Posts Tagged ‘scientist’

Field stations and marine labs join forces to tackle national environmental challenges

March 20, 2013

A world threatened by extreme weather, invasive species, emerging disease and increasing uncertainty needs the scientific capacity to face those challenges. Natural laboratories around the country, which have been placing researchers on the front lines of understanding and managing environmental change for a century, form the building blocks of that capacity. The Organization of Biological Field Stations and The National Association of Marine Laboratories has released a report showing how scientists in communities across the continent respond to emerging questions in flexible and nimble ways, and are poised to work together to contribute to global solutions.

James Sanders

James Sanders

The report was supervised by a steering committee of seven scientists, including Skidaway Institute of Oceanography director James Sanders. Also, Skidaway Institute scientist Jens Nejstgaard participated in the workshop that contributed to the report.

Field stations and marine labs (FSMLs) are the primary places scientists go to study environmental processes in their natural context, and as such they harbor the knowledge of the past that we need to predict the future. They host thousands of individual researchers at hundreds of locations, and are the birthplace of many of the innovations and discoveries that drive environmental science today. Recent large-scale initiatives, such as the National Ecological Observatory Network (NEON) and the Ocean Observatories Initiative (OOI), as well as the longer-running Long-Term Ecological Research (LTER)

network, depend on existing FSML infrastructure. The novel insights these new observatories generate

Jens Nejstgaard

Jens Nejstgaard

will stimulate complementary research at many more field stations and marine labs.

However, only a small fraction of FSMLs participates in these broader-scale scientific initiatives. NEON and LTER represent ten per cent of the available long-term, place-based, multiple-investigator environmental research sites. The report, “Field Stations and Marine Laboratories of the Future: A Strategic Vision,” is based on a national workshop and survey and on input from the broader scientific community. The report recommends creating a Network Center to catalyze broader-scale science and to facilitate participation in coordinated environmental efforts. For example, a stronger network of FSMLs could contribute to evolving national and international programs such as the sustained National Climate Assessment or the Group on Earth Observations Biodiversity Observation Network.

Field stations and marine labs have the flexibility and the logistical and intellectual capacity to support novel experimental approaches across tremendous ecological diversity. Collectively, they represent billions of dollars of investment in research infrastructure, including and tools, and they have trained generations of environmental scientists.

This report is a first step in making sure the nation’s investment in field stations and marine labs continues to meet the dynamic and changing needs of scientists, students and the public they serve.

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The National Association of Marine Laboratories (NAML), organized in the late 1980’s, is a nonprofit organization of over 120 members employing more than 10,000 scientists, engineers, and professionals and representing marine and Great Lakes laboratories stretching from Guam to Bermuda and Alaska to Puerto Rico. The member institutions of the National Association of Marine Labs work together to improve the quality and effectiveness of ocean, coastal and Great Lakes research, education and outreach. Through these unique national and regional networks, NAML encourages ecosystem-based management, wise local land management and the understanding and protection of natural resources.

 

The Organization of Biological Field Stations (OBFS) is a 501(c)(3) nonprofit that represents field stations throughout the world. The mission of OBFS is to help member stations increase their effectiveness in supporting critical research, education, and outreach programs. OBFS pursues this goal in a manner that maximizes diversity, inclusiveness, sustainability, and transparency.

 

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Skidaway Institute searching for two faculty positions

October 11, 2012

The Skidaway Institute of Oceanography is currently seeking applications for two faculty positions.

 Trace Element Geochemist – This is a faculty position at the Assistant Professor level in trace element geochemistry. Applications from more senior candidates will also be considered. The successful candidate must have a Ph.D. and is expected to develop an active, extramurally funded research program. We are particularly interested in a collaborative colleague who can demonstrate experience in conducting field-based, interdisciplinary research in estuarine, coastal and/or marine environments.

For additional details, see the full job description and application guidelines at: http://www.skio.usg.edu/aboutus/jobs/1348248214.pdf

Marine Environmental Chemist – This is a faculty position at the Assistant Professor level in environmental chemistry, with interest in organic contaminant chemistry in the marine environment. Applications from more senior candidates will also be considered. The successful candidate must have a Ph.D. and is expected to develop an active, extramurally funded research program. We are particularly interested in a collaborative colleague who can demonstrate experience in conducting field-based, interdisciplinary research in estuarine, coastal and/or marine environments.

