Hurricane Dorian

Last week Hurricane Dorian impacted North Carolina.  In collaboration with the MARS Lab at Duke University, including Justin Ridge, we examined how the storm affected the morphology of Bird Shoal.  Before the storm came by, we deployed a camera trap and imaged the island with an eBee drone.  Above is an example of what it was like on the island during the Hurricane.  The worst of the storm hit during the night and could not be recorded.  Bird Shoal provides the town of Beaufort protection from storm waves.

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The first oyster

I’ve been working with Molly Bost to compare oyster reef growth and composition among tidal and landscape settings.  Our data set is composed of 12 natural reefs and this week we sampled the first oyster to colonize each reef to learn how old they are.  That oyster is identified by taking a core through the living reef and sifting through shells at the base of the reef to find an intact oyster (both valves).  We send a piece of that shell to NOSAMS for radiocarbon dating.  The oldest living reef we have sampled so far is about 900 years and the thickness of that reef was 1.15 m.  We have other reefs in our study that are twice as thick.  Earlier this week I read in EOS that a 2,674-year old North Carolina Bald Cypress Tree was discovered in the Black River.  Perhaps some of our oyster reefs are older than that nearby Cypress Tree?

That first oyster to grow in the area, sampled at the base of the reef, was a true visionary.  It probably never expected a reef like the one shown below would form on top of it. It belongs in a museum, but will be converted into carbon dioxide instead. It just keeps giving.

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IE 2018 Field Trip to Cheeseman Inlet

This post is to help the IE 2018 class prepare for their first exam.  It’s been a tough semester filled with large storms, evacuations, and modifications.  I thought this information would be helpful because when classes are on a field trip experiencing the beauty of the NC coast and the natural environment, it can be difficult to remember the lessons learned and the context of the observations made.  We visited two saltmarsh sites at Cheeseman Inlet, an ephemeral flood-tidal delta that formed about 200 years ago in Bogue Sound.  Watch the movie and look at the cores from both sites to help you remember the marshes we observed and what that means in terms of sea-level rise and changing environments through time.

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Backpack Vibracore

We have a project looking at salt-marsh trangression and some of our site locations are composed of wide fringing salt marsh; difficult to access.  Our new favorite coring device is the backpack vibracorer.  I don’t think we could have collected core transects across 100-m wide salt marshes without this tool.  It’s lighter than our standard vibracorer and just as powerful.  We can easily hike into difficult terrain and collect the cores we need from the shoreline to the upland boundary.  If only pulling the cores out were as easy as driving them down.  If you have the means, I highly recommend picking one up.

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East meets West

The past two days we have been field tripping with Chuck Nittrouer’s class from the University of Washington.  They are a great group of students, post-docs and visiting professors all smart, personable, and fun to be around.  Emily Eidam, Nittrouer lab alum and new faculty at UNC Marine Sciences was also part of the group.  We spent one rainy day on the Newport River and Bogue Banks (it was actually a gale) and one beautiful day on Shackleford Banks.

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Spring Semester 2018

It’s been a fun spring semester.  Brent McKee and I have been leading two seminar classes at Chapel Hill.  One looks at sediment accretion in North American estuaries across the Anthropocene and the other is more broad, titled Frontiers in Marine Geology.  Carson Miller, Molly Bost and I presented research at the Ocean Sciences meeting in Portland Oregon.  We also had time to explore the surrounding geology.

Getting to know the rocky intertidal along the Oregon coast.

In March Molly, Carson and I collected some Chirp sonar data in Jordan Lake, NC.  This reservoir has some problems with water quality and perhaps resuspension of bottom sediment is contributing to the poor water quality.  We are mapping sediment thickness to identify the best spots for sampling.

Jordan Lake is a beautiful recreation area.

Towing the Chirp tow fish. It’s important to collect data close to markers, even if they are labeled “Danger”.

Charlie Deaton and Anna Atencio just submitted their theses to the graduate school.  That was the last hoop to jump through.  Both will soon have Master’s degrees from UNC.  Great job.

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Coastal Geology Club

We don’t have an official Coastal Geology Club at IMS, but during our open house in Oct. 2017 there was a lot of interest in starting one.  People from all over eastern Morehead City were enthusiastic about making ID cards and learning about the geology of the area.  If we move forward with a local Coastal Geology Club, Marie Tharp will be our inspiration and everyone will be invited to join.

