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0:00
Welcome class. We're here for the first lecture of "Biology Marine Life --- OCB 1000c." We're going to start this course off with General Oceanography, because it's important to understand the habitat that these marine organisms live in.
0:22
Scientific inquiry; or the scientific method, is usually how we start off science classes. Now, the scientific method, although it's scientific (it is in the title) really, it's how we solve problems. In all of our classes, advertisers use it (with the Nielsen ratings and TV), and finding Target audiences and using demographics -- so science, and this does not refer to a class like a science class, but using a specific set of steps to solve problems. The picture,
1:02
here of course is our friend Bill Nye. Most of you should recognize him because he's a famous TV personality, scientist and what we're going to be looking at is what SCIENCE is --
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Like I said, there's some steps. Generally we use our powers of observation first, to
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spur interest. Maybe give some curiosity to what is causing a specific phenomenon and then we need to "State the problem."
1:41
Forming a hypothesis is an "If - Then"
1:47
hypothetical answer to that question (or problem) that is based on your observations. Then we test the hypothesis with an experiment, measure the data, analyze it and then draw our conclusions. So the scientific method is a systematic sequential series of steps used to explain things.
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First, the observation, is the hallmark of science. It's also the least reliable -- take a look at the arrows there. Without measurement your eyes tell you the bottom arrow is the longest, the bottom line would be the longest of those arrows -- but in reality they're all the same length. So you need to measure your observations after you observe them. The picture below, that is a famous one, one of those hidden pictures. You can see an older lady or a younger lady depending
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on how you look at it, and then different people see different things. So everybody's observations may be different and that's why measurement and clear testing is important.
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So hypotheses are the statement that will explain your observations, but they have to be able to be tested -- they're a prediction as to what the results of that test will be and we generally write them in an "If - Then" format. Experiments then, you have a control group. That control group is lacking what you're testing. That sets the baseline to what your data should be. Then you look at how the data varies, the variable -- we call the factor you're testing
3:43
the independent variable and the result is the dependent variable. For instance, let's say you want to -- you notice plants in your neighbor's yards are growing faster than in your yard's. So you hypothesize that the fertilizer that your neighbor is using is better than the no fertilizer than you're using. So how do you prove that? You set up a controlled experiment. You
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set up identical groups, one you do not have fertilizer, that would be your control group. One you would have fertilizer, that would be your experimental group -- and then the growth of the plants would be the result or your dependent variable. So the control plants, without fertilizer. The experimental groups plants, with fertilizer. Fertilizer would be the independent variable and then the dependent variable is the growth rate (measured in cm). So
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hypothesis: "if I add fertilizer then my plants will grow faster." That's a simple hypothesis, obviously more complex experiments would have more complex hypotheses -- but you get the gist of it.
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Then you have to analyze that data clearly, measured and determine whether or not that supports your hypothesis. Analyzing data, you can observe. Your eyes will tell you whether the plants are growing faster, but you need to do more than that. You need to measure, so you'll record your observations. You'll record your measurements. Use the largest sample possible, that eliminates error (or reduces error, I should say) and then you will
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organize your data in a easy to follow way with graphics -- such as charts, tables or graphs.
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Conclusions -- then some conclusions are offered as models, some are inferences, but generally speaking a hypothesis that's been tested and tested many times and stands up to those tests is considered a theory.
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So that was the scientific method. Now we're going to move on to a little bit to the Natural History.
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We're looking at the ocean's Natural History, this is from the museum, The Smithsonian. So there's a large whale there the Natural History Museum.
6:45
About four billion years ago (3.5 -3.8 billion years ago) the universe came to be. Now we're not going to debate how this happened, because every culture has their story. We're going to look just at the scientific evidence that's there, so
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it's called "The Big Bang Theory." That was more of a joke because when it was first introduced, an explosion moving out, a "Big Bang." So it was kind of like a a poke-poke, ha-ha -- but it stuck.
