DJ Kast, Interview with Megan Switzer and the Basics of the CTD/ Rosette, May 28, 2015

NOAA Teacher at Sea
Dieuwertje “DJ” Kast
Aboard NOAA Ship Henry B. Bigelow
May 19 – June 3, 2015

Mission: Ecosystem Monitoring Survey
Geographical area of cruise:
Gulf of Maine
Date: May 28, 2015, Day 11 of Voyage

Interview with Student Megan Switzer

Chief Scientists Jerry Prezioso and graduate oceanography student Megan Switzer

Chief Scientist Jerry Prezioso and graduate oceanography student Megan Switzer

Megan Switzer is a Masters student at the University of Maine in Orono. She works in Dave Townsend’s lab in the oceanography department. Her research focuses on interannual nutrient dynamics in the Gulf of Maine. On this research cruise, she is collecting water samples from Gulf of Maine, as well as from Georges Bank, Southern New England (SNE), and the Mid Atlantic Bight (MAB). She is examining the relationship between dissolved nutrients (like nitrate and silicate) and phytoplankton blooms. This is Megan’s first research cruise!

In the generic ocean food chain, phytoplankton are the primary producers because they photosynthesize. They equate to plants on land. Zooplankton are the primary consumers because they eat the phytoplankton. There are so many of both kinds in the ocean. Megan is focusing on a particular phytoplankton called a diatom; it is the most common type of phytoplankton found in our oceans and is estimated to contribute up to 45% of the total oceanic primary production (Yool & Tyrrel 2003). Diatoms are unicellular for the most part, and a unique feature of diatom cells is that they are enclosed within a cell wall made of silica called a frustule.

Diatom Frustules. Photo by: 3-diatom-assortment-sems-steve-gschmeissner

Diatom Frustules. Photo by: Steve Schmeissner

Diatoms! PHOTO BY:

Diatoms! Photo by: Micrographia

The frustules are almost bilaterally symmetrical which is why they are called di (2)-atoms. Diatoms are microscopic and they are approximately 2 microns to about 500 microns (0.5 mm) in length, or about the width of a human hair. The most common species of diatoms are: Pseudonitzchia, Chaetocerous, Rhizosolenia, Thalassiosira, Coschinodiscus and Navicula.

Pseudonitzchia. Photo by National Ocean Service

Pseudonitzchia. Photo by National Ocean Service

Thalassiosira. Photo by: Department of Energy Joint Genome Institute

Thalassiosira. Photo by: Department of Energy Joint Genome Institute

Photo of Coscinodiscus by:

Photo of Coscinodiscus

Diatoms also have ranges and tolerances for environmental variables, including nutrient concentration, suspended sediment, and flow regime.  As a result, diatoms are used extensively in environmental assessment and monitoring. Furthermore, because the silica cell walls are inorganic substances that take a long time to dissolve, diatoms in marine and lake sediments can be used to interpret conditions in the past.

In the Gulf of Maine, the seafloor sediment is constantly being re-suspended by tidal currents, bottom trawling, and storm events, and throughout most of the region there is a layer of re-suspended sediment at the bottom called the Bottom Nepheloid Layer. This layer is approximately 5-30 meters thick, and this can be identified with light attenuation and turbidity data. Megan uses a transmissometer, which is an instrument that tells her how clear the water is by measuring how much light can pass through it. Light attenuation, or the degree to which a beam of light is absorbed by stuff in the water, sharply increases within the bottom nepheloid layer since there are a lot more particles there to block the path of the light. She also takes a water sample from the Benthic Nepheloid Layer to take back to the lab.

Marine Silica Cycle by Sarmiento and Gruber 2006

Marine Silica Cycle by Sarmiento and Gruber 2006

Megan also uses a fluorometer to measure the turbidity at various depths. Turbidity is a measure of how cloudy the water is. The water gets cloudy when sediment gets stirred up into it. A fluorometer measures the degree to which light is reflected and scattered by suspended particles in the water. Taken together, the data from the fluorometer and the transmissometer will help Megan determine the amount of suspended particulate material at each station. She also takes a water sample from the Benthic Nepheloid layer to take back to the lab. There, she can analyze the suspended particles and determine how many of them are made out of the silica based frustules of sinking diatoms.

