Tag Archives: marine chemistry

UGA Skidaway Institute scientists to study aerosol dust’s impact on life and chemistry in the ocean

A team of University of Georgia Skidaway Institute of Oceanography scientists has received a 4-year, $1 million grant from the National Science Foundation to study how dust in the atmosphere is deposited in the ocean and how that affects chemical and biological process there.

The research team of Clifton Buck, Daniel Ohnemus and Christopher Marsay will focus their efforts on a patch of the Pacific Ocean near Hawaii.

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Daniel Ohnemus (l) and Clifton Buck

“Our overall goal is to look at the aerosol loading and concentrations in the atmosphere, the rate that dust is deposited into the ocean and what happens to it once it is in the water column,” Buck said.

The chemistry of the ocean can be changed by the introduction and removal of elements, including trace elements which are present at low concentrations. In some cases, these elements are known to be vital to biological processes and ocean food webs. Near the shore, rivers are a large source for material from land to the ocean. Beyond the reach of rivers, and for most of the oceans, material blown from land through the air is the largest source of trace elements to surface waters.

“The ocean and the atmosphere are connected. What is in the atmosphere ends up in the ocean.” Ohnemus said. “Some part of what is in the ocean gets recycled back into the atmosphere, but mostly the movement is from the atmosphere to the ocean.”

The material enters the oceans dissolved in rain or by settling of dust particles. Understanding atmospheric sources of trace elements to the oceans is thus important to understanding both global chemical cycles and patterns of biological production. The team will look at trace metals like iron, which may appear in extremely low concentrations, but are essential to the growth of phytoplankton, the single-cell marine plants that serve as the base of the food web and produce approximately half the oxygen in the atmosphere. They will also look at other metals, like copper and cadmium, which are toxic and have a limiting influence on phytoplankton growth.

“Long-term atmospheric and ocean measurements are really hard to get at the same time in the same place, but that is what we are trying to do,” Ohnemus said.

Beginning in early 2021, the team will begin collecting aerosol samples at the Makai Research Pier on the southeast or windward side of Oahu. They will also undertake the first of six cruises to collect water samples at a spot in the Pacific known as the Hawaii Ocean Time-Series Station Aloha. This is a six-mile wide section of ocean approximately 200 kilometers from Oahu where oceanographers from around the world study ocean conditions over long time spans.

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This chart shows the location of the research field sites. Credit: Lee Ann DeLeo

A key goal of this project will be to obtain relatively frequent measurements over two full annual cycles. By taking weekly aerosol samples and water samples every few months, the researchers hope to be able to obtain a picture of how the atmosphere and the ocean change on a weekly, monthly or seasonal basis.

“It is important to point out that the dust transport over the North Pacific has a distinct seasonal cycle,” Buck said. “Dust concentrations are going to be different during the winter than they are in the summer.”

In the past there have been studies of aerosol dust concentrations in that region, but they were conducted at the top of the Mauna Loa volcano.

“That’s almost 12 thousand feet up, and not necessarily representative of what is being deposited in the ocean,” Buck said. “That is the leap we are trying to make here.”

The researchers chose Hawaii as the site for their field work for several reasons. Hawaii offers direct access to the remote, nutrient-limited open ocean. Hawaii also has strong seasonal fluctuations to its aerosol inputs, meaning there should be measurable changes over the two-year time series. The Hawaii Ocean Time Series has conducted regular research cruises to Station ALOHA since the mid-1980s, so there is already a historic collection of relevant data. From a practical standpoint, it also means the scientists will have regular access to those cruises to collect their ocean samples.

Although this project will not focus on marine plants, those plants are the reason the scientists want to answer questions about the marine chemistry.

“A very small amount of aerosol dust from a desert in China can provide enough nutrients to satisfy plant growth for weeks,” Ohnemus said. “So it can have a huge influence on which algae will grow where and how successful they are.”

Working with contractors from Florida International University, the research team will use a radioisotope of beryllium to measure the rate of atmospheric deposition. Beryllium-7 is created only in the upper atmosphere by the exposure of nitrogen and oxygen to cosmic rays, and has a half-life of 53 days. By measuring the concentration of beryllium-7 in samples, they will be able to estimate the deposition rate at which beryllium and other materials are being deposited on the surface.

The team will also contract with scientists at the University of Hawaii to collect aerosol samples on a more frequent basis than the Georgia-based researchers would be able to do themselves.

The project is funded by NSF Grant #1949660 totaling $1,074,114.

UGA Skidaway Institute scientist to spend winter 2020 locked in Arctic ice

Cliff Buck

Spending the Christmas holidays and the better part of January and February on a ship frozen solid in the Arctic ice cap isn’t most people’s idea of a great way to spend the winter. However, University of Georgia Skidaway Institute of Oceanography scientist Cliff Buck is planning to do just that. Buck is part of a major, international research project named Multidisciplinary drifting Observatory for the Study of Arctic Climate or “MOSAiC.” The goal of the project is to sail the German ice breaker Research Vessel Polarstern into the Arctic Ocean until it becomes locked in the ice and leave it there for a year, all the while using it as a headquarters for scientists to study Arctic climate change.

Climate change is occurring at a higher rate in the Arctic than in other regions. That rate of change is not reflected well in climate change models, mostly due to the lack of year-round observations in the Arctic.

“We care about this because the Arctic is turning out to be one of the more sensitive parts of the planet when it comes to climate change,” Buck said. “It’s warming at rates much higher than other parts of the world, and as it warms, many things are happening, such as the reduction in the expanse of sea ice.”