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At the beginning, the beginning of the universe, we look at the beginning here -- and we're looking at pure energy. E = mc2. That links energy to matter, so as that energy is being released.
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Energy forms simple matter. Subatomic particles and then atoms. The first atoms would have been the simplest atom, Hydrogen. So the early universe - energy - subatomic - Hydrogen. These Hydrogen clouds we call nebula. Nebulae, they start to collapse in on themselves because of gravity. When critical mass is, when you reach critical mass you have Thermonuclear Fusion -- where Hydrogen fuses to Helium releasing
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large amounts of energy. Now that's what a star is -- so the early universe may have consisted of clouds of Hydrogen we call nebula, and they collapse on themselves forming the protostars, the earliest stars. Stars that interact with each other using gravity we call galaxies, and what's around that star solar systems. So the universe, according to the scientific evidence, is nearly 4 billion years old. It's expanding out in all directions, Hubble,
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Carl Hubble was an American astronomer who used the redshift to prove the universe is expanding.
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So widely accepted - energy to matter, this matter - nebula collapsed on themselves
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forming stars, so that's accepted. You'll never be able to prove it, it's a theory. We call that the Big Bang Theory, but it's still a theory that won't be ever proven.
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Like we mentioned, these nebula, and that's a famous nebula -- that pictures from the Hubble telescope named after Hubble, who used the redshift.
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That's called "The Pillars of Creation." Those are nebula, gas, hydrogen gas, forming stars. So that gravitational collapse -- is, that nebula is forming a star.
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So this image basically shows you your nebula -- followed by a protostar, an early primitive solar system sweeping out into planets. And then you have a developed solar system, we call that the “Sequence of formation.”
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So: Big bang - subatomic particles - hydrogen - nebula - solar system formations.
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So earlier, earlier we were allowed, what we were allowed -- yet we were able to put a date
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on these events using radioactivity, the decay of radioactive elements over time. This happens at a regular rate. It's like a clock an atomic clock. The oldest rocks we have found on Earth date back nearly 4 billion years -- 3.75 billion years. They're in the center of continents. Interestingly enough, the oldest ocean floor is about 225 million years -- far less, but we'll get into that when we talk about plate tectonics. So the oldest matter we found in the solar system is
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about 4.55 to 4.6 billion years old. We're looking at the age of the solar system and the age of the Earth would be about 4.6 billion -- so that time from 4.6 to 3.75 billion the Earth wouldn't be made of rocks, it would have been molten. It would have been cooling and various processes would have been occurring -- forming that Earth. So the solar system appears to be 4.5 or 4.6 billion years old
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and Earth being part of the solar system would be that same age, but the early Earth would have been far different from what we see today because it would have been cooling. Volcanoes out gas carbon dioxide, steam -- which eventually came oceans so the oceans, we believe were outgassed from these early volcanoes -- a lot of ammonia and methane according to the rock record. No oxygen according to the rock record. That would be introduced later by living things.
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This graph shows you the makeup of the atmosphere according to the rock record, and you can see about 2.5 billion years ago we have measurable oxygen -- but we see traces of oxygen all the way back to 3.5 billion years. These traces are near the earliest fossils and they're just bands of oxidized minerals. So, oxygen was gradually being introduced for about a billion years through photosynthesis until it became measurable and when it finally increased
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to a large enough percentage of the atmosphere multi-celled life was possible. Why oxygen? Well living things can survive without oxygen, very small things with anaerobic respiration -- but oxygen provides a lot more energy with aerobic respiration. 2 - 36
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ATP for anaerobic, 36 for aerobic, so that's significantly more ATP…which biological energy.
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So complex organisms need oxygen.
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So look -- complex organisms did not come into the fossil record until there was enough oxygen.
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The oceans – again, were likely formed from outgassing of these volcanoes as Earth cooled.