Geo Club ID cards

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Salt marsh transgression by Carson Miller

Methods, methods, methods was the key focus this summer for my project. My project aims to understand how different salt marsh – upland morphologies affect salt marsh transgression (landward movement) with physical factors like increasing rates sea-level rise and frequency of large storms.

I used to really hate reading the methods section of papers because they didn’t always make complete sense to me and I didn’t find them particularly thought-provoking. However, this semester I started to learn through a seminar class that I’m taking that methods really determine the validity of your science. For example, we read a paper where the authors used an age date from an axe found in a UK marsh, which really made us question how valid that date really was (how old was the axe when it was lost and the tree before the axe was made?). So, this summer we set out to solidify the methods that we were going to use for my project.

Carson, Molly and Tony (left to right) resting half-way through the marsh march.

We went to Cedar Island and trekked through a quarter-mile of Juncus romarianus marsh. As Molly describes it, it’s type two fun where it’s not really that fun in the moment but when you get back you only remember it as being a fun day with friends and colleagues. To give you some insight into how this day went, a quarter-mile doesn’t sound very far, but when you’re walking through the thickest Juncus you’ve ever seen in your life a quarter-mile seems like a marathon. Juncus is a super robust marsh plant that is tall and almost woody.  It tapers off at the top (about eye-level) to a point that can and will puncture your skin. The goal of the day was to determine the depth of the contact between marsh sediment and upland soil. Unfortunately for us, that contact was not quite clear in the sediment.

This is what we thought the contact would look like…a color change.

This is what the contact between freshwater peat and saltwater peat looks like.

This is where we had to reevaluate our methods so that we could find a valid way to determine the contact between saltmarsh peat and freshwater peat. So, we headed back to the lab in search of a new way to verify the marsh-upland contact. I spent the next few weeks digging through the sediment, meticulously washing it, but very carefully to look for tiny creatures called foraminifera. Foraminifera are calcium-carbonate based creatures that only live in the water. Scientists have used foraminifera for years to try to build sea-level curves and determine past climate history. For us we were more interested in the presence versus absence of foraminifera because we wanted to use them to look down core and find the precise contact for the marsh-upland boundary. We can use this approach because foraminifera live in the marsh, but can only be transported into the upland through very high tide events, or storms. The difficult part of this was looking down a microscope for many hours a day, but also there was so much organic material blocking my view. Because foraminifera are delicate you can’t burn off the organic because the creatures fall apart. Instead, we used another approach where we tried to digest the organic material with hydrogen peroxide, but that didn’t work either because we ended up losing the forams along with only a portion of the organics.  In the end we found simply isolating the finer particles with sieves and using a sample splitter on the remaining fraction was the best approach.



Microscope view of a sample. Notice the foram in the center.

Through all the failures this summer we had one major success.  We determined that you can indeed use foraminifera to determine the contact between marsh and upland, and you can do it very precisely based on how many segments you cut your core into. We sectioned ours at 1-cm increments, so we were able to determine that contact at a centimeter precision.  Even though I read many papers that used different methods for separating foraminifera from saltmarsh peat it’s important to try methods out on preliminary samples before collecting a complete dataset.

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New Lab Mates = New Projects

Welcome Carson Miller, Molly Bost and Jessie Straub.  The Rodriguez Lab is not new to Carson and Molly, but Jessie comes from Coastal Carolina University, and it took her about 10 minutes to settle in and feel like a lab mate.  Carson wants to study salt marsh transgression, Jessie is interested in coastal hazards as they relate to dune erosion, and if you don’t know Molly, she is excited about everything that has to do with sediments.  This is the first week of classes at UNC and we miss the summer terribly.

Still happy after a long hike through the marsh and poison ivy.

Installing sensors on Shackleford Banks.

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Processing Oyster-Reef Cores

Oyster reefs are often the only natural hard substrate in estuaries and are even labeled “oyster rock” on many old nautical charts.  Oyster reefs have the potential to grow extremely rapidly (10 cm/year); in comparison, coral-reef growth, is measured in mm/year.  Oyster reefs are not only composed of oyster shells, they have an abundance of mud and organic carbon filling pore spaces between shells.  A core through an oyster reef samples compositional changes through time, but extracting that record is tedious.  In this time-lapse video, Rachel Quindlen, Molly Bost, and Carson Miller are subsampling an oyster-reef core.  The constituents of every 5-cm long subsample are separated using a sieve and later by combusting organic matter and measuring particle size with a laser.  It’s time-consuming, but worth it.

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