The Phosphorus Man Cometh

By Matt A. Barr

Think of all your favorite fireworks, fertilizers, detergents, and sewage pits. Got them all in your head? Great. Now think of all your favorite bones, teeth, DNA, RNA, and cell membranes. Finally, think of all your favorite plants and algal blooms. What do these things have in common? Phosphorus, of course. This versatile element is critical to all life, and here at the School of Earth and Atmospheric Sciences, it is taken very seriously by Dr. Ellery Ingall and his team of researchers.

Due to its high reactivity (it explodes upon contact with air), phosphorus does not occur naturally as a free element on Earth. Instead, it’s most prevalent in mineral form as phosphates – one phosphorus atom with four oxygen atoms attached. These phosphates are mined and refined for use in agriculture and industry. One of the most common destinations for refined phosphate is fertilizers. While these fertilizers do serve a purpose in large-scale farming activities, they can ultimately end up in waterways and lead to algal blooms that threaten the health of freshwater and certain saltwater environments. Phosphates can also compose aerosol particles that are transported through the atmosphere and deposited in ecosystems that may be incapable of supporting excess phosphorus.

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Phosphorus is an essential nutrient to aquatic life. Too much phosphorus can spur growth beyond what a body of water can support, however. When this happens, algal blooms can starve other life of oxygen and cause significant die-offs of neighboring species. Here, an algae bloom indicates signs of eutrophication, Danube old arm, Szigetkozi Nature Reserve.

Phosphates form the backbone structures for DNA and RNA though, and phosphorus, separated from its mineral structures by organic metabolic processes, acts as a limiting nutrient in many terrestrial and marine ecosystems. This latter role makes the availability of phosphates to organisms a significant factor in determining any growth in those ecosystems.

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Phosphorus only occurs naturally on Earth as mineral compounds with other elements. Phosphorus is in its most stable form as phosphate.

The Eastern Mediterranean Sea is one such ecosystem that Dr. Ingall and his research team consisting of Amelia Longo, Julia Diaz, Michelle Oakes, and Laura King have focused on due to dust plumes that are deposited there from continental Europe and Northern Africa. The winds over Europe and North Africa gather up the dust and other aerosols containing phosphates and transport them to the Eastern Mediterranean. In a region such as this where phosphorus content would otherwise be relatively scant, it’s easier to observe what effects result from increased phosphorus deposition.

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Dr. Ingall and his research team analyzed samples from the Eastern Mediterranean to determine the phosphorus sources leading to increased aquatic growth in the region.

Specifically, phosphorus in aerosols – the microscopic particles that compose the dust plumes – is the subject of the Ingall Lab’s research. He and his team use a synchrotron located at Argonne National Laboratory to identify the composition, mineralogy, and solubility of different phosphorus species present in aerosols from the dust plumes. The synchrotron is a particle accelerator that exposes the aerosol particles to high energy X-rays. Using these X-ray measurements, Dr. Ingall can characterize an entire plume with the information derived from a few small samples. Amelia Longo led the effort to understand these plumes. It was determined that phosphorus compounds from the European sources were much more soluble in water and, therefore, impacted growth in the eastern Mediterranean to a greater extent than those from North African sources. This came as something of surprise because previous studies and years of satellite data showed that higher quantities of phosphorus were being deposited by the North African plumes. While it was true that more phosphorus was coming from the North African plumes, this phosphorus was much less soluble than what was present in the European plumes, meaning relatively little of the North African phosphorus was affecting the growth of aquatic organisms in the region. Furthermore, the more soluble European aerosol phosphorus was organic in nature and appeared to originate from bacterial sources, whereas the less soluble North African phosphorus was locked up in minerals and lacked organic components.

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Dr. Ingall’s students help collect samples to be analyzed for phosphorus content.

Using the synchrotron, Dr. Ingall and his team have analyzed a variety of sample mediums for elements other than phosphorus as well. Before applying this technique to the study of phosphorus, Dr. Ingall was involved in researching iron, another limiting nutrient in the oceans. Taking samples from sites across the world and studying them with the help of the synchrotron, Dr. Ingall has identified how iron is used by diatoms whose activities greatly affect the availability of iron for other marine organisms. In Antarctica, these diatoms – microscopic unicellular organisms – appear to be storing iron in the silicate shells they develop as a barrier between themselves and the water. The exact purpose for this is unknown because, according to what Dr. Ingall and his team have observed, the iron stored in their shells is more than what the diatoms require for typical metabolic activities. Research into this question is still ongoing and has been primarily the work of Amelia Longo, who just completed her Ph.D. and Julia Diaz, one of Dr. Ingall’s former grad students, who is now an assistant professor at the Skidaway Institute of Oceanography in Savannah, Georgia.

