Ragupathy Kannan: Ocean Salinity to Ocean Sunfish, August 26, 2019

NOAA Teacher at Sea

Ragupathy Kannan

Aboard NOAA Ship Gordon Gunter

August 15-30, 2019

Mission: Summer Ecosystem Monitoring

Geographic Area of Cruise: Northeast U.S. Atlantic Ocean

Date: August 26, 2019

Weather Data from the Bridge

Latitude: 41.27688
Longitude: -67.03071
Water temperature: 18.4°C
Wind Speed: 14.8 knots
Wind Direction: 41°
Air temperature: 18.6°C
Atmospheric pressure: 1021 millibars
Sky: Cloudy

Science and Technology Log

We entered Canadian waters up north in the Gulf of Maine, and sure enough, the waters are cooler, the sea choppier, and the wind gustier than before.  And the organisms are beginning to show a difference too.  Our Chief Scientist Harvey Walsh showed me a much longer arrow worm (Chaetognatha) from the plankton samples than we had encountered before (see photo below).  And there are more krill (small planktonic crustaceans) now. 

arrow worm
We got this beautiful arrow worm in our plankton sample as we entered colder waters

So far in my blogs, I have focused on sampling of biological organisms like plankton.  But recall that in an ecosystem monitoring survey like ours, we need to measure the abiotic (non-biological) aspects too because the word Ecosystem covers a community of organisms along with their biotic and abiotic environment. 

In today’s blog, I will highlight the ways various important abiotic components are measured.  You will learn about the interdisciplinary nature of science.  (Feel free to pass this blog on to physics, chemistry, and engineering majors you know—it may open up some career paths they may not have explored!).  I will come back to biotic factors in my next blog (seabirds and marine mammals!).


The CTD is a device that measures Conductivity, Temperature, and Depth.  We lower a heavy contraption called a Rosette (named due to its shape, see photo below) into the water. It has bottles called Niskin bottles that can be activated from a computer to open at specific depths and collect water samples.  Water samples are collected from various depths.  Electrical conductivity measurements give an idea of salinity in the water, and that in turn with water temperature determines water density.  The density of water has important implications for ocean circulation and therefore global climate.  In addition, dissolved inorganic carbon (DIC) is also measured in labs later to give an idea of acidity across the depths.  The increased CO2 in the air in recent decades has in turn increased the ocean’s acidity to the point that many shelled organisms are not able to make healthy shells anymore.  (CO2 dissolves in water to form carbonic acid).  Addressing the issue of increasing ocean acidity and the resulting mass extinction of shell-building organisms has become a pressing subject of study.  See the photos below of CTD being deployed and the real-time data on salinity and temperature transmitted by the CTD during my voyage.

lowering the CTD
I assist lowering the CTD Rosette into the water. The gray cylinders are Niskin bottles that can be activated to open at various depths.
CTD data
This display shows the real time data from each scan the CTD sends back to the computer. The y-axis is depth in meters, with sea surface at the top. The instrument was sent down to 500 meters deep. The green lines show fluorescence, an estimate of phytoplankton production. Note that the phytoplankton are at the photic (top) zone where more light penetrates. The blue line shows water temperature in degrees Celsius and the red line shows salinity. (Photo courtesy: Harvey Walsh)


The ship is equipped with a highly sensitive sonar device called EK-80 that was designed to detect schools of fish in the water. (See photo of it attached to the hull of our ship, below).  It works by sending sound waves into the water.  They bounce off objects and return.  The device detects these echos and generates an image.  It also reflects off the sea bottom, thus giving the depth of the water.  See below an impressive image generated by our EK-80, provided kindly to me by our amicable Electronics Technician, Stephen.

EK-80 display
A remarkable screen shot of the EK-80 display of our ship passing over the Chesapeake Bay Bridge Tunnel as we headed out to sea from Norfolk, Virginia. To the left is a huge mound of dirt/rock, and just to the right of the mound, is a ravine and the tunnel (has a small peak and spikes). To the right (seaward side of the tunnel) you can see dredge material falling from the surface. We observed the sand and silt on the surface as we were passing through it. (Courtesy Stephen G. Allen).