 This instrument is a Fluorometer and is used to measure the turbidity at various depths. Photo by: DJ Kast

This instrument is a Fluorometer and is used to measure the turbidity at various depths. Photo by: DJ Kast

She collects water at depth on each of the CTD/ Rosette casts.

Rosette with the 12 Niskin Bottles and the CTD. Photo by DJ Kast

Rosette with the 12 Niskin Bottles and the CTD. Photo by DJ Kast

Rosette with the 12 Niskin Bottles and the CTD. Photo by DJ Kast

Rosette with the 12 Niskin Bottles and the CTD. Photo by DJ Kast

Up close shot of the water sampling. Photo by DJ Kast

Up close shot of the water sampling. Photo by DJ Kast

CTD, Rosette, and Niskin Bottle basics.

The CTD or (conductivity, temperature, and depth) is an instrument that contains a cluster of sensors, which measure conductivity, temperature, and pressure/ depth.

Here is a video of a CTD being retrieved.

Depth measurements are derived from measurement of hydrostatic pressure, and salinity is measured from electrical conductivity. Sensors are arranged inside a metal housing, the metal used for the housing determining the depth to which the CTD can be lowered. Other sensors may be added to the cluster, including some that measure chemical or biological parameters, such as dissolved oxygen and chlorophyll fluorescence. Chlorophyll fluorescence measures how many microscopic photosynthetic organisms (phytoplankton) are in the water. The most commonly used water sampler is known as a rosette. It is a framework with 12 to 36 sampling Niskin bottles (typically ranging from 1.7- to 30-liter capacity) clustered around a central cylinder, where a CTD or other sensor package can be attached. The Niskin bottle is actually a tube, which is usually plastic to minimize contamination of the sample, and open to the water at both ends. It has a vent knob that can be opened to drain the water sample from a spigot on the bottom of the tube to remove the water sample. The scientists all rinse their bottles three times and wear nitrile or nitrogen free gloves to prevent contamination to the samples.

On NOAA ship Henry B. Bigelow the rosette is deployed  from the starboard deck, from a section called the side sampling station of this research vessel.

The instrument is lowered into the water with a winch operated by either Adrian (Chief Boatswain- in charge of deck department) or John (Lead Fishermen- second in command of deck department). When the CTD/Rosette is lowered into the water it is called the downcast and it will travel to a determined depth or to a few meters above the ocean floor. There is a conducting wire cable is attached to the CTD frame connecting the CTD to an on board computer in the dry lab, and it allows instantaneous uploading and real time visualization of the collected data on the computer screen.

 

CTD data on the computer screen. Photo by: DJ Kast

CTD data on the computer screen. Photo by: DJ Kast

The water column profile of the downcast is used to determine the depths at which the rosette will be stopped on its way back to the surface (the upcast) to collect the water samples using the attached bottles.

Niskin Bottles:

Messenger- The manual way to trigger the bottle is with a weight called a messenger. This is sent down a wire to a bottle at depth and hits a trigger button. The trigger is connected to two lanyards attached to caps on both ends of the bottle.  When the messenger hits the trigger, elastic tubing inside the bottle closes it at the specified depth.

Todd with the manually operated Niskin Bottle. Photo by: DJ Kast

Todd holding a messenger to trigger the manually operated Niskin Bottle. Photo by: DJ Kast

IMG_7209

Todd with the manually operated Niskin Bottle. Photo by: DJ Kast

Todd with the manually operated Niskin Bottle. Photo by: DJ Kast

Manual CTD fully cocked and ready to deploy. Photo by DJ Kast

Manual CTD fully cocked and ready to deploy. Photo by DJ Kast

Here is a video of how the manual niskin bottle closes: https://www.youtube.com/watch?v=qrqXWtbUc74

The other way to trigger Niskin bottles is electronically. The same mechanism is in place but an electronic signal is sent down the wire through insulated and conductive sea cables (to prevent salt from interfering with conductivity) to trigger the mechanism.

Here is a video of how it closes electronically: https://www.youtube.com/watch?v=YJF1QVe6AK8

Conductive Wire to CTD. Photo by DJ Kast

Conductive Wire to CTD. Photo by DJ Kast

Photo of the top of the CTD. Photo by DJ Kast

Photo of the top of the CTD showing the trigger mechanism in the center. Photo by DJ Kast

Top of the Niskin Bottles to show how the white wires are connected to the top.