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The synchrotron, a particle accelrator used by Dr. Ingall and his researchers, assists scientists across a variety of disciplines. It is housed at Argonne National Laboratory outside of Chicago, IL.

Along with his studies of phosphorus and other elements in aerosols, Dr. Ingall is in the process of developing new research into the composition of urban aerosols. In conjunction with Dr. Rodney Weber, an atmospheric chemist here at EAS, Dr. Ingall hopes to use the power of the synchrotron to analyze aerosol samples taken from right here in Atlanta. Characterizing the components of these aerosols can go a long way towards understanding the health risks associated with increased human exposure to toxic metals present in aerosol pollution. It may also shed light on some of the lesser-known atmospheric processes that cause the reduction of those metals. This reduction – an exchange of electrons between two species – typically results in these metals having higher solubility, making them more susceptible to dissolving in waters that ultimately end up in our water supply.

As always, be sure to check out our EAS website and Dr. Ingall’s page for more information.

 

A changing river: Measuring nutrients fluxes to the South China Sea

Below is a fascinating insight into GT EAS oceanography research, in conjunction with the School of Biology, that’s happening right now in the South China Sea. Many thanks to Dr. Bracco and undergrad Riannon Colton for sharing their experiences with us! We will be posting updates from their research here regularly. Be sure to take a look at Riannon’s blog to read all about the life of an oceanography researcher at sea!

Credit: Dr. Annalisa Bracco

Why Vietnam?

Anthropogenic pressures are threatening Vietnam’s coastal waters despite their vital role in the regional and national economy. Policies and developments in the next ten years will determine the chances to preserve both the Mekong Delta – that is subsiding at an alarming rate – and Vietnam’s relatively pristine coastal ocean. The socio-economical impacts of maintaining current practices in light of the challenges ahead would affect millions of people.

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The Mekong River is a critically important resource for millions of people living in Southeast Asia. Its delta and the waters it delivers to the South China Sea are vital to the coastal communities that depend on it.

A few facts

The Mekong Delta is largely used for agricultural production (mostly rice), but aquaculture has been rapidly increasing at the expense of mangrove and hardwood forests. Those and other land use changes are contributing to increased nutrient loading to the Mekong River waters and in turn to the Vietnamese portion of the South China Sea, promoting coastal and offshore eutrophication.

In the near future, additional and larger anthropogenic forcings will profoundly alter the linkages between the Mekong system and the South China Sea, which supplies a critical part of Vietnam’s seafood needs.  Recent and planned construction of dams and reservoirs in the Mekong Basin will fundamentally change the discharges of water, sediment, and nutrients to the ocean. By 2030, the construction of 11 new reservoirs in the lower Mekong basin, together with 62 hydropower dams distributed along the Mekong and its major tributaries in both China and Vietnam will reduce the mean seasonal flow cycle (by up to an order of magnitude) and sediment loading (up to 80%) of the Mekong River.  The diminished freshwater and sediment input will sharply reduce nutrient supply and modify nutrient cycling, altering the biogeochemistry and circulation of the whole basin in ways as yet unexplored.

At this time there are no studies or initiatives to evaluate the connections between regional policy decisions and the future of the South China Sea marine ecosystem. There are limited capacity building initiatives to train marine scientists on the trans-disciplinary research that is so urgently needed to address this major ocean threat.

Our contribution so far

Dr. Joseph Montoya (School of Biology) and Dr. Annalisa Bracco (EAS) have the extraordinary opportunity to conduct two research cruises on the R/V Falkor to the South China Sea, one ongoing and a second one in September of this year through funding –in the form of ship time – from the Schmidt Ocean Institute. Joining them are Riannon Colton (EAS undergrad), Caroline Reddy (Biology, technician) and Ana Clavere Graciette (Biology, postdoc).