For additional details, see the full job description and application guidelines at: http://www.skio.usg.edu/aboutus/jobs/1348248079.pdf

A Day in the Life of a Citizen Scientist

June 21, 2012

Skidaway Institute volunteer scientist Nancy Tenenbaum recently travelled to Norway, to work with fellow Skidaway scientist Dr. Stella Berger. She described her experience in the form of a letter to her mentor, retired Savannah business leader and Skidaway Institute supporter,  Howard Morrison.       

Dear Howard,

Having had a few days to settle in here and wishing I could have packed you in my suitcase as well.  I am going to let you share the day with me through this letter.  I am in Espegrend, Norway, with a phytoplankton research project called Phytostress.  The word “stress” takes on a new meaning with this project. There are only a hand full of students and professors here to manage twelve mesocosms and three experiments.  In the course of the next two weeks I know I will need your encouragement and advise.

Rule #1 is “NEVER give up”. Howard Morrison

So, let the day begin.

7:00 AM

Taped to the window in my dorm room is a thick, black garbage bag to keep out the midnight sun.  Light at any hour after 10 pm is your worst enemy! Block it out at all costs. You might find it a bit challenging to navigate in my tiny dorm room. Most certainly it is not the spacious Civil War home, Lebanon Plantation, that you reside in. Through an open window in the kitchen field station birds sing incessantly. Fresh coffee waits patiently for the early riser made by Maria Segovia, the principal investigator of Phytostress. Norway has no version of half and half cream. Flotte,, heavy cream., is it. Putting a small amount in my coffee cup I think about the potential threat for artery clogging. Will I survive the day? On the wooden counter top a Norwegian breakfast of various cheese, lox, fruit muesli and a hardy multi-seed rye bread await.

View from the field station kitchen window.

 

Another view from the kitchen window

7:30 AM

You will need a jacket this morning as it is cool, about 11 degrees C (52 degrees F).  The fiord water sparkles in the sunlight.  On the hillside edelweiss, purple clover and yellow buttercups dance with the morning breeze. Compared to the weather when I was here in March, this is heaven.

Let me explain this project to you using an abstract provided by Maria Segovia, the principal investigator, for Phytostress:

Under the global change scenario around 40-50% of the CO2 emitted by anthropogenic activities is accumulated in the oceans causing acidification and increasing the availability of dissolved CO2 to primary producers (phytoplankton, algae, etc.). To understand the regulation of the carbon cycle it is basic to determine the interaction of the main factors controlling primary production in the ocean. The increase of UV radiation due to ozone loss can reduce the oceanic phytoplankton CO2 sinking capacity up to 2%. Concomitantly, the scarcity of micronutrients, such as iron, can affect the composition, functioning and growth of phytoplankton. However, although up to date there are several studies about the effect of UV on iron ocean speciation, there is none about the interaction between CO2, Fe (iron) and UV in phytoplankton, and the underlying mechanisms has not been elucidated yet. Equally, there is evidence of massive cell death phenomena in phytoplankton communities that can account for a great loss of biomass amount, altering diversity and hence affecting the carbon cycle. The proposed experiments, will lead us to a better understanding about the functions of marine phytoplankton as well as to determine how changes in CO2, UV and Fe availability control the fate of primary production in the ocean, regarding biomass and diversity loss.

In an introductory email before the research in May, Maria wrote that this mesocosm project is a dream come true for her.

8:45 AM

Howard, we are now at the dock.  I know how much you love to ride in boats.  Even though the ride to the raft will be quick it could be chilly. The swans that graced the fjord in March are gone.  Truthfully they were noisy, mean and not very white, like their counterparts in fairy tales.

Scientists and Ph.D. students, who are scheduled to sample water today, gather at the dock with sixteen, 25-liter carboys. Clothed in Healy Hansen immersion suits or only a life jacket they board small motorboats for the mesocosms.

You are now at the mesocosm raft.  Be careful on exiting the boat as the concrete raft moves with the current making its surface slippery. There are twelve covered mesocosms that are tethered to this raft.  A decoy hawk is mounted on a pole to scare off birds. It does absolutely no good! Birds actually seem attracted to it. Water is sampled by pumping H2O though a plastic meticulously washed tube into carboys. Full carboys of 25 liters are then loaded onto the boats, delivered to land and hauled up a hill using a flat wagon and human strength.