Top of the Niskin Bottles shows how the lanyards are connected to the top. Photo by DJ Kast

The pin on the bottom is activated when an electronic signal is sent through the conductive sea cables. Photo by DJ Kast

The pin on the bottom is activated when an electronic signal is sent through the conductive sea cables. Photo by DJ Kast

Using the Niskin bottles, Megan collects water samples at various depths. She then filters water samples for her small bottles with a syringe and a filter and the filter takes out the phytoplankton, zooplankton and any particulate matter. She does this so that there is nothing living in the water sample, because if there is there will be respiration and it will change the nutrient content of the water sample.

Filtering out only the water using a syringe filter. Photo by DJ Kast

Filtering out only the water using a syringe filter. Photo by DJ Kast

Photo by: DJ Kast

Syringe with a filter on it. Photo by: DJ Kast

This is part of the reason why we freeze the sample in the -80 C fridge right after they have been processed so that bacteria decomposing can’t change the nutrient content either.

Diatoms dominate the spring phytoplankton bloom in the Gulf of Maine. They take up nitrate and silicate in roughly equal proportions, but both nutrients vary in concentrations from year to year. Silicate is almost always the limiting nutrient for diatom production in this region (Townsend et. al., 2010). Diatoms cannot grow without silicate, so when this nutrient is used up, diatom production comes to a halt. The deep offshore waters that supply the greatest source of dissolved nutrients to the Gulf of Maine are richer in nitrate than silicate, which means that silicate will be used up first by the diatoms with some nitrate left over. The amount of nitrate left over each year will affect the species composition of the other kinds of phytoplankton in the area (Townsend et. al., 2010).

The silica in the frustules of the diatom are hard to breakdown and consequently these structures are likely to sink out of the euphotic zone and down to the seafloor before dissolving. If they get buried on the seafloor, then the silicate is taken out of the system. If they dissolve, then the dissolved silicate here might be a source of silicate to new production if it fluxes back to the top of the water column where the phytoplankton grow.

Below are five images called depth slices. These indicate the silicate concentration (rainbow gradient) over a geographical area (Gulf of Maine) with depth (in meters) latitude and longitude on the x and y axis.

Depth slices of nitrate and silicate. Photo by: This is the type of data Megan is hoping to process from this cruise.

Depth slices of nitrate and silicate. Photo by:  GOMTOX at the University of Maine
This is the type of data Megan is hoping to process from this cruise.

Elizabeth Bullock: Day 5, December 15, 2011

NOAA Teacher at Sea
Elizabeth Bullock
Aboard R/V Walton Smith
December 11-15, 2011

Mission: South Florida Bimonthly Regional Survey
Geographical Area: South Florida Coast and Gulf of Mexico
Date: December 15, 2011

Weather Data from the Bridge
Time: 3:15pm
Air Temperature: 23.6 degrees C
Wind Speed: 15.8 knots
Relative Humidity: 56%

Science and Technology Log

Liz takes a water sample

Here I am taking a water sample from the CTD.

Let’s talk about the flurometer!  The flurometer is  a piece of equipment attached to the CTD which is being used on this cruise to measure the amount of chlorophyll (specifically chlorophyll_a) in the water being sampled.  It works by emitting different wavelengths of light into a water sample.  The phytoplankton in the sample absorb some of this light and reemit some of it.  The flurometer measures the fluorescence (or light that is emitted by the phytoplankton) and the computer attached to the CTD records the voltage of the fluorescence.

The flurometer can be used to measure other characteristics of water, but for this research cruise, we are measuring chlorophyll.  As you know, chlorophyll is an indicator of how much phytoplankton is in the water.  Phytoplankton makes up the base of the marine food web and it is an important indicator of the health of the surrounding ecosystem.

At the same time that our cruise is collecting this information, satellites are also examining these components of water quality.  The measurements taken by the scientific party can be compared to the measurements being taken by the satellite.  By making this comparison, the scientists can check their work.  They can also calibrate the satellite, constantly improving the data they receive.

Combined with all the other research I’ve written about in previous blogs, the scientists can make a comprehensive picture of the ecosystem with the flurometer.  They can ask: Is the water quality improving?  Degrading?  Are the organisms that live in this area thriving?  Suffering?

Nelson records data from the CTD

Nelson records data from the CTD.

Collecting data can help us make decisions about how better to protect our environment.  For example, this particular scientific party, led by Nelson Melo, was able to inform the government of Florida to allow more freshwater to flow into Florida Bay.  Nelson and his team observed extremely high salinity in Florida Bay, and they used the data they collected to inform policy makers.