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Scientists boarding the R/V Falkor for the first time in Nha Trang, Vietnam on June 1st 2016. They departed Nha Trang June 3rd and arrived to the first station on the 4th in the early morning. (courtesy of Riannon Colton)

The goal of these research cruises is to provide a critical baseline for understanding the impacts of the changes under way in the river delta and adjacent ocean waters by characterizing physical and biogeochemical conditions of the coastal waters affected by the Mekong River plume through a broad survey during the critical Southwest Monsoon season (June to September).

It is the first effort of this sort on a US research vessel in the past 30 years.

Scientists from Columbia University and the Leibniz-Institute für Ostseeforschung in Rostock, Germany join us, together with Vietnamese colleagues at the Institute of Oceanography in Nha Trang and at the Ho Chi Minh City University of Science.

The Vietnamese coastal waters are particularly rich in fish during the summer season. This is due to the elevated concentrations of nutrients (nitrogen, phosphorous, silica, iron…) within the surface ocean layer where photosynthesis can take place. High chlorophyll levels then cause zooplankton blooms that in turn attract predators (fish) and fishing vessels. Those nutrients are supplied to the upper water column where they are consumed by phytoplankton, through wind-driven upwelling (the seasonal monsoonal winds tend to push the water along the coast towards the north, bringing more water from underneath at the surface) and/or by the Mekong River, whose waters are particularly rich in nitrogen and phosphorous collected while streaming across China and Vietnam.

Today we are sampling our second station, near the Vietnam coast and within the coastal area impacted by wind-driven upwelling. Further south elevated concentrations of chlorophyll are linked less to upwelling and more to the abundance of nutrients associated with the Mekong River outflow.

Satellite Data

Satellite images of SST (sea surface temperature) (left) and chlorophyll (right) on June 4, 2016. Colder SST are associated to wind-driven upwelling, while elevated chlorophyll levels can be seen in upwelling areas and in waters modified by the Mekong River plume. Stations covered so far are indicated in both images by white dots. (Courtesy of Ajit Subramaniam)

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Fishermen worried that we could be cutting through their lines on June 5th, 2016 at our second station. (A. Bracco)

Keep checking in to follow along as our students and faculty continue on this important mission to understand how the Mekong River Delta may be changing in the very near future.

That’s No Moon…

By Matt A. Barr

The prospect of life existing on other worlds has manifested itself in human culture for millennia.  In a way, aliens have been visiting us ever since we could communicate.  They’ve been the subject of our stories, our works of art, and even our religions, conjuring vivid worlds and exotic forms limited only by the imaginations of those who entertain them.  Science fiction is often the realm of the alien, but very much embedded in fact is the potential to find alien life right here in our own solar system.

As discussed in previous posts, the conditions under which life as we know it may exist must include the presence of liquid water.  Microbial life stretches our definitions of those conditions, and microbes are what we’re likely to find if we do discover alien life.  With the recent discovery of flowing water on Mars, as well as our increasing understanding of microbiology, finding life on other worlds seems to be simply a matter of time.  Luckily, we know what microbial life looks like here on Earth, and we know what conditions it can thrive in, meaning we can minimize that time by pointing our sights toward the stars to find where else those conditions might exist.

It turns out, they exist on Europa.

If there’s life anywhere else in our solar system, it’s probably on Europa.  Europa is a mysterious icy moon orbiting Jupiter that has gripped the curiosity of planetary scientists for several decades.  First discovered by Galileo in 1610, it would be more than four centuries before anyone turned their attention to the secrets it may hold.

While telescopes have been trained on Europa for some time, NASA’s Galileo mission in the late 1990’s produced some tantalizing data about the moon.  Europa appears to be the most active planetary body in our solar system besides Earth.  It’s estimated that roughly 100-150 km of an outer shell consisting of ice and a subsurface ocean completely encircle Europa’s silicate crust, and the interaction between these three features on Europa is of great interest to the scientific community.

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Europa – one of Jupiter’s four Galilean Moons. Its surface offers an exciting prospect for hosting alien life.

Dr. Britney Schmidt, a planetary scientist at the Georgia Tech School of Earth and Atmospheric Sciences, and her research team, consisting of graduates Heather Chilton and Jacob Buffo, and undergraduate Josh Hedgepeth, are fascinated by the potential to harbor life that Europa holds.  Understanding Europa’s planetary processes is critical to answering its habitability questions though.  By conducting important research at ice shelves in Antarctica, specifically at the areas where ocean and ice directly interact with one another, Dr. Schmidt and her team hope to develop a working analog to what’s happening at the same types of physical boundaries on Europa.  Doing so would go a long way towards answering some of those questions.

