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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Oyster Reefs Sometimes Can’t Keep Pace With SLR and Sedimentation

Seismic_CCB

Oyster reefs are similar to other carbonate depositional environment such as coral reefs.  The largest difference is that oyster reefs are located in estuaries and sediment loading from external sources, like rivers and shoreline erosion, is much higher than what corals experience.  Being filter feeders, oysters are designed for the estuarine environment and take advantage of the plentiful suspended matter in the water column.  However, too much of a good thing can be deathly.  Oyster reefs need to grow rapid enough so that they don’t become buried in sediment.  In most estuaries, sediment accretion matches the rate of sea-level rise (SLR), so if oyster reefs cannot grow more than 3 or 4 mm/year (the rate of SLR) they will cease to exist.  Above, is a seismic line from Nueces Bay, Texas.  Highlighted in blue is a large oyster reef, which kept pace with SLR and sediment accumulation (highlighted in those other colors), until it gave up and was buried by that most recent sedimentary unit shown in gray.  Why did the reef fall behind and give up all of a sudden?  Perhaps it became diseased or maybe sediment loading in the water column was just too much for the reef to handle?  Important questions to address if we want to improve conservation and restoration efforts.

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Dynamic barrier islands

During large storms, barrier islands are temporarily underwater because of storm surge and high waves.  This is called overwash, and during overwash sand is moved from the beach and deposited in back-barrier environments.  The sandy deposit that forms as a result of overwash is called a washover.  Below is an animation that shows the evolution of a washover (Site 2) on Onslow Beach, NC during a 4-year period.  Some of the most dramatic morphologic changes occurred after Hurricane Sandy and during a persistent nor’easter in October, 2015.  We are still working with these data, so stay tuned.

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Where has all of the time gone?

June: Collecting overhead photos with a toy drone.

June: Collecting overhead photos with a toy drone.

A bit of what we have been up to the past six months in photos.  We also worked inside many days, teaching classes and writing papers and proposals. It hasn’t been all fun and games, though.  A horrible summer in terms of funding, with all of our grant proposals being rejected (insert clip art here of man with pockets turned inside out).  On a positive note, Charlie Deaton joined the lab over the summer.  He is in many of the photos below.

June: Outreach activities.

June: Outreach activities.

June: Waiting for the interview to begin.

June: Waiting for the interview to begin.

 

June: Vibracoring old washovers at Onslow Beach.

July: Dune vegetation surveys with Barrier Island Geology and Ecology class.

July: Dune vegetation surveys with Barrier Island Geology and Ecology class.

July: Oyster reef research in Shallotte, NC

July: Oyster reef research in Shallotte, NC.

August: Lab hiking trip.  We started the hike at 4 and ended after dark...unforgettable, in a good way.

August: Lab hiking trip. We started after work and ended after dark…unforgettable, in a good way.

October: Testing out the BlueView sonar 3D scanner in the neighborhood pool.

October: Testing the BlueView sonar 3D scanner in the neighborhood pool.  Best place to learn how to use new gear.

 

September: Visiting oyster sills in the White Oak River Estuary, NC.

September: Visiting oyster sills in the White Oak River Estuary, NC.

August: Selecting a site to monitor marsh-shoreline movement.

August: Selecting a site to monitor marsh-shoreline movement.

August: Lots of samples were incinerated to measure loss on ignition.

August: Lots of samples were incinerated to measure loss on ignition.

October: Donuts go well with field work.  These were especially delicious.

October: Donuts go well with field work. These were especially delicious.

October: Documenting modifications to a washover fan.

October: Documenting modifications to a washover fan.

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