The mesocosm raft

THE MESOCOSMS

We are about to enter the lab when I spy a single wild yellow rose in full bloom. Immediately I am reminded of Antoine de Saint-Euprey’s story, The Little Prince. In this children’s book the rose is essential to the novel’s drama. Carefully tended by the prince, she is his motivation for leaving and returning to his planet. The rose in this book represents love, an invisible but essential emotion. If no passion exists to nourish life then the question presented is: can life survive? My passion extends to the invisible life of phytoplankton. They are in fact the unseen art forms. Simple, yet complex their balance in the food web is essential for life.

Howard, you often sign your emails with the quote: “Only those who can see the INVISIBLE can accomplish the IMPOSSIBLE!” Patrick Snow, Author, Creating Your Own Destiny

Armed with those words, I will take you into the lab hoping to have a productive day.

Actually the lab rooms are right out of Dr. Seuss!  Wacky and wonderful the equipment is dormant waiting for creative direction.  Machines hum and filtering systems wait expectantly. Life in the lab is a clandestine life unto itself.

We will need to double glove for this next task.  An elaborate washing protocol is the first order of duty.  Each sampling bottle must be washed with Deacon water, then immersed and soaked in HCl and finally rinsed five times with Milliq. H2O. As this involves a Fe (Iron) limitation experiment it becomes imperative to remove all possible traces of containment iron. This is a very time consuming process.

 

Ph.D students Charo, Armandoand and Candlera

The Espegrend Lab

10:30 AM

Dr. Stella Berger and I are on the microzooplankton team.  Microzooplankton can be defined as greater that 0.2-20 micrometers in size, which includes ciliates, dinoflagellates and diatoms. She is also working on a dilution experiment that she designed.

Dr. Stella Berger in command of the motorboat

Stella Berger with her dilution experiment

We return to the boat with Dr. Jose Fernandez from Malaga, to sample mesocosms numbers 1-6 and the fjord. Our samples are brought to our cold room. Part of every sample is then labeled and stored in covered boxes. Some are viewed as live slides in the inverted microscope. This is my favorite part of the day. Seeing the phytoplankton move and interact is just amazing. When I was here in March, I had the rare opportunity to meet and work with Andrei Sazchin. Dr. Sazchin is a Russian phytoplankton taxonomist.

Stella begins running her samples through a Flow Cam. Every cell is photographed and organized into libraries for later study. Each mesocosm sample involves a thirty-minute run process.

Flow Cam display of samples cell by cell

1:20 PM

I have a brief SKYPE conversation with my mentor and close friend, Sandra Nierzwicki-Bauer, Director of the Darrin Fresh Water Institute at Bolton Landing, Lake George, New York.

It does fact take a village of mentors to maintain the privilege of representing Skidaway Institute as a citizen scientist. Dr. Marc Frischer and Dr. Stella Berger are also instrumental in guiding me on scientific path.

2:30 PM

Lunch.  I am the only American here.  The Spanish lunch have a late, protracted lunch experience.  This long, heavy lunch is followed by lengthy scientific discussions in Spanish.

3:00 PM

Hope you are ready for a quick refreshing walk. The path by the fjord is a perfect place to reflect and regenerate. Bergen is a dichotomy. Look beneath the perfect postcard landscape and you will discover an ugly history of Nazi infiltration, which happened during WWII.

On the hillside adjoining the field station is the “castle.”  A Nazi once owned and lived in this forbidding residence. Inside, according to the locals, are memorabilia including swastikas that cover the walls.  Just looking upon it reminds me that six million Jews died as a result of Hitler.

Turning back to the water we are accosted by the smell of wild roses and rhododendron.  Seagulls cry. The sound of the water is soothing as it covers rocks and sand on a small beach.  Tiny islands with houses dot the fjord.  You can feel the ancient pulse of the land.  It emanates from the soil. Life despite its brief encounter with chaos and death has moved forward in a beautiful, peaceful way.

3:45 PM

Back in the lab we are ready to take the sample water for chlorophyll a (Chl a) is filtering in duplicate.  The lights are turned off and sunlight blocked by a makeshift shade as it excites the chlorophyll. A reading skewed by light will not be accurate. Once the water is filtered, the filter is put in a falcon tube, extracted with 90% acetone and then put in a covered box in a refrigerator where they stored for 6-24 hours.  The next day samples are measured by a fluorometer. This device measures parameters of fluorescence determining the amount of Chl a in the sample.