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The lithosphere would have formed, volcanoes outgassed water and hydrogen gas (which escapes because hydrogen's super light), nitrogen (which makes up the bulk of our atmosphere -- so as Earth stabilized these oceans formed.
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Earth would have cooled enough for this water to eventually stabilize because it probably would have evaporated and rained and evaporated and rained as the Earth was cooling. So oceans would have taken some time to form and then they would have collected in the basins.
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Comets would have delivered some (water). These planets, as they are sweeping out their orbits they're collecting material. The process is called accretion,
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so they're collecting this material and it certainly would have provided some oxygen.
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Astronomers believe (and scientists actually believe) that we hit a very large metal asteroid early in our formation -- which would have formed the moon because that crash would have shot debris into the air, and it gives us an extra-large metal core which has allowed for Earth's magnetic field and plate tectonics to continue far longer than Mars and Venus (our closest neighbors). That electric field around us or magnetic field,
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I should say, helps block solar wind and makes Earth a very habitable planet.
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The first life though -- are these blue-green bacteria, cyanobacteria. When I was in college we called them blue-green algae, they're still alive today -- we've talked about them on our field trips and here's the early filamentous blue-green bacteria. This is a 3.5 billion year old fossil an image of it and then the artist's rendition. So life has been around longer than 3.5 billion years. These fossils we call stromatolites. Ancient stromatolites. You can see this cross
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section are banded with oxidation, that's how we know they produced oxygen -- the earliest oxygen came from this blue-green bacteria reef we call a stromatolite. So these are the oldest
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organisms in the fossil record. They live in the ocean, the water would have protected them from UV light because the ozone layer that protects us now wouldn't have existed. Ozone is made from oxygen, so these prokaryotic (no nucleus) bacterial cells were the first evidence of life we have -- they are about 3.5 billion years old. The oldest ones and they were the only things that lived on our planet for nearly 2 billion years…
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…radiating oxygen into the atmosphere.
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These ocean basins -- now we're going to look a little bit about the ocean basins,
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this image is from The Mississippi. The Delta. A Delta is a common coastal formation where sediment is deposited into the ocean. This is an area where we have a dead zone -- the nutrients that wash, pour into the Gulf. The nutrient pollution we call eutrophication.
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So we'll look at the coast -- coastline is where the land joins the ocean. They're very Dynamic, which means they change. Here on our Coast we're studying these barrier islands, that we've looked at and the passes between the barrier islands -- like at Fort Desoto or Hurricane Pass at Honeymoon Island… They were formed by storms, so storms helped shape the coastline. Erosion and weathering help shape the coastline. Sea level rise (which we are
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currently rising now) helps shape the coastline. So all these phenomena change our coastline --
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now at the end of the last ice age (which ended about 18 000 years ago), the glacier’s melt poured into the ocean. Ocean, sea level rose about 400 feet -- that's when our barrier islands were formed…and we study the barrier islands in class. Like I said, Fort Desoto, Honeymoon Island -- all these beaches are barrier islands and they are between 18 000 and maybe 15-14 000 years old and they formed when sea level rose and that's deposition.
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This image would show you the Florida platform, which really is three times larger than the State of Florida. So that would have been exposed when the glaciers were all the way
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down into the United States -- as sea level Rose we have our current coastline. We've been stable for 10-12,000 years. If the remaining ice caps were to melt you would get something like the lower image, where much more of our coastline would disappear. Will that happen eventually? Of course, sea level rises and falls cyclically, as our ice caps grow and recede.
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The worry is with human accelerated climate changes -- we will make it happen sooner than we can adapt (and other organisms can adapt) because this is a slow process under normal circumstances. When something sudden happens, you can have a mass extinction. Mass extinctions -- we've had five in the history of life, are sudden changes that wipe out a large segment of life.
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This is a glorified image of the coastline. You can see that's how barrier islands form. What we study -- these barrier islands are huge sand bars that were formed at the end of the last ice age. So we have that up and down the Eastern Seaboard the Gulf Coast. These particular
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landforms -- look at that sand spit in that image, that's Fort Desoto…a large sand spit.
