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Cara Pekarcik's picture

Thanks for Waiting

We officially moved onto the RVIB Nathaniel B. Palmer one week ago and we have already sampled ocean water for our first incubation. You have been patient with me as I explained the use of the FlowCam, learned how to sample nutrients and walked you through the requirements for trace metal clean procedures and incubations. I have also told you about the rough seas, long hours and cold temperatures that go along with this type of oceanographic research. I would not be surprised if you have asked yourself why researchers go through these extensive steps and travel to these extreme conditions to study microscopic organisms. I think you have waited long enough to hear about the star of the show.

Guest Writer - Alexa Sterling

Alexa Sterling from the University of Rhode Island (who you have seen featured in previous journals) is going to tell you a little about diatoms.

Alexa Sterling boarding the RVIB PalmerAlexa Sterling prepares to board the RVIB Nathaniel B. Palmer. This is Alexas first research cruise.

Dynamic Diatoms

Diatoms are an important group within the marine plankton and they are found in all the world’s oceans. These microscopic organisms depend on photosynthesis for their source of nutrition, by converting carbon dioxide, water, and the sun’s energy into oxygen and food (stored energy).

Overview of photosynthesis and some required nutrientsThis slide shows an overview of the photosynthesis reaction used by diatoms and other types of phytoplankton to produce food.

Because of this, diatoms make up the base of the food web as primary producers. They play a similar role in the oceans as plants play on land by being a tasty meal for many animals. In the Southern Ocean, diatoms feed many animals ranging from tiny krill (small shrimp-like crustaceans) to huge filter-feeding whales, like minke and humpbacks. Even their oxygen production is important because they provide us every 5th breath we take!

Antarctic diatomsThis photo shows three individual diatoms of the same species. Notice how these three boxes look like 'glass houses'. This 'house' is called the silica frestule. Photo by David Honig, Courtesy of Amber Lancaster (PolarTREC 2012), Courtesy of ARCUS

Diatoms are a type of phytoplankton, or marine plankton that photosynthesize. Plankton drift along with the water currents as they are unable to actively swim. Diatoms have special adaptations that help control their water depth without having to swim. It is important for diatoms to be in the part of the ocean that receives sunlight (photic zone) in order to photosynthesize. When the conditions such as light, water temperature, and others are particularly good, diatoms can reproduce rapidly forming blooms.

Tiny Creatures

There are about 14,000 – 18,000 different species of diatoms alive in the ocean today! All are unicellular, meaning that they are only made of one cell. Everything they need to survive is provided within that one cell: chloroplasts for photosynthesis, stored food energy, structures for reproduction, protection from predators, etc. They range in size from 2 um (micron) to 2 mm. Read the caption below the ruler picture to learn more about the size of a micron.

Metric rulerA micron (micrometer) is a metric unit of length, but it is not possible to see on a metric ruler. To visualize a micron, imagine 1000 lines in between each milimeter (or small set of lines on the above ruler). The distance between each one of the 1000 lines represents 1 micron. Photo courtesy George Hoday public domain pictures.

We need microscopes to see individual diatoms, but we can see a brown-green tinge to our filtered water samples. This color is from pigments in their photosynthetic chloroplasts letting us know there are phytoplankton in the sample. As you can see from the pictures of diatoms below, they can look drastically different from one another, but there are similarities. For instance, all diatoms live in “glass houses". Their cell wall is made of silica which is called a frustule. It fits together like a Petri dish, with one half larger than the other. There are two main shapes of the frustule: centric and pennate. Centric diatoms are circular while pennate diatoms are boat-shaped. Can you see examples of these two shapes in the pictures below?

FlowCam image of Southern Ocean Diatoms 2Another screen shot showing more sizes and shapes of the Southern Ocean diatoms. The large diatoms just to the left of center shows how the silica frustules can extend away from the main part of the diatoms 'skeleton'.

FlowCam image of Southern Ocean Diatoms 1This image is a screen shot from the first run of the FlowCam using samples from the first incubation station. The various sizes and shapes of the individual diatoms are easy to see. Each photo represent a diatom magnified four times its normal size.

