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Stomachs, Ear Bones and Electrofishing: Dissecting the Invaders

Friday, June 28th, 2013

By Katie Sinclair

SERCterms Mark and Brooke weigh and measure a bluecatfish.

SERC interns Mark and Brooke weigh and measure a blue catfish.

Ever wonder what a catfish eats? The blue catfish, invasive to the Chesapeake, is not a picky eater.

This voracious predator eats pretty much anything that can fit in its mouth.  By digging into their stomachs, a process vaguely reminiscent of high school biology classes, researchers can figure out the impact this species has on the ecosystem.

 In order to get some fresh catfish stomachs, researchers working in the Fish and Invertebrate Lab at SERC set up a “Gon’ fishing” sign and hit the field.

 Using a technique known as “electrofishing,” researchers stun the fish with electric currents in the water and collect them from several sites along the Chesapeake and rivers that feed into the Bay. Once the fish are caught, they place them into a cooler. The frozen fish are then identified by species, weighed and measured. Each fish varies tremendously: From a few ounces to over 10 lbs., a wide range of maturities and sizes are represented.

Paige and Mike begin to dissect the fish.

Paige and Mike begin to dissect the fish.

 A closer look at the stomach

A closer look at the stomach

The ecologists then remove the fish’s stomach,  taking great care to keep it intact. (Though frozen, the contents of a fish’s lower intestines tend to have a rather unpleasant smell). As fishermen know, gutting catfish can get messy, especially when the interns get involved.

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Marsh Rovers: Research at the SERC Marsh

Thursday, June 27th, 2013

By Katie Sinclair

If you take a stroll out along the green grated catwalk that lies several feet above the muddy marsh ground at SERC, the first thing you’ll notice is strange white structures dotting the lush landscape. No, the aliens haven’t landed. These white enclosures make up several experiments at SERC. The goal of each experiment is to determine how a changing climate will affect this valuable marsh habitat, which stores carbon, has high primary productivity, and provides homes for fish, crustaceans, insects,  and more.

The SERC marsh. Under each treatment, conditions are set to mimic the CO2 concentration expected in 2100. (Credit: Thomas Mozdzer)

The SERC marsh. Under each capsule, conditions are set to mimic the CO2 concentration expected in 2100.
( Thomas Mozdzer)

Carbon and Nitrogen: Elements of Growth

Since 1987, SERC scientists have been pumping CO2 into these plastic chambers to simulate the marsh a century from now—a marsh in the grip of climate change. Inside these miniature time capsules, marsh plants grow with 350 parts per million more CO2 than is in the atmosphere today, levels scientists expect to see by the year 2100.  As marsh plants grow, they take in CO2 from the air. This carbon can either end up sequestered in the soil or released back into the ecosystem through decomposition. The CO2 addition experiments conducted at SERC are the longest-running in the world.

Besides carbon, marshes also rely on nitrogen, an element necessary for the creation of proteins. Due to runoff from fertilizers, nitrogen levels are also increasing in estuaries like the Cheasapeake Bay. As the concentration of both CO2 and nitrogen increases, scientists at SERC are asking important questions about how the structure of the marsh will be affected, including how it will change the plant communities that will grow there.

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From the Field: Sleepless Nights and Road Trips

Tuesday, June 25th, 2013

by Cora Johnston

When studying major ecological changes, like the movement of entire species or ecosystems, we often have to sample across large geographic areas. This means lots of road trips!

Taking a moment to reflect after a field day that started at midnight. (Cora Johnston)

Taking a moment to reflect after a field day that started at midnight. (Cora Johnston)

Starting nearly two months ago, I began my own road trips along the coast to survey the larval crabs that are washing ashore in swarms. Crabs typically recruit (leave the open ocean as larvae to join adult populations in coastal habitats) in a few brief but frenzied weeks in late spring and early fall. Therefore, I’ve been busy hopping between sites to gather as much data as I can while the crabs are abundant. Unfortunately, this means that my schedule, like the crabs’, depends on moonlight and tides. I’ll wake up around midnight, drive until the wee hours of the morning, and then sample the incoming tides by moonlight until wrapping up and moving to my next site as the sun rises. I then load up a kayak and spend the day paddling around collecting larger crabs (though still far too tiny to eat) from deep in each habitat to compare to the larvae I find riding the currents at night.

I head off on these adventures wielding stacks of audiobooks, a hefty thermos and lots of pre-labeled jars and data sheets that ease the demands on a weary mind. I munch trail mix to battle the exhaustion and swim to soothe the bug bites. After a few weeks on this schedule, even I find it hard to believe that I will get up at midnight the very next week to start all over again. Luckily, what keeps me coming back is what got me out of bed to do these studies in the first place.

