by Katrina LohanJust as in previous trips, part of our sampling involved dissecting the bivalves and preparing tissue preps to view under the microscope. I have to admit that the microscopic metazoan parasites that I saw on this trip were not quite as exciting as previous trips—I miss the really cute turbellarians (a.k.a. Urostoma sp.)! Though they weren’t as cute, I did see some parasites through the microscope, including trematode metacercariae in the mussels, three marine mites, a handful of pea crabs and free-swimming harpacticoid copepods. I had never seen a marine mite before and at first thought there were ticks running around the lab. That’s what happens when you spend hours in front of a microscope–you forget how small the things you are viewing actually are!
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by Katrina Lohan
If you have ever tried to open M. mercenaria, then you can fully appreciate that the folks at the ESL gave us a specially designed apparatus just for shucking clams. Even then, the clams we collected were pretty big, so getting them open was really hard.
A co-worker from the Marine Invasions Lab, Michele Repetto, joined Kristy and I on this trip and she has become a master shucker. Between Kristy and Michele’s excellent shucking capabilities, the large clams didn’t stand a chance. Now the mussels on the other hand presented a separate challenge, which was attempting to get them open without destroying the shells, which we are archiving and will eventually submit to the molluscan collection at the National Museum of Natural History.
While I frequently broke the mussel shells into many pieces, Kristy and Michele had the appropriate finesse to open the mussels without causing massive shell damage. Have to enjoy the challenges of working with different species!
by Katrina Lohan
The end of our field season (if you call half a year a field “season”) is coming to an end as we now head for our sampling location in the Chesapeake Bay. Our northernmost sampling location is Wachapreague, Va., located on the Delmarva Peninsula and home of the Eastern Shore Laboratory (ESL) of the Virginia Institute of Marine Science (VIMS).
Kristy and I are both alumnae of the College of William and Mary and conducted our graduate research at VIMS. For my Ph.D., all of my fieldwork was conducted at the ESL, so returning as a postdoc, working on a different disease system, is a little surreal for me. It has been nice to catch up with the folks at this lab and see the new buildings, which were still in preparation when I graduated. How time flies!
Before venturing out on this particular trip, we contacted our collaborator Ryan Carnegie of the Shellfish Pathology Lab at the Virginia Institute of Marine Science to get some suggestions about sampling location. He suggested sampling oyster reefs at Mockhorn Channel just off Oyster, Va., as they had historical data from that area. The folks at the ESL knew just where to take us and we headed out on Tuesday to collect.
In previous locations we aimed to collect three oyster species. However, there is only one oyster in the Chesapeake Bay: Crassostrea virginica, the eastern oyster. So we decided to collect other bivalves: the ribbed mussel (Geukensia demissa) and the hard clam (Mercenaria mercenaria).
Our boat captain, Edward Smith, suggested that we split up so that we could complete the collection prior to the tide coming in. I ended up on the high marsh searching for mussels, which was super muddy and, consequently, lots of fun! It was beautiful weather and just windy enough that the bugs stayed away. Once all the mussels and oysters were collected, we all headed to a mud flat to rake for clams. I have to admit that I am horrible at finding clams. While Edward found more than 30 clams, I found three….Good thing that others were better than me or we would never have found enough. Then it was back to the lab to figure out how to shuck them all!
By Katie Sinclair
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.
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.
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.
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.
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!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.
by Katrina LohanFor 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!
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.
by Katrina LohanIn 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!
by Katrina LohanOur 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.