Filtering for chlorophyll a

 

Fluorometer

5:00 PM

We are back at a hood with an exhaust fan. After we have double gloved, each bottle will be immersed in hydrochloric acid for two hours.

6:00 PM

At some point every day it is good protocol update a lab notebook with general thoughts and data for the day.

7:00 PM

Stella has just finished running the last sample in the Flow Cam.  Slides from the inverted microscope used during the day are carefully washed.

7:30 PM

Dr. Jose’ Fernandez, Armando Olmo and I are on cooking duty tonight for 16 hungry people. You can pour the wine Howard to keep us happy while we cook. Tonight we will prepare paella. a traditional Spanish dish. This is a secret recipe of Jose’s grandmother.  I am chopping vegetables and hoping to learn the recipe for this famous meal. What I did manage to get from Jose’ is that the rice must absorb the flavors of the meat and vegetables. Timing apparently is everything.  So thanks to Jose the paella was delicious and a great success.

10:00 PM

The scientist and students sit down for dinner at a long narrow wooden table which seats at least 25. Most of the conversation is in Spanish.  Some students go back to the lab after dinner to finish up.

11:30 PM

Howard, there is something about the Norwegian blue hour that is pure magic.

The blue hour, not quite at sunset, floods the landscape with a purplish blue hue.  Maria’s two children are still running around with abundant energy. Laughing, and singing they are so undeterred by the hour.  I on the other hand am jet lagged and exhausted.  From my room I hear Maria’s husband calling his son Rodrigo to come inside.

Midnight sun

 

Sunset at the mesocosm raft. Photo by Maria Segovia.

Thanks for sharing the day with me!

Good night from the land of the midnight sun.

With love,

Nancy Tenenbaum –Citizen Scientist, Skidaway Institute of Oceanography

Stubbins joins Arctic cruise

June 19, 2012

Skidaway Institute scientist Aron Stubbins has spent the last couple of months working in Germany. He reports in on a cruise he is about to join.

I’m off to the Arctic on Germany research vessel Polarstern.

I will be collecting samples to determine the export of dissolved black carbon from the Arctic to the Atlantic Ocean. The cruise will transect Fram Strait, the major gateway for the exchange of water and dissolved material between the two ocean basins. Today we will leave Bremerhaven in Germany, site of the Alfred Wegener Institute which houses the R/V Polarstern.

In a few days we will reach Svalbard and begin a transect from there towards Greenland following 78.5 degrees north. During this transect we will first cross the West Spitsbergen Current (WSC) which carries warm Atlantic waters north into the Arctic Ocean. This is the northernmost extent of the Gulf Stream that originates in the Gulf of Mexico and travels past Georgia and Savannah at the edge of the Georgia shelf.

We will then transit west towards Greenland, breaking ice as we go. In this part of the cruise we will collect water samples from the East Greenland Current (EGC). This carries cold, polar water south into the Atlantic Ocean. A figure of the currents is shown at http://www.whoi.edu/science/PO/people/pwinsor/project_ao02.html.

My work will look at the amount and type of dissolved organic carbon that these two massive currents carry north (WSC) and south (EGC). Our progress can be followed in real time at http://www.awi.de/en/infrastructure/ships/polarstern/where_is_polarstern/. This site will also post weekly updates about life and science aboard R/V Polarstern.

The cruise will end in Longyearbyen on Svalbard where I will collect some samples to continue ongoing investigations into the sources and nature of glacier carbon (http://www.skio.usg.edu/?p=research/chem/biogeochem/glaciers).

Global warming may mean big changes to marine ecosystems

July 20, 2011

As the Earth’s climate continues to warm, what kind of effects will we see in the ocean and the world in general? Seeking the answer to that broad question is one of the reasons scientists from the Skidaway Institute of Oceanography are working with an international team of scientists on an experiment in Bergen, Norway.

“There is really no doubt that our planet is changing,” said Skidaway Institute scientist Marc Frischer. “Levels of carbon dioxide are increasing, and we are seeing changes in climate. There is very little controversy about that anymore.”

According to Frischer, scientists need to investigate what those changes will mean to life in the ocean — from the tiniest bacteria up to fish and larger organisms.