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From the Field: Sea Wall Scraping Round II

Wednesday, June 19th, 2013

by Katrina Lohan

Sherry Reed (in pink) and Kristina Hill pick through clumps of oysters removed from the seawall at the Harbor Branch Oceanographic Institute. (Katrina Lohan)

Sherry Reed (in pink) and Kristina Hill pick through clumps of oysters removed from the seawall at the Harbor Branch Oceanographic Institute. (Katrina Lohan)

For our final sampling location we chose another seawall, at the marina at the Harbor Branch Oceanographic Institute. I had never been there before and the campus is beautiful! Driving into the marina from the Indian River Lagoon, the inlet is lined with mature mangrove trees, which also surround the entire marina. It was fairly windy that day, so the ride over was choppy, but once inside the inlet, the water was calm and the breeze was almost indiscernible.

It was my job to hold the boat against the seawall while Kristy and Sherry hammered oysters off the wall. I also kept track as they called out numbers of Ostrea sp.—we didn’t bother counting Crassostrea virginica because they were everywhere! Unfortunately for us, there were no Isognomon sp. along the wall, which we all found odd given that this habitat was so similar to the seawall we had previously sampled, where we found that species.

After about an hour of sampling, we were all wishing for the breeze! Without that breeze, the sun intensity felt more brutal and it was stiflingly hot. Once we had enough C. virginica and Ostrea sp. we drove around to a few other spots within that inlet to see if the Isognomon sp. were more localized, but no luck. I wanted another sediment sample from this site, but it was too deep along the wall, so Sherry found a spot in the mangroves that wasn’t too dense. I hopped out of the boat and took my sediment and water samples. I started looking for Isognomon sp. on the mangrove branches, but only found a handful… We had one last look on the rocks on our way out of the inlet, but no luck there either. Bummer! Well, two out of three species isn’t too bad!

From the Field: A Day Off?

Tuesday, June 18th, 2013

by Katrina Lohan

When Kristy and I go on these sampling excursions, we generally pack in a lot of sampling and processing into a short amount of time. We work every day, including weekends, and average 11-12 hour workdays for the two-week timeframe. So you can imagine our surprise when we finished processing all of the oysters from the second sampling location and realized that we had time in this trip for a day off!

What do two marine biologists do on their day off in Florida? Go to the beach! We inquired with the local staff as to the best place to go and were told that the Florida Inlet State Park beach was preferred as they had bathrooms and showers. We took the advice and headed to the beach for a day of R&R. I realized while sitting on the beach, mesmerized by the pounding of the waves, that it doesn’t take much for me to remember why I wanted to be a marine biologist. I am still awed by the power of water, watching the waves roll into the shore, crest, then fall, pounding into the sand and churning the shell fragments, turning them into smaller and smaller bits. I still stare at the ocean with wonder, imagining the vast and curious creatures that live in a world so completely different from the one that is familiar to me. Having these moments helps me to rejuvenate, so I can get back in the lab, continue processing my samples, and, hopefully, add to the body of knowledge about the ecology and evolution of marine creatures.

From the Field: Oyster Parasites Through a Microscope

Thursday, June 13th, 2013

by Katrina Lohan

Microscopic cysts inside a Crassostrea virginica oyster. (Katrina Lohan)

Microscopic cysts inside a Crassostrea virginica oyster. (Katrina Lohan)

In addition to taking oyster tissue to test for the presence of protistan parasites, we are also analyzing the oyster tissue for larger, but still microscopic, parasitic species such as worms, trematodes, and copepods. We have found parasites in all the species examined in all the locations we have traveled, but I got the best pictures of critters observed in oysters in Florida!

The highest prevalence and density of parasites occurred in Crassostrea virginica oysters. So far, I have seen copepods, turbellarians (probably Urostoma sp.), pea crabs, gill parasites, and cysts (probably from cestodes). I even saw what looked like a fish embryo, which was probably just brought into the gills, and an insect larva. Seeing all these critters under the microscope has made me contemplate why oysters are considered an aphrodisiac!

From the Field: Sea Wall Scraping

Wednesday, June 12th, 2013

by Katrina Lohan

Sea wall coated with oysters at South Bridge Marina. (Kristina Hill)

Sea wall coated with oysters at South Bridge Marina. (Kristina Hill)

Our second sampling location was a sea wall adjacent to a marina just below the south bridge in Ft. Pierce. The water was shallow enough along the wall that we were able to get out of the boat and stand in front of the wall, which made hammering and scraping the oysters off of it much easier!