Personal Log

Today is my last full day on the Walton Smith.  The week went by so fast!  I had an amazing time and I want to say thank you to the crew and scientific party on board.  They welcomed me and taught me so much in such a short time!

Thank you also to everyone who read my blog.  I hope you enjoyed catching a glimpse of science in action!

Answers to Poll Questions:

1)      In order to apply to the Teacher at Sea program, you must be currently employed, full-time, and employed in the same or similar capacity next year as

a. a K-12 teacher or administrator

b. a community college, college, or university teacher

c. a museum or aquarium educator

d. an adult education teacher

2)      The R/V Walton Smith holds 10,000 gallons of fuel.  By the way, the ship also holds 3,000 gallons of water (although the ship desalinates an additional 20-40 gallons of water an hour).

Kathleen Harrison: Shumagin Islands, July 9, 2011

NOAA Teacher at Sea
Kathleen Harrison
Aboard NOAA Ship  Oscar Dyson
July 4 — 22, 2011

Location:  Gulf of Alaska
Mission:  Walleye Pollock Survey
Date: July 9, 2011

Weather Data from the Bridge
True wind direction:  59.9°, True wind speed:  11.44 knots
Sea Temperature:  9°C
Air Temperature:  8.9°C
Air pressure:  1009.74 mb
Foggy with 1 mile visibility
Ship heading:  88°, ship speed:  11 knots

Science and Technology Log

The Shumagin Islands are a group of about 20 islands in the Gulf of Alaska, southwest of Kodiak Island.  They were named for Nikita Shumagin, a sailor on Vitus Bering’s Arctic voyage in 1741.  They are volcanic in origin, composed mostly of basalt.

Shumagin Islands

Bold and mountainous, the Shumagin Islands rise from the sea in the Gulf of Alaska.

Several islands even exhibit hexagonal basaltic columns.  There are about 1000 people who reside in the islands, mostly in the town of Sand Point, on Popof Island.  According to the United States Coast Pilot (a book published by NOAA with extensive descriptions about coastlines for ship navigation), the islands extend out 60 miles from the Alaskan Peninsula.  They are bold and mountainous.

hexagonal basalt

When this island formed, volcanic lava cooled into basalt hexagonal columns.

The shores are broken in many places by inlets that afford good anchorages.  The shores are rockbound close to.  Fishing stations and camps are scattered throughout the group, and good fishing banks are off the islands.  Fox and cattle raising are carried on to some extent.

long range view of SI, Alaskan Peninsula

Shumigan Islands to the left, snow covered peaks of Alaskan Peninsula in background. An amazing sight on a rare sunny day in the Gulf of Alaska.

Sea water quality is very important to the scientists on the Oscar Dyson.  So important, that it is monitored 24 hours a day.  This is called the Underway System.  The sea water comes through an intake valve on the keel of the bow, and is pumped up and aft to the chem lab.  There, it goes through 4 instruments:  the fluorometer, the dissolved Oxygen unit, the Thermosalinograph (TSG), and the ISUS (nitrate concentration).

The fluorometer measures the amount of chlorophyll and turbidity in the sea water once every second.  A light is passed through the water, and a sensor measures how much fluorescence (reflected light) the water has. The amount of chlorophyll is then calculated.  The measurement was 6.97 µg/L when I observed the instrument.  The amount of  phytoplankton in the water can be interpreted from the amount of chlorophyll.  Another sensor measures how much light passes through the water, which gives an indication of turbidity.  Twice a day, a sample of water is filtered, and the chlorophyll is removed.  The filter with the chlorophyll is preserved and sent to one of the NOAA labs on land for examination.

chem lab

Here are all of the water quality instruments, they are mounted to the wall in the chem lab. Each one has a separate line of sea water.

The next instrument that the water passes through will measure the amount of dissolved oxygen every 20 seconds.  Oxygen is important, because aquatic organisms take in oxygen for cellular respiration.  From plankton to white sharks, the method of underwater “breathing” varies, but the result is the same – oxygen into the body.  The oxygen in the water is produced by aquatic plants and phytoplankton as they do photosynthesis, and the amount directly affects how much aquatic life can be supported.

