Notes from the Field

NAAMES-III Expedition: September 9, 2017

September 11th, 2017 by Kristina Mojica

The Small Stuff Matters

The most important form of life in the ocean also happens to be the smallest. Phytoplankton provide the foundation of marine food webs, regulating global climate and the transport of nutrients and carbon. Phytoplankton populations fluctuate, sometimes growing high in numbers if they receive plenty of sunlight or nutrients. Other times, phytoplankton experience mortality, mainly from hungry grazers called microzooplankton (slightly larger carnivorous plankton) or from infectious viruses. As such vital components of the marine ecosystem, it is important to understand the balance between phytoplankton growth and death.

This is where we come in – our research team, which includes oceanographers from URI and UGA, are working to measure how often phytoplankton grow or die in the North Atlantic Ocean. Ultimately, we hope to link these findings of phytoplankton dynamics to larger-scale ocean and atmospheric measurements being made on the cruise.

On the cruise, we perform 24-hour incubation experiments with seawater collected from the water column. We sample the seawater the day its collected and a day later, measuring changes in the phytoplankton community using a range of instruments on board. One such instrument, the flow cytometer, allows us to count microscopic phytoplankton cells one-by-one. The flow cytometer takes up a sample and uses a laser to shine each cell as it passes by, distinguishing them based on specific size and fluorescence properties. After running a sample, we circle the populations, add some color to easily distinguish them and count the number of cells within each population. By comparing the number of cells gained or lost in a population each day, we can directly measure their growth and mortality rates!

Flow cytometry is just one technique we are employing on this cruise, but it is already helping to advance our knowledge of phytoplankton in the North Atlantic.

The flow cytometer we have on board the ship (left) and a typical plot (right) we see after a sample run, showing the different phytoplankton populations by color.

Written by Sean Anderson

NAAMES-III Expedition: September 8, 2017

September 11th, 2017 by Kristina Mojica

Most of us think that our everyday lives put us under pressure, but the real pressure – in a physical sense – happens deep below the ocean surface. On Friday, most of us in the NAAMES III science teams aboard the Atlantis performed an exercise that clearly demonstrates that pressure. The ship is always buzzing with science activities, but that day there was a different buzz, as all of us took breaks from our sampling routines and, as excited as little kids, grabbed markers of multiple colors to actively decorate Styrofoam cups with our favorite motifs, all the while chewing on candies. True to oceanographic tradition, the decorated cups would then be sent down to 3000 m below the ocean surface. Due to the pressure, when the cups come back up they have shrunk to a fraction of their original size. Many of the designs on the cups were inspired by ocean creatures, or by the sunsets and sunrises and the beautiful skies that we had been admiring from the ship. Favorite sports teams were also featured, as of course were the R/V Atlantis and the NASA planes that fly above our sampling region. We take the shrunken cups home as souvenirs of our time on the ocean.

SSSG Catie attaching cups to the CTD on board the R/V Atlantis

The cups go down securely attached to a sampling package made of various sensors and water sampling bottles known as a CTD, which is cast from the ship via a winch. CTD is an essential oceanographic instrument that occupies a central place in the NAAMES field campaigns. CTD is an acronym for conductivity, temperature, and depth, which are among the primary parameters that the instrument measures and give information about the physical structure of the ocean in the vertical dimension. Attached to the CTD are also probes that measure parameters such as oxygen and fluorescence. Fluorescence is caused by the dissipation of some of the energy contained in the light absorbed by pigments, such as chlorophyll, occurring within ocean microscopic plants known as phytoplankton. A portion of the absorbed light is emitted at another (longer) wavelength, stimulating fluorescence that can be measured by the probe, providing an estimate of the concentration of the phytoplankton.

NAAMES scientists with their decorated cups (left) and the shrunken cups after going down to 3000m (right)

As the CTD is cast downwards, the data its sensors collect are displayed in real time on a computer screen, attracting many of us around the computer avidly watching vertical profiles of the ocean.

The CTD room on board the R/V Atlantis (on the left) and typical CTD profile display (on the right).

We use the information to determine which depths present interesting features that will guide our sampling. On the up cast, the CTD can then be stopped at these specific depths to collect water that provides chemical and biological samples and is also used in experiments. Even if we find decorating Styrofoam cups fun, that is when we go back to our lab with the collected water that the true fun begins.

 

Written by Francoise Morison

NAAMES-III Expedition: September 7, 2017

September 10th, 2017 by Kristina Mojica

The Scripps research group focuses on aerosols, which are microscopic liquids and solids suspended in the air.  Aerosols may be formed over the ocean when wave generated bubbles burst and eject particles into the atmosphere.  Aerosols may also be formed from gas phase compounds released from the ocean that then react with sunlight and oxidants in the atmosphere.  Aerosols are important to climate as they act as seeds for cloud droplets.  The ability of water to collect on aerosols is determined by their size and chemical composition.  We have several instruments housed in our sampling van that we use to determine these properties.  The aerosols are sampled through an inlet that reaches 50 ft above the ocean surface.

