Monday, April 30, 2007

The Coriolis effect does not affect your toilet.

Take a good look at your planet.

Purdy, ain’t she? So blue. And green. And yellow. And green and yellow in such organized bands across the globe. Start from the equator and look northward. Green, then yellow, then green again. Start from the equator and look southward. Green, then yellow, then green again. Why so organized? I'll tell you, homes, it's all about atmospheric circulation!

We live on a spherical planet and as such the most bulgy part of the world gets the most heat. Air at the equator is warmed up by solar energy and starts to rise. Convection takes over at this point and that warm air travels poleward while cooler air at the poles descends towards the equator. Simple enough, but not only is our planet spherical it rotates as well. The rotation of our planet sets in motion a very sneaky character that we now have to consider – the Coriolis effect.

Sorry to be a party pooper but no, your toilet is not affected by Coriolis. The system of fluid mechanics that is in your toilet is much too small to be influenced by the spinning of a gargantuan planet. What it does do is influence movement of stuff on the LARGE scale. I’m talkin’ ocean circulation, atmospheric circulation, intercontinental ballistic missiles, and the like.

As our warm air at the equator rises it looses the capability to hold moisture (see “Mommy, why does it rain?”). That’s why the tropics are so rainy. That air rises, dumps out all its moisture, then heads north or south. On its way it gets deflected by the Coriolis effect. The Coriolis effect deflects things to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. You have to be careful with this deflection business because you’ve gotta think about it in the perspective of the air itself. Think of yourself moving along with the air. You’ll always veer right in the Northern Hemisphere and veer left in the Southern Hemisphere. A little hippy-dippy but the visualization helps in the long run.

At 30º N and 30º S the air hits a region of high pressure due to the “piling up” of more air that hasn’t moved its big butts outta the way on the journey towards the pole. The air starts to fall. It doesn’t have any moisture in it anymore so 30º N and 30º S get blasted with hot, dry air. This is why the world’s great deserts live at these latitudes. When the descending air gets lower in the atmosphere, some of it moves pole ward but some of it heads back towards the equator, creating the Trade Winds. The Trade Winds blow from East to West and in olden days came in handy for things like, yep you guessed it, trading! Hey, they were sailors, not wordsmiths.
The air that keeps heading for the poles gets deflected from the West to the East, so we get the Westerlies between 30ºN and 60º N (and 30º S and 60º S). Around 60º N and 60º S our pole ward traveling air has been sufficiently warmed enough and rises again, giving us a bit of rain at these latitudes. We see on the figure above that the Horse Latitudes and Doldrums are spots you don’t want to get stuck in with a sailboat because there's no wind. They’re called the Horse Latitudes because if you got stuck with your ship in these spots and you’ve gotta lighten your load to get moving, overboard go the horsies! I’m not kidding.
In this way, we develop the 3 atmospheric circulation cells.
* Equator to 30º = Hadley cell.
* 30º to 60º = Ferrell cell.
* 60º to Pole = polar cell.

I’ve drawn the above diagram more times than I care to remember. I drew it for the first time in my Intro to Oceanography class and I know I drew it at least once this semester. It is one of the few diagrams that has a special place in my heart, which is kinda pathetic but true none-the-less.

Figure citations.

Monday, April 23, 2007

Rocks for Jocks

Let's back it on up today and cover some basic info that you might be missing from your Science diet: Rocks. Don’t roll your eyes and say “boooorrring”, rocks are great. They tell very interesting…oh, who am I kidding. They ARE fucking boring, but I have to know about them none-the-less. My heart belongs to the sea so I’ve never found rocks to be particularly compelling. Some people do though. Those people are called petrologists and can be identified by their penchant for carrying around magnifying glasses and hammers. They are freaks for rocks but can be very informative and quite charming, especially on long car rides. They’ll tell you all about that road cut, or those hills in the background, or a particular metamorphic outcrop. My advice to you is to not let them drive unless you want to know more than you intended to know about the sedimentary layering of a ditch on the side of the road.