The Acoustic Doppler Current Profiler (ADCP)

Scientists use this instrument to measure how fast water is moving across an entire water column. An ADCP is attached to the bottom of our ship (see photo below) to take constant current measurements as we move.  How does it work? The ADCP measures water currents with sound, using a principle of sound waves called the Doppler effect.  A sound wave has a higher frequency as it approaches you than when it moves away. You hear the Doppler effect in action when a car speeds past with a building of sound that fades when the car passes. The ADCP works by transmitting “pings” of sound at a constant frequency into the water. (The pings are inaudible to humans and marine mammals.) As the sound waves travel, they bounce off particles suspended in the moving water, and reflect back to the instrument. Due to the Doppler effect, sound waves bounced back from a particle moving away from the profiler have a slightly lowered frequency when they return. Particles moving toward the instrument send back higher frequency waves. The difference in frequency between the waves the profiler sends out and the waves it receives is called the Doppler shift. The instrument uses this shift to calculate how fast the particle and the water around it are moving. (From whoi.edu)

The University of Hawaii monitors ocean currents data from ADCPs mounted in various NOAA ships to understand global current patterns and their changes. 

hull of NOAA Ship Gordon Gunter
The hull (bottom surface) of the ship showing the EK-80 and ADCP systems, among other sensors. Photo taken at the ship yard. (Courtesy: Stephen G. Allen)


Hyperpro is short for Hyperspectral profiler, a device that ground truths what satellites in outer space are detecting in terms of light reflectivity from the ocean.  What reflects from the water indicates what’s in the water.  Human eyes see blue waters when there isn’t much colloidal (particulate) suspensions, green when there is algae, and brown when there is dirt suspended in the water.  But a hyperpro detects a lot more light wavelengths than the human eye can.  It also compares data from satellites with what’s locally measured while actually in the water, and therefore helps scientists calibrate the satellite data for accuracy and reliability.  After all, satellites process light that has traversed through layers of atmosphere in addition to the ocean, whereas the hyperpro is actually there. 

deploying hyperpro
A Hyperpro being deployed

Career Corner

Three enterprising undergraduate volunteers.

Volunteers get free room and board in the ship in addition to invaluable, potentially career–making experience.

undergraduate volunteers
David Caron (far side), Jessica Lindsay, and Jonathan Maurer having some much-needed down time on the flying bridge

David Bianco-Caron is doing his B.A. in Marine Science from Boston University (BU).  His undergraduate research project at the Finnerty Lab in BU involves a comb-jelly (Ctenophore) native to the West Atlantic but which has become an introduced exotic in the East Atlantic.  David studies a cnidarian parasite of the comb-jelly in an attempt to outline factors that could limit the comb-jelly.  The project has implications in possible biological control. 

Jessica Lindsay finishes a B.S. in Marine Biology later this year and plans to get her Small Vessels operating license next year.  This is her 2nd year volunteering in a NOAA ship.  She received a NOAA Hollings Scholarship which provides up to $9500 for two years (https://www.noaa.gov/office-education/hollings-scholarship).  It entailed 10 weeks of summer research in a lab.  She studies how ocean acidification affects shelf clams. 

Jonathan Maurer is a University of Maine senior working on a B.S. in Climate Science.  He studies stable isotopes of oxygen in ocean waters to understand ocean circulation.  The project has implications on how oceanic upwelling has been affected by climate change.  He intends to go to graduate school to study glaciers and ocean atmosphere interactions. 

See my previous blog for information on how to become a volunteer aboard a NOAA research ship.

I also had the pleasure of interviewing our Executive Officer (XO), LCDR Claire Surrey-Marsden.  Claire’s smiling face and friendly personality lights up the ship every day. 

XO Claire Surrey-Marsden
Our Executive Officer (XO), LCDR Claire Surrey-Marsden

Claire is a Lieutenant Commander in the NOAA Corps:

The NOAA Commissioned Officer Corps is made up of 321 professionals trained in engineering, earth sciences, oceanography, meteorology, fisheries science, and other related disciplines. Corps officers operate NOAA’s ships, fly aircraft, manage research projects, conduct diving operations, and serve in staff positions throughout NOAA. Learn more: https://www.omao.noaa.gov/learn/noaa-commissioned-officer-corps

Q. Thanks for your time, Claire. You’re the XO of this ship.  What exactly is your role?

A. The Executive Officer is basically the administrator on board.  We help with staffing, we manage all the crew, we have a million dollar budget for this ship every year that we have to manage.  Everything from food to charts to publications, all these get managed by one central budget. I’m kind of the paper work person on board.

Q. What’s your background?

A. I have a marine biology degree from Florida Tech. I’ve done marine mammal work most of my career. I joined NOAA in 2007, before that I was a biologist for Florida Fish and Wildlife [FFW].

Q. I heard you have done necropsies of marine mammals?

A. I was a manatee biologist for FFW for 3 years, we also dealt with lots of whales and dolphins that washed up on shore. I’ve also done marine mammal work in my NOAA career.  Worked with Southwest Fisheries Science Center on Grey Whales and dolphins, and worked with Right Whale management with the maritime industry and the coast guard.