The instrument that I work with is an Aerosol Mass Spectrometer (or AMS for short).  The AMS provides information on the chemical composition of the aerosols.  We typically look at a variety of organic compounds as well as nitrates, sulfates (both from sea salt and organic sulfates formed from dimethyl sulfide released by ocean biology), and other sea salt components (NaCl).  The AMS can also determine the sizes of the different aerosol components.

An interesting part of the NAAMES study is linking the atmospheric aerosol measurements with the chemical and physical properties of the ocean being measured by the oceanography teams.  These comparisons will help us better understand the processes contributing to aerosol formation over the oceans.

We will also be able to compare our ship-based aerosol measurements with those of the C-130 aircraft.  The C-130 can enhance the range of aerosol measurements by flying an accordion shaped pattern around the ship (upwind and downwind), which will let us see how the aerosols measured by the ship change over time.  The aircraft will also fly a vertical pattern, which will provide us with information on the vertical profile of the atmosphere.  That information is important for understanding the heights and stability (and potential mixing) of the different sub-layers of the troposphere.

The NASA LARGE C-130H Hercules aircraft flyby of the R/V Atlantis on 9/6/2017. The aerosol sampling vans with inlets can be seen on the upper deck (Scripps van on the left, PMEL van on the right).

Written by Derek Price

NAAMES-III Expedition: September 6, 2017

September 9th, 2017 by Kristina Mojica

Sea Sweep gently surfs

Generating aerosol

On the Atlantic

While some aboard the Atlantis are fighting bubbles with rigor (see September 1, 2017 post), the atmospheric chemists on the bow of the ship are busy generating them. Not the same ones that the biologists were battling in the earlier post, but new ones that mimic the production of sea spray aerosol by waves in the ocean.

To do this, we deploy a clever aerosol generator alongside the ship that we call Sea Sweep. The Sea Sweep injects clean air into the surface layer of the ocean to create many bubbles that pop and produce sea spray aerosol. We suck that aerosol up to take a multitude of samples and measurements for both our own group and other researchers as part of the NAAMES project.

The NOAA/Pacific Marine Environmental Laboratory (PMEL) Sea Sweep on the port side of the R/V Atlantis during bubble/aerosol generation.

Last night, just as we were getting ready to take a subset of our samples, we noticed our aerosol counts drop dramatically (from ~1,000 down to 100..then down to 10!). Upon investigation, it turned out our air compressor had a broken belt. Alas, we did not have a spare one with us (you can be sure we will have at least two next cruise!). Thankfully, the ship was able to provide us with a suitable substitute and we were able to get back to generating our bubbles with only a little hiccup. We are very grateful to the crew of the R/V Atlantis!

Written by Lucia Upchurch and Derek Coffman

University of Washington Joint Institute for the Study of the Atmosphere and Ocean

NOAA Pacific Marine Environmental Laboratory

NAAMES-III Expedition: September 5, 2017

September 9th, 2017 by Kristina Mojica

A Light Puzzle

Today we were able to finish our first official station of NAAMES 3! Our group, the UCSB Optics team, saw a whirlwind of activity as we deployed half a dozen different instruments to begin to characterize all the different ways that light interacts with the ocean. You could call us the most superficial of teams, where we only care what things look like, but we do really care about what things look like!

Our goal is to model how light behaves in response to all the different biological, chemical, and physical things that all the other teams here at NAAMES are measuring so that we can move these models to ocean-monitoring satellites so they can tell us what might be happening in the global ocean. In a nutshell, we do math with colors!

The underwater light field is like a giant puzzle, with all the pieces coming together in a unique way. You can actually begin to measure one set of pieces, the apparent optics, with your eyes. This is what the ocean apparently looks like based on all the things in it and how it is lit up by the sun. If you have ever gone scuba diving or looked at underwater photos, you’ve probably noticed how blue everything looks. Where did all the red go? Based on optical properties, different colors of light disappear at different rates as you go deeper. We can model how quickly certain colors disappear relative to others to get an idea of things like how much plankton or dirt or dissolved materials are actually in the water!

On the other side, we have the inherent optical properties, those that are inherently there no matter how bright or dark it is outside. People sometimes wonder why I’m out at 3AM and 11PM making casts in the middle of the night for optics, and it’s because we’re still getting great data! The instruments that measure the inherent properties are literally the flashiest ones we have. Our IOP (Inherent Optical Property) Package is basically a disco ball of lights. One instrument on the package works by flashing a very specific color of light out at the water and then recording what “bounces” back at the sensor. Another fires a laser and records how much that laser bends based on the size of the microscopic particles in the water. Yes, we fire bendy lasers. I love optics.

All in all, each instrument gives us a different piece of the puzzle. Once we get enough pieces of the underwater light field, we’ll be able to more effectively look at the oceans from satellites and get a sense of what’s happening globally in the ocean at a moment’s notice. We’ll shine some light on Earth’s final frontier.

Written by James Allen