The thing about rocks is that there is a lot of nomenclature, lots of vocabulary to learn. Rocks "are aggregates of minerals" as the official definition goes. There are three categories for rocks: Igneous, Sedimentary, and Metamorphic.

Igneous: These rocks are the freshest of the bunch. They’re either made volcanically at the surface (EXTRUSIVE) or by the cooling of magma beneath the earths surface (INTRUSIVE). Rocks look A LOT different if they cool at the surface or cool inside the earth. Cooling inside the earth gives the rock time to develop big, purdy crystals. If you’re an igneous rock being fired out of a volcano, you don’t have much time to cool off before solidifying so your crystals are going to be itty-bitty.

Within the realm of igneous rocks, we’ve got the stuff that makes up our continental crust and the stuff that makes up our oceanic crust. The two look very very different. Oceanic crust is MAFIC which means it’s really rich in iron and so it’s black. Our favorite mafic rocks are Basalt and Gabbro. Continental crust is FELSIC and made up of lighter stuff like potassium, sodium, and silicon. Rocks with potassium are very cute and pink, so you’ll get a lot of white and pink in rocks like Granite and Rhyolite.

Sedimentary: sed. rox are made from the eroded bits and pieces of other rocks. They are made when sediments cement themselves together and are squeezed enough to form a new rock. They are identified by the size of the sediments that make them up. We’ve got fine grained stuff like Shale and Siltstone, moving into medium/sand sized stuff like Sandstone, and then to rocks that have big ole’ chunks in them like Breccia and Conglomerate. In the category of Sedimentary rocks are also evaporites like Halite (rock salt) and Gypsum (shit you use to make wall board).

Metamorphic: These rocks were igneous or sedimentary rocks at one time, but have been mooshed or buried long enough to metamorphose into a new kind of rock. We’ve got stuff like Gneiss, with it’s nice layering (that’s a geology joke for those who didn’t get it [fucking kill me now]). Gneiss can begin its life as Granite or a layered sedimentary rock. We’ve also got Slate, the stuff that chalkboards were once made out of. Slate is very black and very well layered. You squeeze the shit out of Slate and you’ll eventually get Schist – the rock responsible for the destruction of the St. Francis Dam (see “Damn Dam”). Let’s see, what else. Marble is a metamorphic rock, so that’s nice. No not Gneiss, nice. Awww, Gawd. I’m boring myself so I must be boring you. But now you know about rocks so, I guess that’s good?

Monday, April 16, 2007

Damn Dam

Dam failures are bad. Really bad. Really really bad. As a society, we depend on our engineers to do the dirty work for us so we don’t have to think about all the hazards around us. And believe you me, there are plenty of hazards to worry about.

The class I teach has been talking a lot about the St. Francis dam lately. It was a dam built in the 20s by our friend William Mulholland. Two years after its completion, the dam failed and sent a wall of water roaring thru Santa Clarita and on out to the Pacific Ocean. It is the 2nd greatest loss of life in California, the 1st being the 1906 San Francisco earthquake. The tragedy killed at least 600 people (which is not insignificant considering the population of the area at the time) and ruined the career of our buddy Billy M.

After completing his first engineering masterpiece, the LA Aqueduct, Mulholland set his sights on water storage rather than water transport. He wanted to construct a reservoir of fresh water that LA could tap into incase something happened with the Aqueduct system. After the 1906 earthquake, geologists traced the San Andreas down to the vicinity of LA and Mulholland knew that his aqueduct snaked over the fault a couple times. It didn’t help that farmers were sabotaging the LA Aqueduct because of the royal screwing over they had received when water was diverted from the Owens Valley. He took all these factors into consideration and decided that it would be best to have a reservoir that could meet LA’s water needs for as long as necessary to get the water flowing again. A reservoir would need a dam.Above is a colorized picture of the St. Francis dam as it was. It's ok for that water to be comming out the middle. That part of the dam is called a spillway and allows water to be released from the reservoir when necessary. The 200ft gravity dam was completed in 1926 and promptly filled with water from the Aqueduct system. Everybody was happy, especially ole’ Mulholland.

