloplankton would just be
6:02planktonic throughout their whole lives.
6:04Macroplankton as the name suggests these
6:07are large floaters such as jellyfish or
6:09sarasm. Early on in this course, I
6:12discussed sarasm off the coast of
6:14Florida and in the Caribbean. These are
6:16floating masses of plankton. We can see
6:19an image here. They have gas bubble-l
6:21like uh nodules that allow for buoyancy
6:24to keep them in the sunlit or photoic
6:27zone. Then there's picop plankton.
6:29Again, as the name suggests, these are
6:30very small floaters such as the
6:33bacterial plankton. As a little bit of
6:35an aside here, I do want to talk about
6:36bad plankton. And these are plankton
6:39that contain toxic compounds or have
6:42serrated edges on them. Toxic plankton
6:45is often called harmful algo blooms or
6:48habs. And it's common to hear every year
6:51about hab blooms in the Gulf of Mexico
6:55or off the coast of the Caribbean
6:57islands. Primarily the toxic nature from
7:00these plankton come from either the
7:03secretion or the body held toxin that
7:06resides in these organisms. Since they
7:09do have toxins, you can imagine that
7:11they are also represented on the food
7:13web or food chain. That organisms are
7:16interacting and ingesting these. Not
7:18only are they ingesting the organic
7:20matter as part of their body, but
7:21they're also ingesting that toxin and
7:24can travel through and up the food
7:26chain. These toxics may have different
7:29effects at each one of these levels.
7:31Toxic effects may even be seen in humans
7:34where some of these toxic compounds can
7:36be aerosolized and up in the air and
7:40breathed by humans on the shoreline. Not
7:42only can these toxic compounds be
7:45transferred up the food web in the
7:47pelagic or water column food web, but
7:50they can travel down and influence the
7:52benthic environment and those organisms
7:54living in it such as by valves and
7:56crabs. Here's an image of a red tide
7:59appropriately named because of the red
8:01co. And this is also known as an HAB, a
8:05harmful algo bloom. This one is
8:07specifically a microscopic algae
8:09specifically named Corinia brevvis and
8:13it commonly occurs off the coast of
8:15Florida in Texas in the Gulf of Mexico.
8:17Concentrated levels of this plankton
8:19make it appear that the water is red or
8:21bleeding. It causes this discoloration
8:24and also potentially harms marine life
8:26and also affects humans. As I said,
8:29here's an image of that specific
8:31species, Corenia brevvis. Let's watch
8:33this short
8:35clip. Red oceans might sound
8:37interesting, but red tides are not a
8:39good thing. Man-made pesticides and
8:42other chemicals people use are washing
8:44into our oceans and creating harmful
8:46algaal blooms. Some of these algaal
8:48outbreaks are toxic, killing marine
8:51animals, causing respiratory problems in
8:54human beings, and making some of our
8:56shellfish unsafe to eat. Our nation
8:59needs an integrated ocean observing
9:02system to help monitor these types of
9:04events which could be deadly. The Noah
9:07website will tell you where the
9:09particular blooms are. If I know where
9:11they are, I can avoid those areas.
9:13There's this fear that you're going to
9:15die. It's always in the back of your
9:16head because you can't breathe. The
9:18Florida red tide is a small microscopic
9:22harmful alcohol that produces a really
9:24potent neurotoxin.
9:27Beachgoers inhale that toxin. It's
9:30actually a trigger for
9:32asthma. We had a massive dolphin die
9:34off. The manatee, they're inhaling it as
9:37well. And they eventually do
9:41perish. Red tides when they come to our
9:44community affect us in so many
9:48ways. No one should get sick from a day
9:52at the beach. Our lifeguards are on
9:56their towers from 10:00 in the morning
9:58to 5:00 in the afternoon. When you see a
10:00bloom of red tide coming in, um, it has
10:03a a darker hue to the water. It kind of
10:06gives it a tanish kind of tint to it.