The TSG will measure temperature, and conductivity (how much electricity passes through) every second, and from these 2 measurements, salinity (how much salt is in the water) can be calculated.  The day that I observed the TSG temperature was 8.0°  C, and the salinity was 31.85 psu (practical salinity units).  Average sea water salinity is 35.  The intense study of melting sea ice and glaciers involves sea water temperature measurements all over the world.  A global data set can be accumulated and examined in order to understand changing temperature patterns.

instrument to measure

This instrument measures the amount of nitrate in the sea water. It is called the ISUS.

The last instrument measures nitrate concentration in the sea water every couple of minutes.  It is called ISUS, which stands for In Situ Ultraviolet Spectrophotometer.  Nitrate comes from organic waste material, and tends to be low at the surface, since the wastes normally sink to the bottom.  The normal value is .05 mg/L, at the surface, at 8°C.  Values within the range of 0.00 to 25 mg/L are acceptable, although anything above 5 is reason for concern.

All of the data from these instruments is fed into a ship’s computer, and displayed as a graph on a monitor.  The Survey Technician monitors the data, and the instruments, to make sure everything is working properly.

New Species Seen today:

Whale (unknown, but probably grey or humpback)

Horned Puffin

Dall’s Porpoise

Krill

Chum Salmon

Eulachon

monitor shows current data

The current water quality data is shown on this computer screen beside the instruments.

Personal Log

Living on a ship is quite different from living at home.  For one thing, every item on the ship is bolted, strapped, taped, or hooked to the bulkhead (wall), or deck (floor).  Most hatches (doors) have a hook behind them to keep them open(this reminds me of when I put hooks behind my doors at home to keep little children from slamming them and crushing fingers).  Some hatches (around ladderways (stairwells)) are magnetically controlled, and stay open most of the time.  They close automatically when there is a fire or abandon ship situation or drill.  Every drawer and cabinet door clicks shut and requires moving a latch or lever to open it.  For some cabinet doors that you want to stay open while you are working in the cabinet, there is a hook from the bulkhead to keep it open.

bracket holds copier

The copier machine is held in place by a 4 post bracket that is bolted to the floor.

On every desk is a cup holder, wider on the bottom than the top, designed to hold a regular glass or a cup of coffee.  If one of those is not handy, a roll of duct tape works well for a regular glass.  All shelves and counters have a lip on the front, and book shelves have an extra bar to hold the books in.  Trash cans and boxes are lashed to the bulkhead with an adjustable strap, and even the new copier machine has a special brace that is bolted to the deck to hold it in one place (I heard that the old copier fell over one time when there was a particularly huge wave).  There are lots of great pictures on the bulkheads of the Oscar Dyson, and each one is fastened to the bulkhead with at least 4 screws, or velcro.  There are hand rails everywhere – on the bulkhead in the passageway (hallway) (reminds me of Mom’s nursing home), and on the consoles of the bridge.

hallway hand rails

This view down the hall shows the hand rail. It comes in handy during rough weather.

Desk chairs can be secured by a bungee cord, and the chairs in the mess (dining room)  can be hooked to the deck.

Another thing that is different from home is the fact that the Oscar Dyson operates 24-7 (well, in my home, there could easily be someone awake any hour of the night, but the only thing they might operate is the TV). The lights in the passageways and mess are always on.  The acoustics and water quality equipment are always collecting data.  Different people work different shifts, so during any one hour, there is usually someone asleep.  Most staterooms have 2 people, and they will probably be on opposite shifts.  One might work 4 am to 4 pm, and the other would work 4 pm to 4 am.  That way, only one person is in the room at a time (there is not really room for more than one).  There is always someone on the bridge – at least the Officer of the Deck (OOD) – to monitor and steer the ship.  During the day, there is usually a look out as well.

binoculars on the bridge

These binoculars are used by the look out to scan the surrounding area for anything in the water - whales, boats, islands, kelp, or anything else in proximity to the ship.

His job is to, well, look out – look for floating items in the water, whales, rocks, and other ships (called contacts or targets).  This helps the OOD, because he or she can’t always keep their eyes on the horizon.

I have thoroughly enjoyed living on the Oscar Dyson (we have had calm seas so far), and talking with the NOAA staff and crew.  They are ordinary people, who have chosen an extraordinary life – aboard a ship.  It has challenges, but also great rewards – seeing the land from a different perspective, being up close to sea life, and forging close relationships with shipmates, as well as participating in the science that helps us understand the world’s oceans.