The dam was leaky to begin with. Throughout 1926 and 1927, the damkeepers were forever noticing little spots of water seeping through the concrete. Mulholland justified these leaks by saying “Poppycock! (or whatever other 1920’s guffaw you can think of) That’s only natural. The concrete is settling as the reservoir is filling behind it, no big deal”.

Early in 1928, lots of people began tapping Mulholland on the shoulder saying “Ummm, there’s a lot of water leaking through your dam. Are you sure we shouldn’ be worried?” Under the advisement of the damkeeper, Tony Harnischfeger, Mulholland marched up to the dam for a personal inspection during the daylight hours of March 12, 1928. He walked on it, tapped it, probably kicked it a couple times, perhaps jumped up and down on it, and declared it safe. End of story. Stop calling me Harnischfeger he probably thought. What a pussy-ass damkeeper I’ve hired.
Even though it’s a confusing name, we should remember Tony Harnischfeger for being of sound mind. He was right to be worried because at 11:57pm that very same night, the dam busted wide open. A volume of water equal to three times the flow of the Mississippi roared down the canyon. It obliterated everything in its path. The map above shows the path the flood took. It followed along the Santa Clara River (see below) all the way to the ocean. Bodies were found as far south as San Diego and even Tijuana.

The cause of the break was not shotty engineering, but unsound geology. One side of the dam was built on an old landslide. The rocks on that side are schistoseschist being a metamorphic rock that has well defined layers. Under a sufficent load and with proper lubrication, this stuff sloughs off along the planes of the layering. The other side of the dam was built on a rock that disintegrates when wet. It seems solid enough when it’s dry, but saturate it with water and what was sturdy rock crumbles to pieces.

This catastrophe left Mulholland a broken man. To his credit, he did take full responsibility for the dam failure. Subsequent trials and investigations acquitted him of any egregious wrong-doing. What WAS his fault was the poo-pooing of any advice given to him by geologists before building his dam. He died in 1935 at the age of 79.

So there you have it. The story of St. Francis dam. Heavy shit, huh? I'll spare you the "those who do not learn from the past are doomed to repeat it" banter. It's an incredibly interesting story and one that all Angelinos especially should know.

* St. Francis Dam - J. David Rodgers and Kevin James. Department of Geological Engineering. University of Missouri - Rolla
* Santa Clara River - Matthew Trump

Friday, April 13, 2007

Know your Germaniums!

I'm having a hard time thinking today so let's stick with a subject that I know backwards and forwards: Germanium Isotopes.

Joke’s on you! There’s hardly anything to know about germanium isotopes.


In addition to working on my Master’s Project with the silica and germanium in the North Pacific, I’m also partly working on a project to measure germanium isotopes. If you mention germanium isotopes to an Isotope Geochemist, take special note of the worried look in their eyes and congratulate yourself on stumping a very smart person. My advisor and I are pretty much developing the technique for measuring these little guys in seawater. Why, you ask? Why give a shit about an element with such a ridiculous name? Well, I’ll tell you.

Germanium is #32 on the periodic table of elements. It’s a metalloid meaning that its behavior exists somewhere between a metal and non-metal. The most abundant isotope of germanium is Ge74 with 32 protons, 32 neutrons. Other isotopes of interest are Ge70, Ge72, Ge73, and Ge74. There are also some weird radioactive species of germanium floating around, but I don’t worry much about those guys. These are the four isotopes that I measure when I use a mass spectrometer (which I don’t like using very much [see “Mass Spectrometry Blows”]).