10:08The lifeguards are reporting on the wind
10:11speed and direction, respiratory
10:13irritation, the amount of dead fish on
10:16the beach. These are subjective reports.
10:19Would I like to see quantitative data
10:21instead of qualitative data? Yes,
10:24absolutely. If we had observing systems
10:28that were in our waters
10:3024/7 looking at the amount of toxin
10:33that's both in the air that we breathe
10:35and in the water potentially gliders or
10:38other AUVs mapping the bloom for us that
10:42gives the asthmatic the heads up and so
10:45the need to have the IUerving systems
10:49evaluate the harmful algo bloom status
10:52is really key to keeping people healthy.
10:54You know, we monitor the food we eat. We
10:56monitor the water we drink. Why couldn't
10:59it go over to monitoring our actual air
11:02quality that includes red tide? were
11:04blind as I'm not really knowing the full
11:07scale of what's
11:09although red tides and other toxic
11:11harmful algo blooms are summized to have
11:14always occurred their frequency is
11:16increasing and that may be due to
11:18increased runoff of nutrients from
11:21land-based or human-based activity or it
11:24could be from increases in the
11:26temperatures of these coastal systems.
11:28This is another planktonic species, but
11:31without secretreting toxic compounds, it
11:33does kill. And it does this by having
11:37spines with serrated edges, which can
11:39lodge into fish gill tissue, causing
11:42irritation, overp production of mucus,
11:44and eventual death. Our second
11:47classification after plankton was
11:49necton. These are independent swimmers.
11:51They have the ability to be mobile. Most
11:55adult fish and squid are necton
11:58including marine mammals and marine
12:00reptiles. These are the swimmers. And
12:02lastly, that broad classification after
12:04plankton and necton is benthos. Benthos
12:08is bottom dwellers. That includes epipa
12:11which live on the surface of the
12:12seafloor or infauna that live buried
12:15within the sediments of the ocean. also
12:18includes
12:19nectoodess which can swim or craw crawl
12:21through the water column above the
12:23seafloor. Benthos are most abundant in
12:25shallow water. However, many live in
12:28perpetual darkness, coldness and
12:29stillness in hydrothermal vent
12:31communities. Here we see some different
12:33species of benthos along the coastline
12:36and we see benthos and infauna. As I
12:39just mentioned, hydrothermal vent
12:41communities are a great example of very
12:43rich and diverse benthic communities.
12:45They're abundant and large deep sea
12:47ocean environments. They were discovered
12:50in 1979. As we saw before, they're
12:52associated with hot vents or these
12:55smokers. Bacteriaike
12:58uh organisms produce food in the absence
13:00of sunlight as we mentioned before and
13:03that fuels a whole complex ecosystem of
13:07organisms that thrive in the absence of
13:10light. So, let's just talk about the
13:12numbers of marine species. The total
13:15catalog numbers of species on Earth is
13:17around 1.8 million. However, that number
13:20is still constantly increasing. Many of
13:23these marine species have not been
13:24identified due to the difficulties in
13:27actually finding them. As many as 2,000
13:30new marine and terrestrial species are
13:32discovered each year. It's interesting
13:34that more land species exist or have
13:36been identified than marine species. The
13:39ocean has a relatively uniform
13:41condition. There's less adaptation
13:43required, so less divergence or less
13:46speciation. Marine species
13:48overwhelmingly are benthic. 98% of them
13:51are benthic rather than pelagic. That's
13:54because benthic environments have more
13:56habitats for which organisms can adapt
13:58and evolve. They are more diverse than
14:00the water column. The Census of Marine
14:03Life was a program that put a lot of
14:05money into identifying over a 10-year
14:08period the number of marine organisms
14:12that exist. They discovered that at
14:14least 1,200 new marine organisms,
14:16including the yeti crab, were actually
14:19out there. And they assessed the
14:21diversity, distribution, and abundance
14:23of these marine organisms. The World
14:25Registry of Marine Species has listed
14:28over 200,000 documented marine species.