Those changes have implications on the means and rates that materials flow into the region, which, in turn, affect plant and animal life. Buck’s role will be to monitor the atmospheric deposition of trace elements like iron. Trace elements appear in the ocean in minute concentrations — parts per billion or even parts per trillion. However, they play a key role in the growth of phytoplankton — the tiny marine plants that form the very base of the marine food web and produce approximately half the oxygen in our atmosphere. In much of the world’s ocean, it is the presence or scarcity of iron that regulates the growth of phytoplankton.

Buck and his colleagues hope to develop a better understanding of how trace elements make their way from the upper atmosphere to the ice cap. They can arrive either as little particles, floating in the atmosphere and settling like dust, or they can fall as part of a raindrop or snowflake.

“In the Artic, the composition and abundance of aerosols tend to vary seasonally which is the reason it is important to get a series of observations over a long time scale to see how deposition rates of these aerosols change over the course of a year,” Buck said. “We care about that because in areas removed from river input and other continental influences, atmospheric deposition can be the primary source of trace elements like iron for the surface ocean.”

Buck and colleagues from Florida International University and Florida State University will use a technique utilizing a radioactive isotope of beryllium, itself a trace element, to measure the rate of atmospheric deposition. Beryllium-7 is created only in the upper atmosphere by the exposure of nitrogen and oxygen to cosmic rays, and has a half-life of 53 days. By measuring the concentration of beryllium-7 in samples, Buck will be able to estimate the rate beryllium and other trace elements are being deposited on the surface.

R/V Polarstern
Photo credit: Stephanie Arndt/Alfred Wegener Institute

The research team will take turns working on the ship in shifts of two months at a time. As many as 40 to 50 scientists might be on the R/V Polarstern during each shift, collecting samples and making a wide range of observations throughout the year. Buck is tentatively scheduled to be on board from mid-December 2019 through mid-February 2020.

“I really have no one to blame but myself for being assigned a winter shift,” Buck said. “It is very difficult to make these measurements during the winter, so it is very important to us to insure those winter samples are collected properly. When I said that out loud, they said ‘so I guess you want to go in the winter.’”

Although locked in the Arctic ice cap, the R/V Polarstern will not be stationary. The area where the researchers anticipate the ship will be frozen is subject to a surface current called the Transpolar Drift which propels sea ice from the East Siberian Sea to the Fram Strait, off the east coast of Greenland. The R/V Polarstern could drift as much as 1,500 miles during its year locked in the ice cap.

“The Arctic Ocean is a very interesting place with a lot of wind and a lot of physics going on up there,” Buck said. “You may not perceive the movement, but you will be moving.”

Buck’s participation in the MOSAiC project is funded by a four-year, $350,412 grant from the National Science Foundation Arctic System Science Program.

Molecular-level relationships key to deciphering ocean carbon

by Alan Flurry

From beach shallows to the ocean depths, vast numbers of chemical compounds work together to reduce and store atmospheric carbon in the world’s oceans.

In the past, studying the connections between ocean-borne compounds and microbes has been impractical because of the sheer complexity of each. Three University of Georgia faculty members—along with an international team of scientists—bring to the forefront technological developments that are providing scientists with the analytical tools needed to understand these molecular-level relationships.

Their perspective article appears March 7 in the Proceedings of the National Academy of Sciences. It focuses on dissolved organic matter, or DOM, in the world’s oceans as a central carbon reservoir in the current and future global carbon cycle.

“Dissolved organic carbon is an amazing and confounding molecular soup,” said Aron Stubbins, co-author and associate professor of marine sciences at UGA housed at the Skidaway Institute of Oceanography in Savannah. “It sits at the center of the ocean carbon cycle, directing the energy flow from the tiny plants of the sea, phytoplankton, to ocean bacteria. Though around a quarter of all the sunlight trapped by plants each year passes through dissolved organic carbon, we know very little about the chemistry of the molecules or the biology of the bacterial players involved.”

The carbon the microbes process is stored in seawater in the form of tens of thousands of different dissolved organic compounds.

Researchers thought they had a handle on how some aspects of the process works, but “a number of new studies have now fundamentally changed our understanding of the ocean carbon cycle,” said the paper’s lead author Mary Ann Moran, Distinguished Research Professor at UGA.

In the context of methodological and technological innovations, the researchers examine several questions that illustrate how new tools—particularly innovations in analytical chemistry, microbiology and informatics—are transforming the field.

From how different major elements have cycles linked though marine dissolved organic matter to how and why refractory organic matter persists for thousands of years in the deep ocean to the number of metabolic pathways necessary for microbial transformation, the article infers a scale of enhanced and expanded understanding of complex processes that was previously impractical.

The perspective article, “Deciphering Ocean Carbon in a Changing World,” was shaped in discussions at a 2014 workshop supported by the Gordon and Betty Moore Foundation and Microsoft Research Corporation. Moran’s research has been supported by the Gordon and Betty Moore Foundation’s Marine Microbiology Initiative.

Co-authors on the paper include UGA’s Patricia Medeiros, assistant professor in the department of marine sciences. Others involved are with the Woods Hole Oceanographic Institute; the Scripps Institute of Oceanography and the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego; University of Tennessee, Knoxville; Oregon State University; Columbia University; The Pacific Northwest National Laboratory, Richland Washington; the University of Washington; University of Oldenburg, Germany; Sorbonne Universités; and the University of Chicago.