We’ve talked a little bit before about fractionation. Isotopic fractionation means that something (evaporation, precipitation, biology, whatever) has fucked with the natural abundance of isotopes in your sample. In the case of oxygen, fractionation happens during evaporation and precipitation. The fatty Fatterton isotopes get left behind in the seawater during evaporation and they are the first to drop out of the clouds when it rains.

Biology does an amazing amount of fractionation. It’s a lot easier to move around light isotopes than it is to move around heavy isotopes. This might not seem like a big deal to you and me, I mean come on! What’s a few atomic mass units? But when you are a single celled critter, that shit adds up. Carbon, oxygen, sulfur, and iron are all things that biology needs, and since life is inherently lazy it will to the least amount of work to get what it wants.

Problems that arise when one attempts to measure germanium isotopes:

1.) The mass difference between the lightest (70) and heaviest (74) species of germanium is not much compared to the overall weight of germanium: 4 mass units out of 74, which is only about 5%.

2.) There isn’t much germanium in seawater. My advisor and I have developed a way to concentrate ~ 99% of the germanium in a 20L seawater sample into about 40 mL. If I told you how we do it, I’d have to kill you.

3.) You have to have a top of the line Mass Spectrometer. Expensive and fussy.

4.) You have to be able to convert your germanium concentrate to a gas and input the gas into the Bitchy Mass Spectrometer at a perfectly constant rate. Sounds easy, but this shit is sensitive. We’re talkin’ isotopes, people.

So that’s where we’re at. We’ve got our germanium concentrate. We’ve got friends with mass specs, we just need to fine tune the procedure a little bit and voila! Germanium Isotopes! The Big Butt here is “But will this information be useful?” I don’t know, probably not. Useful or not though, it's still uncharted isotope territory that should be explored by someone and that someone is me!

Wednesday, April 11, 2007

Dishonorable Discharge

The class I teach is learning all about rivers, floods, and groundwater this week. This subject is important to learn about, especially for folks living in Los Angeles. I don’t know if you’ve ever noticed, but it doesn’t exactly rain all that much in LA, which is good because people turn into Road Retards as soon as the pavement is wet. But it’s also bad in that we have a population of 14 million that is sustained on imported water.

As anybody who has seen Chinatown should know, Angelinos are big, fat, greedy water thieves. Back in early part of the century the LADWP and specifically chief engineer William Mulholland planned a fantastically devious way to reroute water from up north in order to provide water to the booming population in LA. People affiliated with the DWP started buying up land in the area of Owens Valley (see map) and before you know it, the LADWP owned a shit-load of land with precious precious water on it.

^ Area of Water Stealing ^

There are now two aqueducts that pilfer water from up North. The original built in 1913 runs about 220 miles and the other, completed in 1970 runs 137 miles.

^ Crazy-ass Aqueducts ^

You gotta hand it to Mulholland for being ballsy enough to make this insane plan a reality. Had I grown up in or around OwensValley AND been subjected to the vast wind storms created by the drying of the lake bed AND thereby developed severe respiratory problems because of all the particulates in the air AND had my family’s farm get fucked out of their water rights, then I would absolutely despise the man and probably all Angelinos. OwensValley is now as dry as a bone. Recently Mayor Villaraigosa made a big to-doo about rerouting water back into the OwensValley. You can read all about it here:

As most things Mayors do, this flashy production is merely a matter of publicity and won’t really do much to restore OwensValley to what it was at the turn of the century.

But our story gets better! Not only do we jack water from Northern California, we also reroute water from the Colorado River (see below). LA gets about half its water from the LA Aqueduct system and about 40% from the Colorado River and State Water Project, um, projects. Only about 10% of the water we use comes from groundwater and surface runoff.

By rerouting water for our own consumption, we’ve now fucked over Baja Mexico for their part of the Colorado River. Where there used to be lush estuaries and wetlands are now desiccant.

Fascinating stuff, huh? Who knew that water could be so scandalous.