14:32However, interestingly, only 13% of all
14:35known species on Earth are from are from
14:38the marine environment. And recall from
14:40an earlier slide that of that marine
14:43species, that 13% which is rather low,
14:46an overwhelming majority, 98% are
14:49benthic organisms as opposed to water
14:52column or pelagic organisms. So why so
14:55few marine species? The marine
14:57environment is much more stable or less
15:00diverse than the terrestrial environment
15:02or land environment. Marine conditions
15:04are pretty uniform. Marine animals have
15:06little selective pressure to adapt as
15:09opposed to those that have different
15:12environmental conditions on land. Ocean
15:15organisms are less able to withstand
15:17environmental changes. Land-based
15:20organisms are more robust and can adapt
15:22to those changes. So let's look at now
15:24adaptations of marine organisms. What is
15:27protoplasm? It's the colorless material
15:29comprising the parts of cell including
15:31the cytoplasm, the nucleus and organels.
15:35It's a substance of living matter. More
15:38than 80% of mass in organisms is water.
15:41And here we have a depiction looking at
15:44some organisms and comparing them to us
15:46humans. With so much water comprising
15:48their cells, marine organisms do not
15:51risk desiccation or drying out. As an
15:54adaptation, there has to be a physical
15:56support while living in water. There has
15:59to be some buoyancy sometimes or a
16:02resistance to sinking, especially for
16:05those organisms that want to
16:06photosynthesize and remain in the sunlet
16:09zone. So, different support structures
16:11exist in cold water versus warm water.
16:15Cold water is more dense and more
16:17viscous than warm water. We see that
16:20with organisms and their structures.
16:22Here we have a great example of that. In
16:25warmer, less viscous waters, this
16:29organism on the left, a warm water
16:32organism, has a whole bunch more
16:34appendages and body mass.
16:38It does that to actually allow itself to
16:42be maintained in the photo zone or the
16:45sunlit zone. In more viscous, more dense
16:49cold water, there's less appendages.
16:52That viscosity kind of like honey
16:54suspends it in the water column. So,
16:57this cold species, you don't see as much
17:00plumage or surface area in its body.
17:05Speaking of which, having a high surface
17:08area to volume ratio is good and that
17:10maintains buoyancy or for organisms that
17:14don't have
17:15motility. It allows them to remain in
17:17that sunlet zone before they start to
17:19sink out of it. Here's a great little
17:21example of comparing cubes. Cube A has a
17:25greater resistance to sinking because it
17:27has a high surface area to volume ratio
17:30as opposed to cube B and C. You can see
17:33that small organisms have large surface
17:36area to volume ratios which is good
17:38which keeps them suspended in water and
17:41resists the gravity force to sink.
17:45Having a lower surface area to volume
17:48ratio such as in this box crab at
17:511.5 determines that they will sink
17:53faster. Phytolankton can benefit from
17:56being in small.
17:58Phytolankton or plankton in general also
18:01can use appendages to increase the
18:04surface area. Remember many of these
18:07organisms are forming calccarious or
18:09solicious tests shells. So they create
18:12these shells in wonderful shapes to
18:16enhance the surface area to volume ratio
18:19to suspend them in the sunlight zone so
18:22they can maintain there especially for
18:23those wishing to photosynthesize. In
18:26addition to that, some of these species
18:29incorporate oil droplets to increase
18:31their buoyancy and suspend them in the
18:33water column for greater periods of
18:35time. Another interesting thing is when
18:37you're living in a highly viscous
18:39environment like water, certainly
18:41different from air where we can move
18:42around readily in water, especially cold
18:45water, which is very viscous as opposed
18:47to warmer water, you're up against this
18:50issue of trying to swim through that
18:52pool of honey. So here's where body
18:56structure comes into play. One thing is
18:59streamlining. And streamlining is an
19:01important uh adaptation for larger
19:04organisms to allow them to flow through
19:06this at times highly viscous fluid. At
19:09times meaning when it's very cold. They
19:12have flattened bodies and tapering back
19:14to minimize this wake or drag. So many
19:17types of marine organisms are
19:18streamlined to aid in their movement
19:20while swimming through the ocean. Let's
19:22talk about reproduction for a moment.