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Barrier islands, like Honeymoon, those islands are where our beaches are on the Gulf side and our mangroves are on the Intracoastal side (which is toward the continent).
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Then you, in those intracoastals between the Barrier Island the continent, you get seagrass beds. So this is much like our coast -- this is called a depositional coastline.
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Ocean sediments -- now the ocean floors covered with sediments. Our beaches are sand, and then when you go a little further out there's silt and clay. Those are land-based sediments -- you're also covered with fossil sediments from plankton that die. This image here is an electron microscope of a algae called coccolithophore, they bloom and when they die they sink and they form ooze. Ooze is unconsolidated plankton skeletons, that's ooze.
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So, our sediments can be organic – (but there’s) more inorganic.
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Oozes are organic sediments, and we did the microorganism lab or (we will, depending on when you're watching this video) we're going to learn about the calcium-based plankton and the silica-based plankton. When they die, they collect on the ocean floor and form deposits we call ooze.
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Inorganic sediments would be the sand and silt and clay washed from the continents.
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So, Terrigenous means from Earth, that's the sand, silt and clay from the continents. They’re the most abundant, but they don't cover the largest area -- but they are the most abundant because they're thick depositional structures. Biogenous are the oozes that come from our plankton and they dust the ocean wherever plankton live. Hydrogenous formed deep in the ocean in a lot of cases. Cosmogenous come from outer space.
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Terrigenous, you can see the two images -- there's erosion, washing sediments from land depositing them in the water supply -- or glaciers, scraping the land off, (They) break off as huge icebergs and deposit sediment. So those two processes bring terrigenous sediments into the ocean.
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Biogenous sediments are these organic, formed from living things. Calcium or silica based
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oozes. The image of foraminifera, in lab. Again, whether you've done it yet or will do it that's – Globigerina, it is a type of foraminifera that has calcium-based shells and they build up to form chalk limestones-- the Great Cliffs of Dover (England) -- those great chalk white cliffs are made of ooze.
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Another thing that oceanographers study are waves -- and one particular wave, the tides. They are very important to marine life, especially tidal flow. Organisms reproduce on the tides
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and strong tides would move these plankton around. A weak tide would not move the plankton around -- so reproduction is timed on the strongest tides, which happen on full and new moons. We'll get to that in a moment, but all a wave is -- is energy moving through a medium.
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This energy pulse causes a wave and you can see there's no net movement -- our friend the seagull there takes an orbital pattern but in the end is in the same place
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as he was when the pulse was approaching. So they're orbital patterns, but there's no net movement and it's how energy is moving through the water.
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The height of that wave is the crest or the trough (would be the negative height below the resting baseline) -- so crest and trough are the high points and low points -- the amplitude is the distance the crest and trough is from the baseline,
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so you can have a positive or negative amplitude (crest to baseline or trough to baseline).
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The wavelength is the distance between two waves. We generally talk about frequency more, how many waves pass per second – okay, so a long wavelength would be distance between the waves…
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…across crest to crest or trough to trough. High frequency would be many waves passing by
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in a short period of time, low frequency less waves. Notice this image -- the low frequency waves have a longer wavelength, the high frequency waves have a shorter wavelength,
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and in this image they have a similar amplitude...but high frequency = many waves passing by. Low frequency = fewer waves passing by.
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The three types of waves we look at are wind waves, wind waves, that's the most common.
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Then we have tsunamis which are the seismic sea waves.