So the next time you are taking a shower or drinking a cool glass from the tap (god forbid!) or participating in a wet tee-shirt contest, be mindful of where your water has come from. It has been on a long an arduous journey and deserves your respect.

Figure references:
CO Aqueduct: (Colorado River Aqueduct © 2004 Matthew Trump
LA Aqueduct:
OwensValley: Owens Valley © 2004 Matthew Trump

Monday, April 9, 2007

Mass Spectrometry blows

Mass Spectrometers are big, expensive machines that rarely work properly. I have yet to encounter an Isotope Geochemist who likes working with them. If you own a mass spectrometer, chances are good that you spend the bulk of your budget getting the damn thing fixed only to have it poop out on you at a critical time. They’re fussy bitches. For instance, one that we have here at USC requires that you NOT walk around it as it is measuring for fear of screwing up the sample intake. It’s like a $750,000 baby.

So how do these stupid pieces of crap work? Well, I’ll do the best I can to explain the principles of Mass Spectrometry. Some of it will be hand-wavy because I’m not so keen on it myself, but you’ll get the gist. As always, we’ll begin at the beginning and explain the principles that make this instrument necessary.

Think back to the 4th grade when you learned about the atom. The basic components of an atom are protons, neutrons, and electrons. We define an element by its number of protons, but elements can and do have isotopes. An isotope is an atom with the same number of protons, but a different number of neutrons. For example: we’ve got Hydrogen (number 1 on the periodic table of the elements) which has two isotopes – Deuterium and Tritium. The most abundant of the three is plain, ole’ Hydrogen with one proton and one electron. Just an itty-bitty bit of all the Hydrogen we know and love is Deuterium (about 0.002%). Deuterium has one proton, one neutron, and one electron. Tritium has one proton and two neutrons and is radioactive with a half live of about 12 years.

Atoms can have LOTS of isotopes. Most of them are extremely unstable and only exist in the lab. Below is the famous “Chart of the Nuclides”. You’ve got the number of neutrons on the x-axis and the number of protons on the y-axis. The blue line is showing you a one-to-one relationship (protons = neutrons). You can see that the cluster of stable isotopes falls below this line. That’s because it’s really really hard for heavy atoms to be stable. Once you start pilling on the neutrons, you’re atom wants to break apart.

Since isotopes of the same element have a different number of neutrons, they have different masses. A Mass Spectrometer will let you separate out your isotopes according to those mass differences. Why all the bother, you ask? See “Science Lesson #2: Wally Broeker” for more info on why you would want to know the isotopic composition of something in the first place. Little critters tend to take up the lighter isotope of an element first, be it Sulfur, Carbon, Iron, Oxygen, Silica, etc. This is called fractionation. It’s only by looking at the isotopes of something (like sediments, or pyrite, or shells, or seawater) that you’ll see how much fractionation has been going on. From there you can infer what the biology has been up to.

To illustrate what a Mass Spectrometer actually does, imagine yourself running on a track. Or walking (lazy-pants!). You and a friend are walking along with you on the inside of the track and your friend on the outside. The track is an oval, so once you two reach the turn your friend has to walk faster to keep up with you. If she doesn’t walk faster she'll fall behind because you are a mean friend and won’t wait for her. In principle, this is what happens in a Mass Spectrometer.

Looking at the picture above, our atoms start out all together in the front part of the Mass Spectrometer (1). Let’s skip describing this part because the front end of our Mass Spec can get complicated depending on what kind of instrument you’re using. Our isotopes are spit out and head down what’s called a “Flight Tube” (2). At this point, a big magnet built into the Mass Spec pushes our isotopes around depending on their weight. This has nothing to do with the charge on the atom because our atoms have been stripped of their electrons (ionized). The heavier isotopes are going to take a different trajectory than our lighter isotopes (3). Little detector “cups” record how many atoms came down that path (4). At the end, you know how many isotopes came into each cup and from there you can calculate the abundancies of each isotope in your sample.

