Amanda Dice: Ending Week 1 at Line 8, August 26, 2017

NOAA Teacher at Sea

Amanda Dice

Aboard Oscar Dyson

August 21 – September 2, 2017


Mission: Juvenile Pollock Fishery Survey

map cropped
Oscar Dyson moves across the Shelikof Straight to collect the Line 8 samples

Geographic area of cruise: Western Gulf of Alaska

Date: August 26, 2017

Weather Data: 13.2 C, cloudy with light rain

Latitude 57 36.6 N, Longitude 155 .008 N



Science and Technology Log

As part of this survey, the scientists onboard collect data from what is known as “Line 8”. This is a line of seven sampling stations, positioned only a few miles apart, near the southern opening of Shelikof Straight between Kodiak Island and the Alaskan Peninsula. Water samples are taken at different depths at each sampling station to measure several different properties of the water. This study is focused on profiling water temperature and salinity, and measuring the quantities of nutrients and phytoplankton in the water.

The CTD rosette is lowered into the water using a winch – as seen from above.

To collect this data, a conductivity and temperature at depth (CTD) instrument is lowered into the water. This instrument can take water samples at different depths, by using its eleven canisters, or Niskin bottles. The water collected in the Niskin bottles will be used to determine the nutrient quantities at each station. The rosette of Niskin bottles also has sensors on it that measure phytoplankton quantities, depth, temperature, and how conductive the water is. Scientists can use the readings from conductivity and temperature meters to determine the salinity of the water.

Each Niskin bottle has a stopper at the top and the bottom. The CTD goes into the water with both ends of each Niskin bottle in the open position. The CTD is then lowered to a determined depth, depending on how deep the water is at each station. There is a depth meter on the CTD that relays its position to computers on board the ship. The survey team communicates its position to the deck crew who operate the winch to raise and lower it.

Niskin bottles are lowered into the water with the stoppers at both ends open.

When the CTD is raised to the first sampling depth, the survey crew clicks a button on a monitor, which closes the stoppers on both ends of Niskin bottle #1, capturing a water sample inside. The CTD is then raised to the next sampling depth where Niskin bottle #2 is closed. This process continues until all the samples have been collected. A computer on board records the depth, conductivity and temperature of the water as the CTD changes position. A line appears across the graph of this data to show where each sample was taken. After the Niskin bottles on the CTD are filled, it is brought back onto the deck of the ship.

They let me take control of closing the Niskin bottles at the sampling depths!
CTD screen cropped
I used this screen to read the data coming back from the CTD and to hit the bottle to close each Niskin bottle. The purple horizontal lines on the graph on the right indicate where each one was closed.

Water is collected through a valve near the bottom of each Niskin bottle. A sample of water from each depth is placed in a labeled jar. This study is interested in measuring the quantity of nutrients in the water samples. To do this it is important to have samples without phytoplankton in them. Special syringes with filters are used to screen out any phytoplankton in the samples.

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Syringes with special filters to screen out phytoplankton are used to collect water samples from the Niskin bottles.

The “Line 8” stations have been sampled for nutrient, plankton, and physical water properties for many years. The data from the samples we collected will be added to the larger data set maintained by the Ecosystems and Fisheries-Oceanography Coordinated Investigations (Eco-FOCI), Seattle, Washington. This NOAA Program has data on how the marine ecosystem in this area has changed over the last few decades. When data spans a long time frame, like this study does, scientists can identify trends that might be related to the seasons and to inter-annual variation in ocean conditions. The samples continue to be collected because proper nutrient levels are important to maintaining healthy phytoplankton populations, which are the basis of most marine food webs.


Collecting water samples from a Niskin bottle.

Personal Log

As we travel from one station to the next, I have some time to talk with other members of the science team and the crew. I have really enjoyed learning about places all over the world by listening to people’s stories. Most people aboard this ship travel many times a year for their work or have lived in remote places to conduct their scientific studies. Their stories inspire me to keep exploring the planet and to always search for new things to learn!

Did you know?

Niskin bottles must be lowered into the water with both ends open to avoid getting an air bubble trapped inside of them. Pressure increases as depth under water increases. Niskin bottles are often lowered down below 150 meters, where the pressure can be intense. If an air bubble were to get trapped inside, the pressure at these depths would cause air bubble to expand so much that it might damage the Niskin bottle!