“Those are the kinds of questions that are important to us humans, because we are dependent on the life in the oceans for our existence here on Earth,” added fellow Skidaway Institute scientist Jens Nejstgaard.

Frischer, Nejstgaard, Skidaway Institute research coordinator Stella Berger, and graduate student Zachary Tait are part of a team of 37 scientists who have come together from 13 countries to join their individual expertise in an effort to solve some of these very complicated questions.

Skidaway Institute mesocosm research team (l-r) Zac Tait, Jens Nejstgaard, Marc Frischer and Stella Berger

“What’s happening with climate warming is not only are we increasing temperature, we are also increasing the carbon dioxide (CO2)which has the effect of acidifying the ocean – just like a can of cola,” said Frischer. “In this experiment we are studying not just temperature or acidity individually, but their combined synergistic effects”.

What makes it so complicated to study is that there are many different organisms interacting with each other, and at the same time reacting differently to the climate change.

“So instead of just picking out a few organisms to look at in the laboratory, we have to investigate large representative pieces of the ecosystems to tell what effect the climate changes will have on the environment,” said Nejstgaard.

The experiment was conducted at a mesocosm facility of the University of Bergen. There, the scientists could enclose two and a half cubic meters of natural seawater in each of 14 tanks, recreating an ecosystem with all the biological and chemical components that exist in the natural water column. They are called mesocosms because they represent intermediate systems that are bigger than a laboratory test tube but smaller than the ocean. The researchers changed the temperature and CO2concentrations in the mesocosms, and then observed how the various parts of the ecosystem reacted.

The Bergen mesocosm facility

“Mesocosms provide the opportunity to conduct controlled experiments that are impossible to do either directly in the ocean or in the laboratory,” said Nejstgaard.

The team also added a third factor to the experiment. Gelatinous organisms are an important part of the oceanic ecosystem, but typically they are fragile and do not survive the process of pumping seawater into the mesocosm tanks. In order to more closely mimic the natural marine environment, the researchers added tiny gelatinous organisms called appendicularians as representative “jellyfish” to the tanks after they were filled.

The Bergen mesocosm facility is the longest continuously operating mesocosm facility in the world. It has run for 33 years and Nejstgaard has led international experiments there for the two last decades.

Since 2009, Nejstgaard has directed the first European coordination of mesocosm facilities, MESOAQUA (http://mesoaqua.eu/), together with Berger as a scientific coordinator. Although Nejstgaard relinquished his position in Bergen in order to join the faculty of the Skidaway Institute of Oceanography in January 2011, Berger maintains a part time position in the MESOAQUA program. Frischer and other Skidaway Institute scientists have been collaborating with the Bergen facility for more than a decade. This was their fifth experiment there.

The funding for this experiment was complicated. Both American and European scientists applied for research grants. The Europeans got their funding; the Americans did not. The funding came from the Norwegian Research Council, the Nordic Council of Ministers (NordForsk) and MESOAQUA. Luckily two of the three European grants provided some travel support for non-Europeans, making it possible for the Skidaway team to participate.

Although the team was international, the original design for the project came from a small group including Frischer, Nejstgaard and Norwegian colleagues. Their primary focus was on the effect ongoing changes would have on oceanic bacteria. Very preliminary results look good for bacteria, but not so much for the rest of the marine ecosystem.

“Our preliminary data suggests that rising acidity increases bacterial activity, which has some profound implications on how the ocean is going to change,” Frischer said. “If conditions favor the growth of more bacteria, they will benefit at the expense of other types of microscopic marine life, particularly marine algae like phytoplankton.”

Phytoplankton are a major part of the bottom of the food web. Their productivity has a direct effect on the food supply for microscopic animals (zooplankton) and all larger marine animals. On the other hand, energy that goes into the bacteria is believed to just cycle among very small organisms that are hard for the larger organisms to eat. If that is so, the global warming spell even more problems for the ocean’s already troubled fisheries.

“When you start looking at how all the little pieces are connected, those insights we gain will help us understand how our planet will change and what that will mean,” Frischer concluded. “That is what we are trying to learn and it is important to every aspect of our society.”

Since it is important to investigate the effect of environmental changes on different natural communities, the Skidaway Institute team hopes to be able to obtain funding to continue experiments in Bergen, and elsewhere, including in our own backyard.