At Antarctica’s McMurdo Ice Shelf, Dr. Schmidt and scientists from several other universities collaborate to gather data about the ice by sending robotic probes into the water below.  As part of a project known as SIMPLE (Sub-Ice Marine and PLanetary-analog Ecosytems), funded by NASA’s Astrobiology Science and Technology for Exploring Planets program, multiple expeditions scheduled over several “seasons” offer extraordinary opportunities to deploy up to five different submersibles into these frigid, unexplored waters.  These submersibles are used to collect samples, make observations about the water column, and seek to determine what processes govern the highly dynamic relationship between the surface of the ocean and the bottom layer of the ice shelf.  One of these submersibles, the Icefin, was designed and built by Dr. Schmidt’s startup here at Georgia Tech, and is slated for new upgrades between now and the upcoming Antarctic field expeditions.  These upgrades will allow the Icefin to operate in much wider areas than are currently possible to explore.

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One of the submersibles used to explore the waters beneath Antarctica’s McMurdo Ice Shelf.

We know that the Antarctic ice shelves can serve as analogs for Europa’s ice shell, but is there anything about Europa besides its liquid water that indicates the possible presence of life?  It’s not so much that liquid water exists on Europa as it is the reasons why the water is there in the first place.  Scarred with massive crevasses and chasms, Europa’s icy surface tells the story of significant geologic activity below.  One hypothesis for the source of this geologic activity is that Jupiter’s gravity is pushing and pulling on Europa, depending on the relative position of one to the other.  This is similar to the Earth-moon gravitational relationship we experience here, except that rather than merely changing the tides, Jupiter causes Europa’s interior to flex such that the resulting friction is likely causing Europa to heat up.  This thermal energy is robust enough to maintain liquid water above Europa’s crust.  Being outside of the habitable zone, however, Europa’s liquid water freezes over at a specific, as yet unknown depth to form the ice shell we observe.

This heating of Europa’s interior seems to result in the geologic activity that transports non-ice material from Europa’s crust toward its surface.  This material is visible to us in the form of dark reddish-brown areas scattered all across Europa’s surface, and it’s these areas that are the most likely candidates for hosting the first alien life we could encounter, to say nothing of what might exist in the ocean itself.  Similar non-ice material – material that happens to support life – is consistently observed in ice shelves on our planet.  The ocean-ice-continent interaction occurring beneath these ice shelves, powered by the earth’s geologic activity, deposits this material into the ice via convection processes.  The thinking goes that if we can understand how that’s happening on Earth, we will understand how it might be happening on Europa also.

ice shelf life

An ice shelf in Antarctica changes colors at locations where non-ice material is transported to its surface from the waters below. These areas are teeming with microbial life. Is something similar happening on Europa’s surface?

As it happens, habitability questions are also climate science questions.  Dr. Schmidt’s research ends up serving another purpose aside from understanding how alien life might develop on ice moons.  Her team’s submersibles are looking at how the oceans change the ice shelves and vice-versa, which addresses some particularly crucial gaps in our knowledge of the mechanics governing how climate change affects our Polar Regions.  Killing two birds with one stone is something we like to do here at Georgia Tech.

shelf process

Understanding how the ice, ocean, and continental shelf interact at crucial ice shelf locations helps Dr. Britney Schmidt and her team answer questions about both climate science and planetary habitability.

A final note of congratulations is in order.  Dr. Schmidt has recently been appointed to the science definition team for NASA’s Large UV/Optical/Near-Infrared (LUVOIR) telescope project.  She also has a few other exciting announcements whose releases we don’t wish to precede here, but she’s representing Georgia Tech and EAS in some pretty great ways.  Check out EAS in the coming days and weeks for the details.

Update: We’re proud to announce that Dr. Britney Schmidt has been selected to join the board of directors for The Planetary Society.  For more info about this appointment, see the Georgia Tech College of Sciences story.

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Planetary Society CEO Bill Nye pins Dr. Britney Schmidt with the Planetary Society logo pin following her appointment to the board of directors.