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You also have storm surge -- which is not a complete wave but it's just a dome under a low pressure system, so it's half a wave…and then the third type of waves are from the tides. Now the period is how long it takes a wave to pass, so the period of a wind wave can be anywhere from less than a second waves pass to a second to 30 seconds. They're what we generally have on shore here. They come in, they roll, they come, in they
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roll --- and the Gulf side (because the Gulf is shallow) they're not huge. On the Atlantic side, because it's deeper, they get higher amplitudes -- but we're still not as deep as the Pacific Ocean where you have huge amplitude waves. The storm surge here in the Gulf, were concerned with is the dome of water underneath that low pressure storm as it moves ashore -- so it's half a wave… and then the seismic sea wave, the tsunamis. We don't get here, we're too shallow for it,
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but those waves had come by you'll get one and that would be five to ten minutes later you get another -- so they have a different frequency in period. Then the two types of tidal waves -- caused by the tide would be the diurnal (would be one wave per day, 24-hour period). Well, 24 hour and 50-minute period -- and then the semi-diurnal which would be two waves per day so that would be a 12 hour and 25 minute period. So the three types of waves are wind,
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seismic sea wave (tsunami) and tides -- and then we have a storm surge (which is half a wave). Those are where waves come from -- so wind, tides, seismic events and then we can put a half a wave in there with the storm surge. Now as waves and when waves are over deep water they travel undisturbed -- when they enter shallow water the lead wave slows down because it interacts with the bottom and the waves crowd the back waves catch up and then they spill over. So
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the height increases the wavelength gets shorter and then they spill -- they spill. It's called a breaker, and that happens in the surf zone. You go to the beach when you see the waves spill
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we call that breaking where they spill or break that is the surf zone. The surf zone usually carves out a little notch, so sand bars occur behind the surf zone and you have a little trough where the waves/surf, where the waves are. So that's typically how waves work. The longer the wavelength the higher the height increase. So, these tsunamis can have 10 mile wavelength and then when they reach shallower water they can have a hundred foot wave crest --
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here in the shallow water we don't get large waves like that, we get smaller waves.
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Shoaling occurs when the waves break offshore due to a sandbar or any other underwater obstruction.
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There's a picture of the storm surge -- the low pressure system pulls up a dome of water. That dome of water can be several feet high causing coastal flooding, but it's only one part of a wave
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and like I said organisms reproduce on the tides. Tides are caused by the gravity of the Sun and the Moon (mainly the Moon). We have two tidal bulges on Earth at one time, a gravitational and an inertial tide. This image is in France it's Mont Saint-Michel and you can see it's a peninsula at low tide and an island at high tide. It’s a famous tourist area because the tidal surges are so great that it's a unique environment,
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but there's our two title bulges – “A” would be the gravitational tide and then “C” would be the inertial tide -- so gravity and inertia are the two forces that cause tides.
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Semi-diurnal tides occur twice a day. Diurnal tides occur once a day. Mixed tides are usually semi-diurnal but tend to break down during the new moon cycle and they are of different heights. Here on the West Coast of Florida we get mixed tides, so our tidal cycle is mixed.
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Okay, this shows you from the side. This is a mixed tide, different heights.
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Okay…there's a high tide, but it's only in this case five feet, and then here's the second high tide and that's nearly nine feet. The low tides are of different heights as well, so this happens two times a day -- that is a mixed tide toward the new moon phase, when we have what we call a neap tide. We'll learn that one in a second. This cycle tends to break down a little bit, but you can see there here's us, red. Red would be mixed tide. All these places on Earth get the
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mixed tied. A diurnal tide is one high one low every day, one high one low -- simple tide. Okay, the east coast of the Gulf and these areas have diurnal tides. The most common is one high and one low of near equal heights, one high and one low of near equal heights -- so two waves per day…
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Of near equal heights. We call that semi-diurnal. Tt's not mixed semi-diurnal, and you can see the green areas on this map get the semi-diurnal tides.
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This is a tide table taken from Saint Pete, and look at here's a high tide (and we're about), there's the highest (where that little hatcher mark is). So a little less than three feet, and the low tide is a little below mean sea level. And then our next high is far more moderate, about one and a half feet, and our next low is moderate about one and a quarter feet…so you know, there's a low, two lows and two highs (in a) 24 hour period,
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but they're of different heights. That's mixed, that's our local tide.