So there you have it: the principles behind Mass Spectrometry. A simple premises that is gummed up by complicated machinery. If I was smart I’d quit this grad student shit and get a job as a Mass Spec mechanic because as long as their will be Mass Specs, there will be broken Mass Specs.

Friday, April 6, 2007

Trig? Oh NO! Metry.

Let's learn some Math today.

You’re thinking: Boooo! Math blows! Show me your tits!

I’ll admit that most of Math is tedious and frustrating, but some subjects within the realm of Math can actually be useful. Like Trigonometry.

I didn’t appreciate Trigonometry when I was learning it, but looking back on it now I have very fond memories of my days in Trig class. My friendship with Sine and Cosine and Tangent has stood…uuuhh, standed? withstood (?) the test of time. I remember this one time that Cosine got so black-out drunk and threw up in my car! I’ll warn you, folks, do NOT give that function Tequila. Good times.

This might be a stroll down memory lane for some of you, and for others it may seem like I’m taking you down a poorly lit back ally where you are going to get stabbed for your shoes. Don’t worry. If anyone stabs you and steals your shoes it’s going to be me. You have nothing to fear from Math. In fact, Math might help you in this situation because god knows I’ll turn on you at the drop of a hat.

We’ll begin by looking at our friend, the triangle. A right triangle always has one 90º angle and two acute angles (angles less than 90º). Right triangles are where we get all of our Trigonometric constituents from, like sine, cosine, and tangent. Other types of triangles are:

Equilateral: all angles equal 60 º, all sides the same length
Isosceles: two sides are the same length, 2 angles are equal
Obtuse: one angle is bigger than 90º
Acute: all angles are smaller than 90º

Back to the right triangle. So we’ve got one angle of 90º (indicated by that boxy thingy in the corner) and two others that are less than 90º. Let’s define one of those angles as theta (the “O” looking thing with the line through the middle). Let’s also give each side a name: Stalin, Churchill, and Roosevelt. You get to brush up on your history today too! sin θ = opposite / hypotenuse = Churchill / Roosevelt
cosin θ = adjacent / hypotenuse = Stalin / Roosevelt
tangent θ = sin θ / cosin θ = opposite / adjacent = Churchill / Stalin

If we take these functions and flip around what’s on top (the numerator) and what’s on bottom (the denominator) we can define 3 more functions: secant, cosecant and cotangent

secant θ = upside-down cosine = hypotenuse / adjacent = Roosevelt / Stalin
cosecant θ = upside-down sine = Roosevelt / Churchill
cotangent θ = upside-down tangent = Stalin / Roosevelt

From here, Trigonometry takes the ball and runs with it. You get into identities, Pythagorean theorems, Reduction Formulas, Double-Angle Formulas, Power-Reducing Formulas, and so much more. It’s hard to appreciate that such a vast subject can be built on such simple principles. Drink it in folks, it's a profound concept. Trigonometry is my friend, and it can be your friend too!

Wednesday, April 4, 2007

Mommy, why does it rain?

Good Question. Why does it rain? The answer isn’t obvious. Let’s talk a little bit about the fabulousness of water vapor.

It’s a stone cold fact that warmer air can hold more water than cooler air. Hence, the favorite complaint of Bingo loving, cookie baking, grandmothers everywhere “It’s not the heat, it’s the humidity!” The relationship between water vapor content (which can be quantified via vapor pressure) and temperature looks like this:

It’s not linear, it's exponential. Air with properties above the line are called “supersaturated”. Air with properties below the line are called “undersaturated”. This can lead to something interesting when you mix them. Say you’ve got two parcels of air with different properties. One parcel, A, has a lower temperature and water vapor content and the other parcel, B, is warmer and has a higher water vapor content. (see below) Now bring those parcels into contact, they mix and the mixing line looks like this:
Uh oh! Our mixing line lives in the supersaturated zone, so put your galoshes on because you’re getting rained on, buddy.

