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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!

Comments

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Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Angela - as you can see from the image of photosynthesis in this journal, diatoms require sunlight to photosynthesize. If diatoms are not in an area of sufficient light, they will not be able to produce food and will die. On 2016-09-14 18:32, PolarTREC wrote:
Gina Ash, Block B 's picture

Gina Ash, Block B said:

Are there a lot of the same types of diatom species in your location?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Gina - for each different species there can be many individuals. Remember, these diatoms are microscopic, so thousands or more can be found in a small amount of water. Even if there are 50 different species (I am just making up number as an example) in that water sample, that means there are more than 200 of each individual. On 2016-09-15 05:16, PolarTREC wrote:
Vivian Tran's picture

Vivian Tran said:

Hello Mrs. Pecarcik. Congratulations on your first incubation. I have a question about the diatoms' attaching to other marine environments. If some diatoms are able to attach to foating sea ice, are there any other diatoms that are able to attack to marine creatures to travel to different areas?
Cara Pekarcik's picture

Cara Pekarcik replied:

Alexa said: This is a good comment. I vaguely remember a study on diatoms on whales but I could be compeletly wrong, I miss Google..... On 2016-09-15 14:06, PolarTREC wrote:
Vivian Tran's picture

Vivian Tran said:

Hello Mrs. Pekarcik. Congratulations on your first incubation. I have a question about the diatoms' attaching to other marine environments. If some diatoms are able to attach to floating sea ice, are there any other diatoms that are able to attack to marine creatures to travel to different areas?
Cyrus X's picture

Cyrus X said:

What are some other types of phytoplankton.
Cyrus X's picture

Cyrus X said:

What are some other types of phytoplankton.
Cyrus X's picture

Cyrus X said:

What are some other types of phytoplankton.
Cara Pekarcik's picture

Cara Pekarcik replied:

Diatoms are the most common, however there are other types include cyanobacteria and dynoflagellates. Other types of bacteria are also included as types of phytoplankton. On 2016-09-15 15:56, PolarTREC wrote:
Steven L, Block B's picture

Steven L, Block B said:

What kind of clothing do you wear, from top to bottom? Do you wear a special type of mask or goggles?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Steven - you can see more about the ECW (Extreme Cold Weather) gear in a few of my previous posts. We also wear thermal layers, wool socks and other cold-weather gear. Many of the folks aboard have face coverings and we were given goggles to bring on the research cruise. On 2016-09-15 18:08, PolarTREC wrote:
Katrina D, Block E's picture

Katrina D, Block E said:

If diatoms' left the photic zone, how long could they survive? Also, what are blooms and what do they benefit?
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Katrina - I am not sure that anyone has measured exactly how long a diatom would survive without light. The blooms that I mentioned are rapid growth phases. They benefit the entire food chain in the Southern Ocean because diatoms are the primary producers. On 2016-09-15 19:23, PolarTREC wrote:
Mia's picture

Mia said:

Hello! I was curious if you are all monitoring the concentrations of nitrates, phosphates, and silica and their relationships with the iron concentrations in the water. Additionally, if silica is a limiting nutrient, why do diatoms decide to use this nutrient in their frustule? Thank you!
Cara Pekarcik's picture

Cara Pekarcik replied:

Hi Mia - yes, the science team is monitoring all of the nutrients. They can relate them to the iron concentrations, but can also relate them to other sets of data to look for trends. Silica is called a limiting factor because the amount of silica in the water generally limits the presence of diatoms. Because diatoms use silica to make the frustules, they are not expected to be found in areas of low silica. Also, diatoms presence can eventually reduce the amount of silica in the water because they use it to make the frustules as they divide and grow. On 2016-09-18 12:34, PolarTREC wrote:
Morgan Murphy's picture

Morgan Murphy said:

Do you think you'll discover any new diatoms that have not been discovered before?
Cara Pekarcik's picture

Cara Pekarcik replied:

Morgan, there is always that possibility! It would be exciting! Many of the microscope work and FlowCam analysis will be done after the cruise is over, so we will have to wait to find out. On 2016-09-26 06:50, PolarTREC wrote:
De'Rajon S block g 's picture

De'Rajon S block g said:

Hey how are you doing i just have one question . What is the furthest down you all have searched for diatoms , are they normally close to the surface or are t6hey deeper in the water ?
Cara Pekarcik's picture

Cara Pekarcik replied:

As mentioned in the journal, diatoms require light and are normally not found below the area of the water that receives light (photic zone). This is usually down to about 200m/600ft. On 2016-09-26 06:56, PolarTREC wrote:
Jason W, B Block's picture

Jason W, B Block said:

How many different genera of diatoms are there in antartica?
Fairoz basha's picture

Fairoz basha said:

Mam it's good for me....I'm res arch schloar.my research interest in Marine diatom isolation and feed formulation.please I need a article to 18 s rdna isolation of Marine diatom.if you are possible please help my research......need also best primer design and methods