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Now during a new moon and a full moon we have greater tidal swings that's called the spring tide. That's because the Sun the Earth and the Moon are on a straight line -- their gravities work together. So, notice here, spring tides have the highest tidal surge and the lowest tidal surge. Neap tides here less, shorter title surges. Here in the lower image you can see where the tides are breaking down in that mixed cycle, a little bit breaking down during neap.
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So during a full moon and a new moon you have spring tides, those are that greatest tidal swings. During the quarter moons you have neap tides, they're the least tidal swings. So water moves a lot during a full moon in a new moon, that's when organisms reproduce (and feed) the most. So if you're a fisherman the lunar cycle helps you target your fish. Reproduction occurs on these lunar cycles -- so organisms in the ocean reproduce on lunar cycles.
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Now spring and neap tides, like I mentioned, look at the top image. The Moon and the Sun -- all right angles to the Earth, so they have less tidal (less gravitational) influence. Where the spring tide’s the new moon and the full moon -- you have greater gravitational influence and larger tides. So that's the difference. So, with tides you need to know diurnal, semi-diurnal and mixed the patterns (the cycles), then you need to know spring and neap tides.
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Now coastal regions, especially these tide pools, get huge temperature swings. At low tide they're exposed to the Sun or the cold, and then that tide comes in and then the tide recedes -- so organisms that live there need to be able to handle temperature extremes. Need to handle being in different water chemistry, during low tide you have evaporation or rain diluting/concentrating your salinity. Those limpet, you can see right there, those
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are a type of snail that live in the intertidal zone. The intertidal zone is between the tides.
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They also reproduce on the tides, you can see the sperm being released by the sponges and the top, and then the lower coral releasing their eggs -- they do this on tidal cycles because the more water movement the more. The plankton move and the greater the mixing of the sperm the eggs from the different organisms.
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Salt marshes are unique and tide pools are unique habitats caused by tides -- and they get nutrients flushed in and flushed out by the tides. So, living things feed, reproduce and basically conduct their lives on tidal cycles. Their activities are influenced by the tides.
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Now large-scale water movements are ocean currents. We have wind belts on our planet, and they move - the trade winds and the westerlies move ocean water. These are important in our ocean regions, because remember, plankton ride these ocean currents. The image that you see there is of the Gulf Stream. That's the Gulf Stream. That is the strongest ocean current, it's a warm water current coming from the tropics, moving up the Eastern Seaboard
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and then out into the ocean. So that's -- hurricanes follow that Gulf Stream pattern, the trade winds give way to the westerlies following this pattern and ocean life moves using these large-scale geostrophic surface currents. Geostrophic means worldwide. Surface currents.
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So the two wind belts that move our water are the trade winds and the westerlies.
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Now this moderates world climate, keeps our ocean temperature habitable because the warm (water) is pushed up toward the poles and the cold (water) is pulled down toward the equator on these geostrophic currents. Weather and climate, nutrients are distributed throughout the ocean and of course animal migration patterns follow the currents. Tt's easier to swim with the current than against and plankton distribution is governed by these ocean currents.
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The Gyres -- you can see there every ocean has gyres. In each basin. So the North Atlantic has the North Atlantic Gyre consisting of the Gulf Stream, the North Atlantic current, the Canary current and the Equatorial current -- you can see that in the North Atlantic.
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These are geostrophic currents moving across the ocean.
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The southern hemisphere -- South Atlantic Gyre. North Pacific Gyre, South Pacific gyre even the Indian Ocean has a Gyre. We even have a small gyre in the Gulf called The Loop Current -- so that is driven by wind and steered by Earth's rotation.
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Something steered by the Earth's rotation is called the Coriolis Effect.
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So, ocean basins have gyres in them.