Just as before, finding enough Crassostrea virginica oysters was easy, but finding the other oysters…took a lot more scraping. The Isognomon sp. at this location were fairly small and tucked into the crevices created by C. virginica, so they could be harder to spot. I took a step-wise approach, collecting the easiest species first, then making sure I had enough Isognomon sp., and only then did I move on and attempt to locate Ostrea sp., which easily took up the majority of our time. Most of the individuals in this species were dime-sized or smaller, tucked into the crevices or even in the dead shells of other oyster species, and they were covered in turf algae and mud. It took me (and the others) about an hour to find a sufficient number of these little guys at each of our respective sampling sites along the wall.

The funniest part of sampling along this wall was that there were lots of people around who did not hesitate to yell out! I am grateful to the multiple individuals who were concerned for our safety and mentioned the pilings in the water near the wall. (The water was clear enough to see them and we walked very slowly. Also, we all wore hard-bottomed water shoes and thick gloves.) We also had multiple boaters that were traveling in and out of the marina ask what we were doing, though I think some of them probably thought that we were just there to clean off the seawall!

Once all the oysters were collected, I took one water and one subtidal sediment sample and put them on ice. Then it was back to the lab to process more oysters.

From the Field: Dolphins!

Tuesday, June 4th, 2013

by Katrina Lohan

 A dolphin surfaces in Indian River Lagoon, Fla. (Kristina Hill)

A dolphin surfaces in Indian River Lagoon, Fla. (Kristina Hill)

We soon learned that it is mating season for dolphins and they frequently visit the Indian River Lagoon. On our boat trips to sampling locations, we have seen dolphins twice, and both times they were engaging in courtship behaviors. They are such graceful creatures.

I have to admit that I really, really want to see a manatee, another commonly spotted marine mammal in the lagoon. I haven’t spotted one yet, but I’m keeping my fingers crossed!

More on dolphin courtship >>

View manatee spotted in Florida mangroves >>

From the Field: Biofilms and Sediments

Monday, June 3rd, 2013

by Katrina Lohan

Kristy Hill uses cable ties to secure  a "biofilm collector" (a.k.a. microscope slides in a container) to a cage suspended from a local dock. (Katrina Lohan)

Kristy Hill uses cable ties to secure a “biofilm collector” (a.k.a. microscope slides in a container) to a cage suspended from a local dock. (Katrina Lohan)

As you may recall from a previous blog, part of the research for my fellowship project involves using genetic tools to look for parasites outside of their host organism in order to increase our understanding of the general ecology of these parasites.

I have been collecting water samples at all of the oyster sampling locations, but I decided that I wanted a larger diversity of habitat types. Thus, after discussing this idea with my advisors, I have decided to also sample subtidal marine sediments at the oyster sampling locations and collect biofilm samples. I will use the same genetic techniques on all the sample types to examine the diversity and distribution of marine parasites associated with the different habitats.

To collect the biofilm samples, we are using microscope slides, which were secured into a slide holder and suspended off of a local dock. The plan is to them scrape the biofilm off the microscope slides at scheduled intervals during our trip. I can’t wait to see what’s growing on them in a few days!

Read more on parasites surviving in disease reservoirs >>

From the Field: Parasite Hunting in Florida

Friday, May 31st, 2013

by Katrina Lohan

Jack's Island oyster reef in Indian River Lagoon, Fla. (Katrina Lohan)

Jack’s Island oyster reef in Indian River Lagoon, Fla. (Katrina Lohan)

For our next parasite hunting adventure, Kristy and I will be spending two weeks on Florida’s Atlantic Coast at the Smithsonian Marine Station at Fort Pierce. The marine station is located on a beautiful lagoon. We arrived on Monday and got a warm welcome from the staff, a thorough tour of the facilities and unpacked all of our gear, all four boxes of it. (No, we don’t travel light!) While here, we are staying on campus at the Taylor house, which is a residence for visiting scientists complete with kitchen, full bathroom, and a beautiful wrap-around porch that faces the water. We have long days and nights on these field trips, so it’s nice to have close accommodations that allow us to easily get back and forth to the lab, along with a full kitchen so we can cook quick and easy meals before returning to processing oysters. So far, I’m impressed!

On Tuesday, we headed out to our first field location. We hopped in a small boat owned by the Smithsonian and went to Jack’s Island, an oyster reef surrounded by mangrove trees. We were able to easily find Crassostrea virginica, as it is the species that makes up the reef, and then had to spend a little more time searching for Isognomon sp. at each site to get the numbers we needed. Also, it’s virtually impossible to tell which oysters are Ostrea sp. without opening the shells, so hopefully we have enough of those….

We also had a new first at this site—this is the first time that we have had a tour boat pass us while we were collecting!

Read accounts of marine biologists hunting for oyster parasites in Panama >>