Their frustules can have interesting unique features, and diatoms have been compared to works of art. Frustules may have spines, ridges, setae (hair-like extensions), and pore (hole) patterns. These distinguishing features help us tell different species apart. They also serve as useful adaptations in the challenging ocean environment. Spines can help increase the diatom’s buoyancy helping it float in the photic zone and not sink. Setae are long hair-like extensions that make it difficult for predators with small mouths like krill to eat them. Can you find examples of these characteristics in the diatom pictures?

Diatoms may be individual solidary cells, but often they are found connected together living in colonies. Colonies are made of diatoms of the same species. Colony formation is another adaptation that prevents predation by making the cells too large for a krill to eat. Diatoms can also attach to other surfaces in their marine environment. For example in the Southern Ocean, there are sea-ice diatoms which attach themselves to floating sea ice using mucus they produce. Just like looking at the filtered sea water, we know they are attached to the sea ice by the brown-green color of their pigments. We will be collecting sea-ice diatoms during this cruise.

Microbiology Vocabulary

You may have noticed many bold vocabulary words in this journal. Keeps your eyes peeled for many more vocabulary words as we start to find out what the scientist are doing with all of these dynamic diatoms!

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Cara Pekarcik's picture

Cara Pekarcik replied:

Jessica - the diatoms can be different from each other just like birds, fish and bears can be different. Different species can form if events occur that cause genetic changes.
Makeiyah Dambreville's picture

Makeiyah Dambreville said:

when you say "Even their oxygen production is important because they provide us every 5th breath we take" how do they provide us with what we need?
Cara Pekarcik's picture

Cara Pekarcik replied:

As mentioned above, diatoms undergo photosynthesis. It's through this process they produce oxygen which is released into the air we breathe. Because diatoms are so abundant in the oceans, they produce a large portion of the oxygen in the air. On 2016-09-13 12:13, PolarTREC wrote:
Kevin C, Block B's picture

Kevin C, Block B said:

What is the maximum depth diatoms can survive in, and do the diatoms die really fast if they leave the photic zone?
Cara Pekarcik's picture

Cara Pekarcik replied:

Usually, the photic zone extends to about 200m/600ft. Diatoms would not survive long outside of the photic zone. Luckily, they are fairly buoyant and can stay near the sunlight closer to the surface. On 2016-09-13 12:45, PolarTREC wrote:
Tony Z, Block B's picture

Tony Z, Block B said:

Did you know each other before the trip or were you guys all strangers to each other?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Tony - the researchers are working collaboratively and have known each other for a while. Some of the undergraduate, graduate students and lab technicians are meeting for the first time. Take a look as some of my journals from May and June and July to find our more about meeting the researchers for the first time. On 2016-09-13 12:55, PolarTREC wrote:
Jessica A, Block F's picture

Jessica A, Block F said:

Why are some diatoms so different from each other?
Anastasia Z, Block B's picture

Anastasia Z, Block B said:

How are diatoms formed and how do diatoms multiply fast?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Anastasia - diatoms use the silica that naturally occurs in the ocean water to create their 'houses'. This is similar to how we use bricks or wood to build the structure of our houses. Diatoms can multiply quickly because they are small. They also have the ability to reproduce sexually and asexually, so they can reproduce fairly fast. On 2016-09-13 14:47, PolarTREC wrote:
Jake O, Block A's picture

Jake O, Block A said:

Could it be possible for diatoms to grow in the waters near New England?
Cara Pekarcik's picture

Cara Pekarcik replied:

Yes, as mentioned above diatoms are found in oceans across the globe. There are the same types of diatoms that are found in both New England waters and the Southern Ocean even! - Alexa On 2016-09-13 15:35, PolarTREC wrote:
Danny F, Block A's picture

Danny F, Block A said:

What is the lowest temperature you have encountered on your way to Antarctica and has it impacted your research?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Danny - we have experienced temperatures in the teens, but the wind chill puts us below zero. This area of Antarctica is a little milder than areas like the South Pole. So far, we haven't been impacted by the cold, but we have had to change plans for ice and rough seas. On 2016-09-13 15:37, PolarTREC wrote:
Jake O, Block A's picture