19:24One means of reproduction is broadcast
19:26spawning. And this is where eggs and
19:28sperm are directly released into the
19:30seawater. This happens with coral as an
19:33example down here where the release is
19:36widespread. It's like a cloud or a plume
19:39of both eggs and sperm that can be
19:41fertilized near that coral or um to
19:45adjacent communities. Marine organisms
19:47take advantage of water's high viscosity
19:50to enhance that reproduction chance.
19:52Let's talk about temperature and marine
19:54life. And we said that there's a narrow
19:56range of temperature in the ocean as
19:58compared to land. And we can see that on
20:00land there are days when we can start
20:03off early in the morning being very cold
20:05and it can get very hot very quickly. So
20:07that temperature range is huge.
20:09Organisms have to be adapted for that
20:12temperature change. In the ocean that
20:14doesn't happen. There are smaller
20:15variations both daily, seasonally, and
20:17annually. The deep ocean, in fact, is
20:20almost isothermal or the same
20:22temperature year round. So, why is the
20:24ocean more stable than the land? Well,
20:26there's four reasons for that. And we
20:28talked about this specific heat of
20:30capacity. Water has an enormous specific
20:32heat capacity, which means you have to
20:35input a huge amount of energy just to
20:38change one gram of that substance water
20:41one° C. It's unlike probably most of
20:46chemicals on Earth that allows it to
20:49remain at a temperature for a longer
20:52period of time. Ocean warming is reduced
20:54by evaporation. Evaporation allows
20:57sunlight energy or thermal energy not to
21:00be absorbed by the top of the ocean
21:02although that does happen but it allows
21:05it then to undergo a phase transition
21:07from liquid state to the gas state. So
21:10an input of that energy that energy is
21:12sort of sequestered in doing that phase
21:15transition rather than warming up that
21:17surface of the ocean. Solar radiation
21:20penetrates deeply into ocean layers. And
21:23also ocean mixing or the idea of
21:27non-mixing that these two layers don't
21:29readily mix um allows them to heat up
21:33the surface but not heat up the bottom.
21:35And the bottom is a huge volume of the
21:38volume of the oceans. So let's look at
21:40this cold water and warm water species
21:42difference. And we saw it in an image
21:44before. Floating organisms, the smaller
21:47the better, especially in warmer
21:49seawater. Warmer seawater is less
21:51viscous. So that less viscosity will not
21:55hold them in place but begin by gravity
21:57to make them fall. They want to remain
22:00there. So smaller is better. As we saw,
22:02a small surfacetovol ratio. The smaller
22:05you are, the better you are at remaining
22:07in that water column. And as we saw,
22:10more appendages will just sort of
22:12balloon and suspend them more. So you
22:16see these appendages like we saw in that
22:18uh image before of organisms, similar
22:20organisms that have more plumage or
22:22appendages to keep them in that warmer,
22:25less viscous, less dense seawater.
22:28Again, this is assuming that they're
22:30non-mobile. Uh tropical organisms grow
22:33faster, so metabolism increases, but
22:35they live shorter and reproduce more
22:37often. There are more species in warmer
22:39seawater, but there's more biomass in
22:42cooler seawater, especially in upwelling
22:44areas where nutrients are brought up. A
22:47couple terms I'd like you to know.