Another reason why we get rain is because air cools as it rises. When it cools it’s less capable of holding moisture so all the water gets dumped out. This happens in places with topographic highs like mountains. You’ll always have a rainy side of your mountain and a dry side because of this very mechanism.

Keeping with today’s theme of simple questions with not-so-simple answers: why does air cool when it rises? Let’s back up and think about US, as humans, scurrying around on the surface of our plant. We don’t think about it much, but we’re under a lot of pressure because of all that gas in the atmosphere on top of us. Gas does have mass (rhyme!), and when you’ve got miles and miles of it piled up from the Earth’s surface out into the far reaches of space, it can add some serious poundage to your daily life. Right now you are being subjected to 14.7 pounds per square inch of atmospheric pressure. Right. Now. And. Now. Still Now. It’s always there, homes. Nothing you can do about it.

Gas, however, can do something about it. As gas moves up into the atmosphere, it moves into regions of lower pressure. It can relax finally, and stretch out. It expands and when it does that it cools.

Maybe the opposite case will cement this idea in your mind: when you pump up your bike tire, what happens? The tire warms up a little because you are compressing the air inside it. This process is called adiabatic heating or cooling. Whenever a gas expands, it cools. Whenever it compresses, it warms up.

So the next time some asshole tells you that it’s raining because God is crying, tell him about vapor pressure, mixing lines, and adiabatic cooling. If this angers and confuses your Redneck friend, just follow whatever you say with “America Rules!” and you’ll be safe.

Monday, April 2, 2007

Die, Die, Diatoms My Darling

I have this fantasy that biologists and geologists all actually hate one another. This is so NOT the case, but wouldn’t it be hilarious if there was this deep-seeded hatred amongst the two science tribes? We could have knife fights á la “Beat It”, but instead of knifes it would be broken Erlenmeyer flasks. We could sabotage each others experiments. “DNA sequencing? How about ‘Bunsen Burner explosion in the face!’” Take that, nerd.

However funny this may be, I have to do some biology for my work as an oceanographer. The bulk of ocean chemistry depends on what is going on in the biological realm, so I have to keep track of a few species of sea-faring critters. The three I am most familiar with are Diatoms, Coccolithophores, and Forams. Today we’ll look at the wonderful world of the Diatom.

Diatoms are the guys I like the best because they are the main players in the Silica cycle. They are phytoplankton (plants) that have a siliceous shell encasing them called a frustule or test. The ones I deal with live in the photic zone, which tends to be the upper 100m of water depending on how murky your water is. Diatoms can grow CRAZY fast. The majority of the time they multiply vegetativly meaning that one diatom will break into two smaller diatoms. Individuals have the ability to make a new shell in 10-20 minutes! They’re big fans of regions with high nutrients like upwelling zones and the Southern Ocean. Wherever and whenever there is a high concentration of nutrients in the water, diatoms will hit hard and fast. They’ll zoom in and use up all the nutrients, creating what is referred to as a “bloom”, and then die off quickly when the nutrient supply has been drained.

It’s not totally obvious why a plant would want to grow a siliceous frustule. There are a few theories to explain why this might happen:

1.) To serve as a UV filter. UV light is super bad for you when you are a tiny phytoplankton.
2.) To act as armor to protect them from other critters that graze on them (this is probably the most likely explanation).
3.) To act as ballast so they can float up and down in the water column.
4.) Because they want to, motherfucker.

The majority (70-80%) of the silica that diatoms take up to make their frustules gets recycled in the surface waters. Some of it makes its way down into the seafloor where it gets deposited. People like me go out and collect seafloor sediments in interesting locations in order to find out how much silica has made it to the seafloor and what (if any) implications that may have to the water chemistry in the region.

Diatoms are one of the few living creatures that are ok in my book. Make a diatom YOUR friend today!

Douglas (2006) Biogenic Sediments: Carbonate and Silica
Photo credit: Dr. Neil Sullivan, University of Southern Calif.