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The North Atlantic -- we call the North Atlantic (Gyre) the Sargasso Sea. A sea is a partially isolated body of water, so the Sargasso Sea is isolated by this geostrophic gyre and
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they're (gyres) over the deep ocean, so there's not much productivity deep water (in a gyre) over the deep ocean -- does not have a high primary productivity, not much life in there. Most life is toward the coasts or in the currents themselves, but that is the North Atlantic Gyre called the Sargasso Sea.
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Worldwide you can see all of these geostrophic gyres. Look at the Gulf of Mexico, that's the nice warm Loop Current. Incidentally, the east coast of every continent has warm water currents because of these gyres -- so mangroves tend to congregate on the east coast, sea grass beds, you have salt marshes above the freeze line. On the west coast of these continents (or up in the Arctic area), you generally have cooler current -- so you get more kelp forests and
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cold water habitats. Less coral reefs. More coral reefs in the eastern half of oceans,
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simply because of water temperature. Also, coastal climate is different because of these
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surface currents -- so take a minute to look at these surface currents and realize that there's very different environments on the west coast and east coast of continents because of these currents. Different weather patterns. Different storm surge patterns. Different life, different plankton habitats. Mangrove (on the) east coast of continents, in the tropical areas. Salt marshes north of that. On the west coast you get more kelp forest -- that's a cold water.
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So a very interesting dynamic here in the ocean. Take a look at the Peru Current down in South America and where it bends over and meets the South Equatorial Current -- there's a little bit of upwelling because the trade winds are moving it away from the coast. That is the most productive fishery in the world. When the trade winds slacken, which happens cyclically, that gyre stalls a little bit. We call that El Nino. So these ocean currents in conjunction with
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the winds really govern our plankton distribution, the distribution of marine life and world climate.
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Local currents -- A longshore current is when waves are coming in at a normal pattern. They're pushing down on the beach causing erosion. Longshore drift is what erosion is called by these currents. If you swim out and swim back you'll be able to tell what direction the longshore occurrence is because it'll move you a little bit. You might move a little bit to the east or a little bit to the west (or north, or south) depending on how your island
45:02
is oriented -- but that will longshore currents are in the direction of the prevailing winds.
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Now, rip currents are dangerous. They pull you out to sea and that is the return flow of water. So when your choppier weather with bigger waves have stronger rips, so when you get a storm in the Gulf you can have dangerous rip currents.
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Upwelling, like I mentioned, these are biological hot spots. When water is pushed to the surface, because deep water is nutrient rich and has plenty of oxygen, cooler water holds nutrients better, so this deep water which is cooler has a lot of nutrients in it. Upwelling areas are biological hot spots. Downwelling areas have very little life -- all right, they're very sterile because those nutrients are being driven deep.
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Now, like I mentioned before:
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The Gulf has its own loop in it -- The Loop Current. So that's the current that covers the Gulf. Now the weed-line, the weed-line – out, you know the loop current moves, moves through the Gulf and then we do have a weed-line. That's where the sea turtles live, in the weed-line. It's kind of cool, they run off the beach, swim out to the weed-line -- wherever the weed line is. (It) could
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be 50 miles, (it) could be 10 miles, (it) could be 100 miles. Obviously the further it is the greater the death rate of the baby sea turtles are, but then they get caught in this weed-line and they live on these floating weeds, moving around the loop current then out the Gulf Stream and around the ocean on these geostrophic currents -- and it takes a good 10 years for them to make the round
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trip across the Gulf Stream - North Atlantic - back down the Canary (current) - back into the equatorial. They could be 10-12 years old, living in these floating weed lines. When they make that return trip and they're a little bit bigger. Now they move back toward their natal beach and they're able to reproduce. So the whole life cycle of the sea turtles rely on these ocean currents. Well, that's all for our first video. I hope that you enjoyed it. I am looking forward to
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a great class as I know you are, I hope that you all have a fantastic rest of your day.
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