22:48Stenothermal versus eurothermal. So
22:51stenothermal organisms withstand very
22:54small changes in temperature. Typically
22:56live in the open ocean. So the open
22:58ocean the temperatures are not
23:00fluctuating that much and organisms are
23:03perfect for that area because they
23:05cannot withstand these uh large
23:07fluctuations in temperature. However,
23:09eurothermal organisms are ones that can
23:12actually withstand large variations in
23:14temperatures. Think of humans and these
23:17typically live in coastal or coastal
23:19waters. The same can be said for this
23:21salinity tolerance or intolerance. When
23:24you have something that's stell steno
23:27halaline, you have an organism that is
23:29withstanding only very small variations
23:31in salinity. They typically live in the
23:34open ocean because salinity doesn't
23:35change that much. Eurohaline organisms
23:38have this wide range of tolerance for
23:41salinity. They typically live in coastal
23:43waters for example like eststeries which
23:45receive inputs of fresh water at time
23:48and inputs of salt water at time. So
23:50fluctuations in salinity. These are the
23:53organisms that have adapted to that and
23:55thrive in these areas. Eurohaline.
23:58Little bit about osmosis. Water
23:59molecules move from less concentrated to
24:01more concentrated solutions. That's not
24:04like dusion. So less concentrated to
24:06more concentrated that induces an
24:09osmotic pressure. So in more
24:11concentrated solutions, this helps
24:13prevent the passage of water molecules.
24:15Couple things deriving from this. We
24:16have three new terms. Isotonic,
24:18hypertonic, and hypotonic. Isotonic is
24:22an organism's body fluid. Salinity or
24:26the number of salts dissolved in that is
24:29almost the same as the ocean. So an isot
24:32isotonic organism, its fluid salinity is
24:36about the same as its ambient ocean
24:38salinity. Hypertonic is when seawater
24:42has a lower salinity than an organism's
24:45fluid. And then there's hypotonic. An
24:47organism's fluid has lower salinity than
24:51the ocean. Just the reverse. So this
24:53comes into play this osmotic pressure
24:56and either water flowing into cells or
24:58out of cells in this uh issue of marine
25:01versus freshwater fish. In a freshwater
25:04fish as above, they are hypertonic
25:06relative to their environment and
25:08experience very high osmotic pressure.
25:11To counteract this, water is absorbed
25:13through the skin by osmosis. There are
25:16some salts being lost through the body
25:19and freshwater fish excrete large
25:21volumes of dilute urine. Just the
25:24opposite in saltwater fish, they are
25:26hypotonic relative to their environment
25:29and experience rather low osmotic
25:31pressures. So, they can secrete salts
25:34through their gills. There is loss of
25:36water by osmosis as well. and they
25:40secrete small volumes of very
25:41concentrated urine. The major difference
25:44is that freshwater fish do not drink
25:48water. However, saltwater or marine fish
25:52do drink large amounts of salt water. We
25:55mentioned this before, but gases can be
25:57dissolved in liquids and thankfully so
25:59because some of these organisms need
26:01oxygen. So animals can extract dissolve
26:04oxygen. They do this primarily through
26:06gill exchange where o oxygen is taken up
26:08and carbon dioxide is released directly
26:11into the seawater from that gill
26:13structure. When you have low oxygen
26:15levels that's called hypoxia or even
26:17zero oxygen concentrations which is
26:20anoxia that could kill fish. We saw
26:23before in the absence of any suspended
26:25solids or material like plankton water
26:28is fairly transparent. So many marine
26:31organisms see quite well. Some marine
26:34organisms are nearly transparent and
26:36this is so because they can elude
26:38predators or even stalk prey. There are
26:40other fascinating adaptations mentioned
26:42in this chapter. Two of them are
26:44camouflage and
26:46countershading. You can see on the left
26:48image camouflage and this is trying to
26:51match the colors of the ambient or
26:53background structures. Here counter
26:55shading is seen in a fish species
26:58halibet where on one side that halibit
27:01is dark and if you flip it over it is
27:03white. So imagine this fish trying to
27:06reside on the sediment. So it's going to
27:09have its dark side blend in with the
27:12darker sediment. So it is camouflaged to
27:16an extent from its predators. Having a
27:18very light side is great because when
27:20this fish is swimming and there are
27:21predators below, they see that white
27:24side and it blends in with all the white
27:26light coming. So, they're blending into
27:29that light background as opposed to the
27:32dark benthic environment. Fascinating.