Jake O, Block A said:

I assume in the middle of the ocean there is absolutely NO internet. How do you post your journals to the internet if there is no internet?
Cara Pekarcik's picture

Cara Pekarcik replied:

Jake - this is such a great question! One of the ship's IT staff gave me a little tour of the ship's satellite Internet capabilities today. We actually have more of a connection than I expected. I send my journal's through email to the staff at PolarTREC and they format the journal for publishing. I found the process of sending emails off the ship to be pretty interesting, so I am actually going to write a journal on it when I have time. Keep checking back for an update. On 2016-09-13 15:40, PolarTREC wrote:
Britney B, Block B's picture

Britney B, Block B said:

Is there other types of diatoms other than the ones that attach themselves to sea ice and the ones that float on top of the surface?
Cara Pekarcik's picture

Cara Pekarcik replied:

Yes, diatoms can attach to many other surfaces in the marine environment such as seaweed. Most diatoms live floating in the ocean water. Diatoms are also found in freshwater water, some damp soils, and even in the air if there's moisture present in some cases! - Alexa On 2016-09-13 16:46, PolarTREC wrote:
Jenny T Block F 's picture

Jenny T Block F said:

Are these diatoms in the water equivalent to what a plant is on land?
Cara Pekarcik's picture

Cara Pekarcik replied:

As mentioned above, diatoms play the same role in the food web as plants play on land. They are both primary producers that undergo photosynthesis. - Alexa On 2016-09-13 17:24, PolarTREC wrote:
Lindsay lee's picture

Lindsay lee said:

Why are the diatoms such an Important part of Marine plankton
Cara Pekarcik's picture

Cara Pekarcik replied:

As mentioned earlier, diatoms are an important part of the marine plankton because they act as the base of the food web and produce oxygen we breathe. - Alexa On 2016-09-13 17:31, PolarTREC wrote:
Jeri Sever's picture

Jeri Sever said:

Cara, do you have to travel so far to do this study and does it have to be in cold water?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Jeri! Thanks for following along and for the question. Diatoms are found in both salt and fresh water all over the world. So, do we HAVE to travel this far and into such cold water? No. Do we WANT to travel this far and into such cold water? Yes. The scientists that I am fortunate enough to work with on this trip are specifically interested in Antarctic cold-water diatoms and iron interactions. Each have studied diatoms in other areas of the world, but this research trip is specific for this type of diatoms. On 2016-09-14 04:33, PolarTREC wrote:
James A's picture

James A said:

would any storm or change of water currents affect the incubation?
Cara Pekarcik's picture

Cara Pekarcik replied:

The incubation happens aboard the ship, so currents wouldn't affect the process. The rough seas could certainly make it more difficult to transfer samples. On 2016-09-14 08:21, PolarTREC wrote:
James A's picture

James A said:

would a change in water current change the amount of diatoms you collect?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi James - there may be different populations between distinct current patterns, but the currents shouldn't change the amount collected. Upwelling currents can actually help mix the water layers and initial the spring/summer bloom for the diatoms. On 2016-09-14 08:29, PolarTREC wrote:
Nha H, Block A's picture

Nha H, Block A said:

Are diatoms prone to drastic temperature changes?
Cara Pekarcik's picture

Cara Pekarcik replied:

As long as the water surrounding the diatoms does not change drastically, the diatoms will be ok On 2016-09-14 11:04, PolarTREC wrote:
Victoria H, Block G's picture

Victoria H, Block G said:

How will the diatoms get the sunlight
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Victoria - sunlight can pass through the water column to certain depth. This area of the water is called the photic zone and it's maximum depth is determined by the clarity or transparency of the water. It can be different for different part of the world. On 2016-09-14 11:31, PolarTREC wrote:
Maria Block F's picture

Maria Block F replied:

What happens if a diatom gets too close to the waters surface? If enough diatoms are together can it change the surface color of the water ( like when you have a collection of algae on your pool floor or walls.) Also what happens if a diatom gets too deep in the ocean. Is it possible for an ocean current to carry the diatom into waters that are too cold or too hot for the diatom to survive?
Cara Pekarcik's picture

Cara Pekarcik replied:

From Alexa: Too close to the surface where the sunlight is too strong - it may damage the diatom's ability to photosynthesize and/or kill it because of that. Yes, when diatoms bloom you can sometimes see a discoloration in the water. Sometimes in freshwater systems, enough diatoms blooming you can see a brown slippery layer they form. If a diatom gets too deep, it will not be able to receive sunlight, photosynethesize, and subsequently die. Yes, ocean currents can carry diatoms since they are drifting phytoplankton. Some diatoms can survive a range of temperatures, others cannot. On 2016-09-15 16:50, PolarTREC wrote:
Ryan G, Block F's picture

Ryan G, Block F said:

How long is it before the diatoms dies?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Ryan - you are not the first to ask this question. There isn't actually an answer to this question because scientists have not followed an individual diatom throughout its life span. It probably also depends on how the diatom is reproducing. Diatoms can reproduce sexually (two parents) or asexually (one cell dividing into two). If diatoms divide asexually, one of the offspring is smaller in size. Because there is always one offspring that decreases in size, one of the cells will eventually not be able to survive. On 2016-09-14 11:57, PolarTREC wrote:
Ryan G, Block F's picture

Ryan G, Block F said:

Do you catch different diatoms is different areas?
Cara Pekarcik's picture

Cara Pekarcik replied:

Ryan - if you look at the diatom photos from the FlowCam (they are included with this journal), you can see that there are many different types of diatoms in the images. These diatoms were all collected from the same sample area. On 2016-09-14 12:00, PolarTREC wrote:
Morgan Murphy's picture

Morgan Murphy said:

How do spines help diatom's buoyancy?
Cara Pekarcik's picture

Cara Pekarcik replied:

The spines help to increase the surface area of the diatoms to allow more buoyancy. -Alexa On 2016-09-14 13:06, PolarTREC wrote:
Melissa Z, Block A's picture

Melissa Z, Block A said:

Hi Ms. Pekarcik, Are there any other organisms that contain cell walls made of silica (frustules) besides Diatoms? If so, could you name some of them?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Melissa - Great question! Frustules appear to be specific to diatoms! On 2016-09-14 15:01, PolarTREC wrote:
Julia Brady, Block G's picture

Julia Brady, Block G said:

How long does it take for the diatom to die?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Julia - you are not the first to ask this question. There isn't actually an answer to this question because scientists have not followed an individual diatom throughout its life span. It probably also depends on how the diatom is reproducing. Diatoms can reproduce sexually (two parents) or asexually (one cell dividing into two). If diatoms divide asexually, one of the offspring is smaller in size. Because there is always one offspring that decreases in size, one of the cells will eventually not be able to survive. On 2016-09-14 16:12, PolarTREC wrote:
Jeffrey Diep's picture

Jeffrey Diep said:

Hello Mrs. Perkarcik, I was wondering why diatoms don't just die as they are always in constant freezing temperatures or is it because they are at a certain depth in the ocean so they don't freeze.
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Jeffrey - as Alexa explained, these diatoms are cold-water diatoms. They are adapted for life in cold temperatures. On 2016-09-14 17:49, PolarTREC wrote:
Anh D Block F's picture

Anh D Block F said:

How do diatoms produce oxygen?
Cara Pekarcik's picture

Cara Pekarcik replied:

Anh - Take a look at the image showing the chemical reaction for photosynthesis. The chemical reaction produces oxygen. This is just like plants. We will look at this more in class when I return in October. On 2016-09-14 17:56, PolarTREC wrote:
Anh D Block F's picture

Anh D Block F said:

How do diatoms produce oxygen?
Angela Y, Block F's picture

Angela Y, Block F said:

What will happen to the diatoms if they are not in areas part of the ocean that receive sufficient sunlight?