Jacob Tanenbaum, October 13, 2008

NOAA Teacher at Sea
Jacob Tanenbaum
Onboard NOAA Ship Henry Bigelow
October 5 – 16, 2008

Mission: Survey
Geographic Region: Northeast U.S.
Date: October 13, 2008

Old fashioned navigation
Old fashioned navigation

Science Log

Happy Columbus Day everyone, and, since were in Canada, Happy Thanksgiving. Yes, that’s right, Thanksgiving. Here in Canada, Thanksgiving is celebrated on the second Monday in October. So a special note to my son Nicky: Happy Canadian Thanksgiving!  Back to Columbus Day, though. Since that’s probably what your all talking about at home. In honor of Columbus Day, I thought I would try something interesting.

I made a replica of the instrument Columbus used to navigate his ship. It is called a Quadrant. Columbus would sight the North Star with his quadrant and measure its angle above the horizon. That angle is equal to your latitude. He used a quadrant to measure that angle.

A quadrant
A quadrant

This is what a quadrant looks like. You hold it up so you can see the star you want in your site. The weighted rope simply falls over the scale of numbers and indicates the angle. What instrument in math looks like this? Post your answers on the blog if you think you know. So did I beat the GPS? You will have to watch this video to find out.

Want to try sighting the North Star yourself? Here is how: Find the Big Dipper. Trace an imaginary line from the spoon up. The first bright star you come to is the North Star. Want to find our more about using the stars to find your way, or Celestial Navigation, click here.

We are fairly far out to sea right now. There is a point of land in Nova Scotia, Canada about 100 miles to our north, but most land is around 200 to our west. We are seeing a lot of off-shore birds like the Shearwaters pictured here. These little birds spend most of their lives in the open water feasting on fish. They come on shore only to breed, so landlubbers don’t see them very much. What a treat. They were part of a large flock that was foraging in the nets yesterday afternoon during a tow.


We also have a few land birds on board. They may have been blown out to sea by storms and have stopped on our ship for a rest. Several were eating what they could find out of the nets on deck yesterday. The nets on the Bigelow have 6 sensors, each reporting different variables, such as depth, the width of the net opening and the height of the opening back to the scientists on deck. One of the sensors stopped working and had to be replaced yesterday. Take a look at this video of how the repair was done.

The water temperature outside is changing. It is now much colder than it was. When we were further west, we were towards a warm current called the Gulf Stream that moves north along the east coast of the USA. The water was about 63 degrees. Now we are in a cold water current called the Labrador Current. This current brings water south from the Arctic along the Canadian coast and ends in the Gulf of Main. The water here is about 55 degrees or so. We are not seeing the dolphins anymore and some of the science crew thing the water temperature may be too cold for them. Take a look at this map of the water temperatures. Brighter colors are warmer in this picture. We have moved from the warmer greener colored water into the cooloer blue colored water. The red line represents our course.

Water temperature illustration
Water temperature illustration

WOS students who have not had a chance yet, should compare our ship to the one Columbus Sailed. Go back and look through the blog at the pictures of Snuggy and Zee in the different parts of our ship to help you. Post your answers on the blog. Finally, something very interesting came up in our nets today. We got this off the bottom in 1000 feet of water. It is wood. Clearly cut and shapped by a person and for a purpose. It appears to have been down there for a long time. How do you think it got there? Post your answers on the blog!

CLE students, try using these images of ships in the past as a story starter. Write me a short story about a trip on an old sailing vessel and incorporate some of what you have learned about their technology in your story. Can you tell me the story of how that wood ended up on the bottom of the ocean? Please don’t post these to the blog. They will be too long. Print them and show them to me when I get back on land next week.


IMG_6782-766424And now some answers to your questions:

RM – Good question: A sea spider is a sea-creature related to the horseshoe crab. It just looks a lot like the spiders we see on land.

Have we seen any sharks? We have seen a lot of dog-fish, which are a type of shark, but are not very ferocious. Our captain saw a great white off the bridge. Unfortunately, I was working below decks at that moment and did not get out to see it in time.