Q. About a 100 college students, maybe even more are following my blog now.  What’s your advice to them, for someone interested in marine biology/NOAA Corps, what should they be doing at this stage?

A. Great question. Volunteer! Find all the opportunities you can to volunteer, even if it’s unpaid.  Getting your face out there, letting people see how good a worker you are, how interested and willing you are, sometimes you will be there right when there is a job opening. Even if it seems like a menial task, just volunteer, get that experience. 

Q. NOAA accepts volunteers for ships every summer?

A. Yes, ecomonitoring and other programs takes students out for 2-3 weeks, but there are other opportunities like the local zoo.  Even stuff that isn’t related to what you’re doing. Getting that work experience is crucial.

Q. What’s the most challenging part of your job as an XO in a ship like this?

A. Living on a small boat in the middle of the ocean can be challenging for people working together harmoniously.  Just making sure everyone is happy and content and getting fulfillment for their job.

At the end of the interview, Claire handed me a stack of brochures describing the NOAA Corps and how you can become part of it. Please stop by my office (Math-Science 222) for a copy.

Personal Log

The seas have become decidedly choppier the past few days.  It’s a challenge to stay on your feet!  The decks lurch unexpectedly.  Things get tossed around if not properly anchored.  I have fallen just once (touchwood!) and was lucky to get away with just a scratch.  I’ve had to take photo backups of my precious field notes lest they get blown away.  They came close to that once already.

The ship has a mini library with a decent collection of novels and magazines plus a lounge (with the ubiquitous snacks!).  I found a copy of John Grisham’s The Whistler, and this has become my daily bed time reading book. 

The lounge and library on board
The lounge and library on board

Interesting animals seen lately

I started this blog with a photo of an exceptionally long arrow worm.  The cold waters have brought some other welcome creatures.  I created a virtual stampede yesterday in the flying bridge when I yelled Holy Mola!  Everyone made a mad dash to my side to look over the railings at a spectacular Ocean Sunfish (Mola mola) floating by.  The name Mola comes from the Latin word meaning millstone, owing to its resemblance to a large flat and round rock.  I have been looking for this animal for days!  Measuring up to 6 feet long and weighing between 250 and 1000 kg, this is the heaviest bony fish in the world.  The fish we saw was calmly floating flat on the surface, lazily waving a massive fin at us as though saying good bye.  It was obviously basking.  Since it is often infested with parasites like worms, basking helps it attract birds that prey on the worms.

mola mola
Ocean Sunfish Mola mola. We saw this behemoth lying on its side basking, waving its massive dorsal fin as though greeting us. They allow birds and other fish to pick their ectoparasites as they float (from baliscuba.com)

Another animal that almost always creates a stir is the dolphin.  Schools of dolphins (of up to 3 species) never cease to amuse us.  They show up unexpectedly and swim at top speed, arcing in and out of the water, often riding our bow.  Sometimes, flocks of shearwaters circling around a spot alert us to potential dolphin congregations.  Dolphins drive fish to the surface that are then preyed upon by these birds.  My colleague Allison Black captured this wonderful photo of Common Dolphins frolicking by our ship in perfect golden evening light.

common dolphins
Common Dolphins swimming by our ship (Photo by Allison Black)

Did You Know?

Molas (Ocean Sunfish) are among the most prolific vertebrates on earth, with females producing up to 300,000,000 eggs at a time (oceansunfish.org).

Parting shot

NOAA does multiple concurrent missions, some focused on fisheries, some on oceanography, and some hydrography.  It has a ship tracker that tracks all its ships around the world.  Our ET Stephen Allen kindly shared this image of our ship’s location (marked as GU) plus the locations of two other NOAA ships. 

location on shiptracker
Our exact location (GU) on 25 August 2019, captured by NOAA’s ship tracker (Courtesy Stephen G. Allen)

Jill Bartolotta: Sounds of the Deep, June 5, 2019

NOAA Teacher at Sea

Jill Bartolotta

Aboard NOAA Ship Okeanos Explorer

May 30 – June 14, 2019

Mission:  Mapping/Exploring the U.S. Southeastern Continental Margin and Blake Plateau

Geographic Area of Cruise: U.S. Southeastern Continental Margin, Blake Plateau

Date: June 5, 2019

Weather Data:

Latitude: 29°01.5’ N

Longitude: 079°16.0’ W

Wave Height: 2 feet

Wind Speed: 10 knots

Wind Direction: 128

Visibility: 10 nm

Air Temperature: 27.7°C

Barometric Pressure: 1021.3

Sky: few

Science and Technology Log

What is sonar?