“We hope to develop a world-class mesocosm research center at the Skidaway Institute of Oceanography where we believe the potential exists for the Institute to become a leading facility for the region,” said Nejstgaard. “Such a center would contribute to future studies of the many environmental challenges that face our region.”

Skidaway Institute seeking ‘citizen scientists’ to assist with salt marsh study

February 11, 2011

Skidaway Institute of Oceanography professor Clark Alexander is looking for volunteer scientists to help him assess the problem of marsh wrack.

Marsh wrack is the dead marsh grass that forms large layers on top of the water or the marsh surface. Alexander is seeking volunteers willing to identify and photograph sites where wrack accumulates on at least a weekly basis throughout 2011.

Marsh wrack on Skidaway Island

As part of a grant funded by the Coastal Zone Management program, Alexander is working to assess the distribution and persistence of wrack in salt marshes throughout coastal Georgia. He and his team are using aerial photography to determine how much wrack is present in coastal Georgia and where wrack is found in different seasons.

“One additional issue that we want to address is how long wrack persists in a variety of marsh settings,” said Alexander. “To do that, we want to enlist the interested public to help us in documenting marsh wrack sites.”

The first step for any interested volunteers is to identify a site they are willing to photograph on at least a weekly basis.

“If you have a site you know accumulates wrack each year, but which has not accumulated any yet, you can monitor it for this project,” said Alexander. “Just start taking pictures right away so that we will have documentation of when it accumulates.”

Volunteers should have access to a digital camera and an email account, but no other specialized equipment is required.

Interested volunteers should send an email to Alexander at clark.alexander@skio.usg.edu.  He will provide a specific set of instructions.

Skidaway scientists map salt marshes topography with a view from above

August 26, 2010

Salt marshes are among the world’s most valuable ecosystems. They treat waste, provide habitat for marine life, produce food and offer recreation. They are also our key natural defence in the face of climate change and sea level rise. These services are driven by the fact that twice everyday, marshes are submerged by the flooding tide and six hours later, drained by the ebbing tide.

Skidaway Institute professor Jack Blanton and two visiting scientists from the University of Lisbon (Portugal), Francisco Andrade and Adelaide Ferreira, are contributing to the understanding of  salt marshes by using aerial surveys to improve the way they are mapped. Research associates from Skidaway Institute, Julie Amft and Mike Robinson, are also participating in the project.

(l-r) Francisco Andrade, Jack Blanton and Adelaide Ferreira

“We all have seen how the tide flows through the meandering network of salt marsh channels, but it is virtually impossible to go in the salt marsh and accurately map the entire channel network and the surrounding vegetated areas,” said Andrade.

Most charts simply show a salt marsh as a flat surface, cut by channels where boats can navigate. However, it is critical for scientists to understand how the marsh functions and evolves.

“To understand a salt marsh, we must know how much estuary-water the tide moves over it together with how the water spreads over the salt marsh and how it retreats,” Andrade said.

The scientists have developed a method that relies on identifying the flooded area of a salt marsh at any given moment using an infrared (IR) aerial photograph. Since IR light is almost completely absorbed by water, the flooded areas show up as dark, as opposed to brighter dry areas. The active green vegetation, whose chlorophyll strongly reflects IR, will show brighter shades. By taking a series of aerial photographs during the course of a tidal cycle, and coupling each corresponding flooded area to elevation data from local tide gauges, scientists can develop a topographical profile of the marsh.

In the left hand image, the digital elevation model for the Duplin River and surrounding marsh. The area in the red box is enlarged in the right hand image.

The team tested their technique in the Duplin estuary, behind Sapelo Island, Ga., by constructing a detailed digital elevation model (DEM) of the entire intertidal area, including all the salt marsh.

“Using the DEM, circulation patterns over the intertidal area and the corresponding water volumes can now be readily evaluated, yielding information on the time material is retained in the marsh,” said Blanton. “Moreover, the high-resolution DEM provides detailed topography required for state-of-the-art hydrodynamic circulation models whose goal is to faithfully represent currents in the tidal channels and over the surrounding intertidal area.”

The scientists are currently testing their new technique by comparing their results with independently measured topographical data. Plans are underway to conduct an additional survey on an ebbing tide. The rate at which the marsh floods compared to the rate at which it ebbs will provide quantitative estimates of water retention as well as ground water discharge.