27:34This is called countershading. So, this
27:36is a neat little sidebar. It's called
27:37deep scattering layer, DSL. This arrived
27:41from the Navy discovering through sonar
27:44reflecting the surfaces that that sonar
27:47was seemingly inferring that the bottom
27:49of the ocean was moving up and down
27:52significantly on a daily basis. Light
27:55versus night. It was around 100 to 200 m
27:58at night, but as deep as 900 m during
28:02the day. It wasn't the bottom of the
28:04ocean moving up and down. It was this
28:07large mass of organisms that were under
28:09growing undergoing a daily migration up
28:12and down the water column and it's these
28:14things called little copabods which do
28:17have the ability to be mobile. They were
28:19coming up to feed at night. So that
28:22meant that at 100 to 200 meters at night
28:25they were all up there in the absence of
28:28light they felt safer from their
28:29predator. During the day they would then
28:31descend to get away from their predator.
28:34So this is pretty interesting. This is a
28:36deep scattering layer. Back to
28:37differences in adaptations regarding
28:40this camouflage. There's also something
28:42called the disruptive coloration. And we
28:45see this often with tropical organisms
28:47like these fish. They have large bold
28:50patterns and caught contrasting colors.
28:52And this makes the animal blend into
28:55that complex background of a coral reef
28:58community. We've said this before and I
29:00hope I said it correctly. This was one
29:02of those fun facts that I wanted you to
29:03remember that the increase of one
29:06atmosphere and pressure for every 10
29:08meters of depth, I hope I said 10 meters
29:10and not one meter. For every 10 m of
29:12depth, which isn't that much, you
29:14increase the atmospheric pressure one
29:16atmosphere. This is why at the abyssal
29:19plane we talked about, pressures are
29:21extremely high because they're very
29:23deep. The adaptation to this is that
29:25many marine organisms have no inner air
29:28pockets. Those would collapse under that
29:30high pressure. Higher organisms like
29:32sperm whales have collapsible rib cages
29:34unlike ours which is rigid and would
29:37just implode under that high pressure.
29:40They can actually constrict that rib
29:42cage and survive with diving down deep.
29:45To deal with this water pressure, fish
29:48have swim bladders. Some fish have swim
29:50bladders that adjust the buoyancy and
29:52allows that fish to regulate depth. So
29:54divisions of the marine environment. We
29:56touched upon this before in marine
29:57provinces. There's this word called
29:59pelagic. Think of anytime you hear
30:01pelagic like a pelagic fish. Again, it's
30:04an adjective and it should suggest to
30:06you open ocean. Benthic is again
30:09relating to the bottom. So benthic. But
30:11the open ocean there's a nearshore and
30:13an offshore. So it's further subdivided.
30:16So that open sea close to shore is
30:19called narotic and further off is called
30:22oceanic. Okay. And I think we've seen
30:24these terms before. So narate pro
30:27provinces close to shore around 200
30:29meters in depth. So continental shelf
30:33oceanic provinces further beyond that
30:35beyond 200 m in depth. I don't expect
30:38you to know all these names. Again, I'm
30:40not testing you on this. But uh these
30:43are names that describe both the
30:45narratic provinces and the oceanic
30:48provinces and deliver also prefix names
30:51to that to suggest whether they're top
30:53pelagic around middle pelagic or very
30:57deep down called abyssopelagic. Uh we've
31:00seen this word abyssal before and even
31:03the deepest part here these are trenches
31:05is called the h had region. Oh, and I
31:07just have to play this out because that
31:09figure reminds me of Nemo.