Sonar is the use of sound to describe the marine environment. Sonar can be compared to satellites that use light to provide information about Earth, but instead of light, sound is used. It is used to develop nautical charts, detect hazards under the water, find shipwrecks, learn about characteristics of the water column such as biomass, and map the ocean floor. There are two types of sonar, active and passive. Active sonar is sonar that sends out its own sound wave. The sonar sends a sound wave (ping) out into the water and then waits for the sound to return. The return sound signal is called an echo. By assessing the time, angle, and strength of the return sound wave or echo one can learn many details about the marine environment. Passive sonar does not actively send out a sound ping, but rather listens for the sound from other objects or organisms in the water. These objects may be other vessels and these organisms may be whales or marine ecosystems such as coral reefs.

Sound waves move through the water at different speeds. These speeds are known as frequencies and the unit of measurement for sound is a hertz (Hz). Lower frequencies (example 18 kHz) are able to go farther down because they move slower and have more power behind them. It is like when a car goes down your street, pumping the bass (always seems to happen when I am trying to sleep) and you can hear it for a long time. That is because it is a low frequency and has longer wave lengths. Higher frequencies (example 200 kHz) move faster, but have less power. The sound waves should reach the bottom, an object, or biomass in the water column, but there may be no return or echo. High frequency sound waves are closer together. High frequencies give you a good image of what is happening near the surface of the water column and low frequencies give you a good idea of what is happening near, on, or under the ocean floor.

Type of Sonar on Okeanos Explorer

There are many types of sonar and other equipment aboard Okeanos Explorer for use during mapping operations. All have different capabilities and purposes. Together they provide a complete sound image of what is happening below us.

Kongsberg EM302 Multibeam Sonar

Multibeam sonar sends sound out into the water in a fan pattern below the hull (bottom) of the ship. It is able to map broad areas of the water column and seafloor from depths of 10 meters to 7,000 meters. Only the deepest trenches are out of its reach. It is the most appropriate sonar system to map seafloor features such as canyons and seamounts. The fan like beam it emits is 3-5.5x the water depth with a max swath range of 8 km. However, when you get to its depths below 5,000 meters the quality of the sound return is poor so scientists keep the swath range narrower to provide a higher quality of data return. The widest swath area scientists can use while maintaining quality is a depth of 3,300-5,000 meters. The user interface uses a color gradient to show you seafloor features (red=shallow and purple=deep).

Swath ranges for the multibeam sona
Swath ranges for the multibeam sonar at various depths. The y-axis shows the water depth in meters and the x-axis shows the swath width in meters. Photo credit: SST Charlie Wilkins, NOAA Ship Okeanos Explorer
Multibeam Sonar information
Some of the information that is collected using the multibeam sonar with labels describing their purpose. Photo Credit: NOAA OER


Backscatter uses the same pings from the multibeam. People use backscatter to model or predict physical or biological properties and composition of the sea floor. The coloring typically is in grayscale. A stronger echo looks brighter in the image. A weaker echo looks darker in the image. It gives you a birds-eye view of seafloor characteristics such as substrate density and seafloor features.

Backscatter and Bathymetry
Top image is backscatter showing you a birds-eye view of the ocean floor. The bottom image shows you what it looks like when backscatter is overlaid over the bathymetry layer. You are able to see intensity of the sound return, but floor features are more noticeable. Photo credit: NOAA OER


An Expendable Bathy-Thermograph (XBT) provides you with information on the temperature gradients within the water. When the temperature profile is applied to a salinity profile (taken from World Ocean Atlas) you are able to determine sound velocity or the rate at which the sound waves can travel through the water. When sound moves through water it does not move in a straight line. Its path is affected by density which is determined by water type (freshwater or saltwater) and temperature. Freshwater is less dense than saltwater and cold water is denser than warm water. The XBT information accounts for sound refraction (bending) through various water densities. When near shore XBTs are launched more frequently because the freshwater inputs from land alter density of the water and temperatures in the water column are more varied. XBTs are launched less frequently when farther from shore since freshwater inputs are reduced or nonexistent and the water column temperature is more stable. However, ocean currents such as the Gulf Stream (affecting us on this cruise) can affect density as well. The Gulf Stream brings warm water from the Gulf of Mexico around the tip of Florida and along the eastern coast of the United States. Therefore, one must also take into account which ocean currents are present in the region when determining the launch schedule of XBTs.

Loading the XBT Launcher
Senior Survey Technician Charlie Wilkins and Explorer in Training, Jahnelle Howe, loading the XBT launcher. XBTs are launched off the stern of the ship.
XBT Capture
Sound speed or velocity is determined by the density of the water, which is determined by temperature and salinity. Focus on the blue line in each graph. The first graph takes the information from the temperature and salinity graphs to determine sound speed. If we look at the first graph, we see that sound speed slows with depth. Sound speed slows because according to the second graph the temperature is colder making the water denser, thus affecting sound speed. Salinity does not vary much according to the third graph so its effect on density is most likely limited. Photo credit: NOAA OER

Simrad EK60 and EK80 Split-beam Sonar

Split-beam sonar sends out sound in single beam of sound (not a fan like the multibeam). Each transducer sends out its own frequency (example 18 kHz, 38 kHz, 70 KHz, 120 kHz, and 200 kHz). Some frequencies are run at the same time during mapping operations. Mapping operations typically do not use the 38 kHz frequency since it interferes with the multibeam sonar. Data collected with the use of the EK60 or EK80 provides information about the water column such as gaseous seeps, schools of fish, and other types of dense organism communities such as zooplankton. If you remember my “did you know” from the second blog, I discussed how sonar can be used to show the vertical diurnal migration of organisms. Well the EK60 or EK80 is the equipment that allows us to see these biological water column communities and their movements.

Water column information
Water column information collected with the EK60 or EK80 split beam sonar. If you look at the first row you can see, in the image to the left, the blue dots are at the top and in the second image the blue dots are moving back down into the water column as the sun rises. The process of organisms’ movement in the water column at night to feed is known as vertical diurnal migration. Photo Credit: NOAA OER

Knudsen 3260 Sub-bottom Profiler

The purpose of using a sub-bottom profiler is to learn more about the layers (up to 80 meters) below the ocean floor. It works in conjunction with the sonar mapping the ocean floor to provide more information about the bottom substrate, such as sediment type and topography features. Sub-bottom data is used by geologists to better understand the top layers of the ocean floor. A very low frequency is used (3.5 kHz) because it needs to penetrate the ocean sediment. It will give you a cross section of the sea floor so floor features can be detected.

Cross section of the ocean seafloor
Cross section of the ocean seafloor shows you substrate characteristics. Photo Credit: NOAA OER


Telepresence aboard the ship allows the science team to get mapping products and raw data to land on a daily basis. The science team can also live feed data collection to shore in real time. By allowing a land based shore team to see the data in real time you are adding another system of checks and balances. It is one more set of eyes to make sure the data being collected looks correct and there are no issues. It also allows a more collaborative approach to mapping, since you are able to involve a worldwide audience in the mission. Public viewers can tune in as well.  Support for the technology needed to allow telepresence capabilities comes in partnership with the Global Foundation of Ocean Exploration (GFOE). With GFOE’s help, the protocols, high-speed satellite networks, Internet services, web and social media interfaces, and many other tools are accessible when out to sea. The NOAA Office of Exploration and Research (OER) provides the experts needed to develop, maintain, and operate the telepresence systems while at sea, but also at shore through the Exploration Command Centers (ECCs) and the University of Rhode Island’s Inner Space Center.

Live interaction
Live interaction with Okeanos Explorer, Inner Space Center at URI/GSO, and a group of high school students. Photo credit: NOAA OER

All in all, the equipment aboard Okeanos Explorer is impressive in its abilities to provide the science team with a high quality and accurate depiction of the ocean floor and water column. The science team aboard is able to interpret the data, clean out unwanted data points, store massive data files on computers, and send it back to land daily, all while rocking away at sea. Very impressive and very cool!

Personal Log

I learned all about memes today. Apparently they are very popular on the ship. So popular, we are even in the middle of a meme contest. For those of you unfamiliar to memes like I was, a meme is a funny picture with a clever caption that makes you laugh or relates to something in your life. After my tutorial in meme making, we had a great time out on the bow of the ship playing corn hole and hanging out. The night was beautiful. The humidity subsided and there was a great breeze. After the sun set, I watched the stars come out and then went inside to learn more about the mapping process. I am starting to get a better understanding of what the science team is doing. You know the how and the why of it all. After I couldn’t keep my eyes open any longer, I made my nightly venture out onto the bow to look from some bioluminescence, the glittering of zooplankton in the night. A magical site. I will leave you wondering how the ocean glitters until one of my future blogs when I describe the process of bioluminescence.

Corn hole
General Vessel Assistant Sidney Dunn (left) and General Vessel Assistant Christian Lebron (right) playing corn hole on the bow at sunset.

Did You Know?

The SOFAR (Sound Fixing and Ranging) channel occurs in the world’s oceans between depths of 800 to 1000 meters in the water column. Because of the density and pressure around this channel, sound waves travel for an extended distance. It is thought that fin whales travel to this channel to communicate with other fin whales many kilometers away.