31:19You better stay with me.
31:25So, we won't concern ourselves too much
31:28with these different zones, but I just
31:30want to mention again these prefixes to
31:33pelagic. So the upper part
31:36epipolagic uh a zone supporting
31:38photosynthesis meopilagic it's uh becom
31:41becoming dark so organisms have the
31:43capability of making their own light
31:45which is bioluminescence which comes
31:47from a chemical reaction. Further down
31:50we have ba pelagic and here is where you
31:54see a lot of bio bio luminescence
31:57happening. You also have something uh
31:59happening here with our dissolved oxygen
32:02versus depth. So this is another graph
32:04where we're calling this a depth
32:06profile. So starting at the surface
32:08going to the deep deep ocean, but we're
32:10monitoring here uh dissolved oxygen
32:12concentrations. Uh let's just look at
32:15dissolved oxygen oxygen concentrations.
32:18They are highest at the sea surface.
32:20Why? Because oxygen which is in the
32:22environment can readily pass through
32:25that air sea interface and be enriched
32:27in those surface waters. However, we
32:30know that there's organisms that are
32:32utilizing that oxygen. So, it quickly
32:35decreases with depth until we have an
32:37oxygen minimum right here. But it does
32:39rebound in the deep ocean here. So, the
32:41deep ocean, we said this before, is
32:43enriched with oxygen. What's happening
32:46here in the photo zone? We saw this in
32:48our activity with photosynthesis along a
32:52estuary that having oxygen here and
32:55sunlight and probably some nutrients. uh
32:58phytolanton are going to use those
32:59nutrients. So they knock the nutrient
33:01level way way down. That's because
33:03they're being utilized in the sunlit
33:05zone, but they are actually rebound
33:08here. As those phytolanton die and
33:11decay, they get eaten to an extent, but
33:13they die, decay, and fall. Bacteria
33:16chomp down that and instead of
33:18photosynthesizing, they do the opposite.
33:20they release all those nutrients again
33:24and they actually um will consume oxygen
33:27so that oxygen's at a minimum here. And
33:30I mentioned sunlight so it's time to
33:32bring up these terms again based on just
33:35sunlight penetration. There's something
33:37called euphotic and dysphotic and
33:39aphotic. Euphotic is the surface where
33:42enough lights exist to support
33:44photosynthesis. Dysphotic is ah you're
33:47beginning to really minimize that
33:49ability to transfer radio uh waves from
33:53the sun, electromagnetic waves from the
33:55sun, especially in the visible
33:57portion needed to
33:59photosynthesize and then you have
34:02aphotic which is the absence of any
34:04light. So as we get to see the bottom we
34:06get these prefixes with the bottom as
34:08well. Um but they are again pretty
34:11complex. Uh again, don't memorize any of
34:13this, but just know that that benthic
34:15environment could be nearshore. It could
34:18be uh way open ocean. And there are a
34:21whole bunch of new terms here. So, I'm
34:23just going to highlight it gets
34:25complicated. Not my intention to leave
34:27you with a whole word bank to memorize
34:29here. And again, as we get really,
34:30really deep, these words called uh
34:33abyssal and had come into play. When you
34:35hear them, think of the abyssal plane.
34:37Remember that area with fluffy fluffy
34:40sediment almost featureless um more than
34:4380% of the benthic environment is there.
34:45You can see abyssal tracks in the
34:47abyssal clay left behind in this image.
34:50And then very deep when you get into
34:52these deep ocean trenches area along
34:54continental margins where plates are
34:57coming together we have the hole region
34:59and that's below 6 km. All right that
35:01ends it for this chapter. It was again I
35:03got to use the term a whirlwind tour. We
35:06have entered biological oceanography and
35:08the remaining chapters will then zero in
35:11more with details on both plant and
35:13animals in the marine environment.

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