Archive for November, 2013

Skidaway Institute scientists study black gill in shrimp

November 25, 2013

Scientists at the University of Georgia Skidaway Institute of Oceanography are investigating black gill in shrimp, a condition Georgia shrimpers are blaming for an ongoing downturn in shrimp harvests. Very little is known about black gill, so professors Marc Frischer and Dick Lee are working with shrimpers and a number of agencies in a collaborative project to answer some key questions about the condition.

R/V Savannah crewman Chris Keene prepares to dump a load of shrimp and other marine life for inspection and study.

R/V Savannah crewman Chris Keene prepares to dump a load of shrimp and other marine life for inspection and study.

 Black gill is a symptom of a health problem in the shrimp. The affected shrimp are easy to identify because they exhibit large black areas on their gills, which are right behind their head. The black gill has no effect on the edible qualities of the shrimp. Shrimp affected with black gill are perfectly safe to eat, and the condition has no effect on the taste of the shrimp.

 Black gill has been an issue for pond-raised shrimp for more than a decade, but it has only been within the last several years it has become a problem for wild shrimp fishermen. Black gill can be triggered by several factors among pond-raised shrimp. Skidaway researchers believe black gill in wild Georgia shrimp is caused by a microscopic parasite classified as a ciliate—a single cell animal with tiny hairs called cilia that help them move. The scientists don’t know yet exactly which ciliate is to blame. The blackened gills are the result of the shrimp’s immune system reacting to the ciliate invasion. It creates black nodules around the invasive ciliates in the shrimp’s gills.

Three shrimp with black gill.

Three shrimp with black gill.

 Beyond the blackened gills, it is not known how the condition affects the health and morbidity of the shrimp. Shrimp shed their gills through their normal molting process. Scientists suspect the parasite triggers a molting response, causing the shrimp to shed their shells and gills repeatedly in an effort to rid themselves of the parasite. This may cause them to use up extra energy and leave them stressed and vulnerable to predators. Examination of infected gill tissue also reveals the ciliate can damage the shrimp gill and directly impact the ability of the shrimp to breathe.

 The Georgia Department of Natural Resources statistics indicate that at its peak in October 2013, 40 percent of the shrimp captured in its surveys had black gill. Shrimpers are blaming black gill for reduced catches last year and so far this season.

 “That may turn out that is the case, or it may not,” said Frischer. “As of right now, we have no scientific evidence to support it. That would be a good question to address in an additional research project beyond this one.”

 Frischer, Lee and their collaborators will try to determine how black gill is transmitted, and if it is infectious. They also want to determine the distribution of the condition and its causative agent, and also see if the parasite exists in other crustaceans, in sediments or in the water.

 According to Frischer, the black gill ciliate may always be present in the shrimp and probably other places too. For most of the year, shrimp are able to handle it. “However, in the late summer the water warms and the oxygen level drops, the shrimp may become stressed,” he said. “This may stress the shrimp and allow the parasite to proliferate.”

 The two-year project will be sponsored by a $140,000 grant from Georgia Sea Grant, a unit of UGA Public Service and Outreach. The funding is not yet official, but Skidaway Institute scientists began their work early because this is the time of year when black gill is prevalent. 

 Anna Walker of Mercer University is working with the Skidaway Institute researchers to conduct pathological tissue studies.

 Other collaborators on the project include UGA Marine Extension Service, Georgia Department of Natural Resources – Coastal Resources Division, the Georgia Shrimp Association, the South Carolina Department of Natural Resources, Southern Shrimp Alliance, the Florida Fish and Wildlife Conservation Commission and the North Carolina Division of Marine Fisheries.


Fresh fish and dirty laundry

November 19, 2013

Skidawawy Institute Clifton Buck continues is account of his lengthy cruise across the South Pacific from Ecuador to Tahiti.

Ahoy There!

Current Position: S 15.75’ W 105.08’

It’s another Sunday at sea and we are transiting between Stations 15 and 16. Many in the science party use these 10-12 hour lulls in the action to catch up on sleep, update data logs, or continue their daily slog through the seemingly endless volume of samples. But for me, Sunday is laundry day (not all that different from at home in Savannah). Our ship has a laundry room, though no laundry service, and each compartment of cabins is assigned a particular day of the week for tending to dirty linens. The laundry is located deep within the bowels of the ship along with the food stores. Land lubbers may go queasy at the thought of folding their skivvies beneath the waterline but I find the sound of the waves breaking against the hull to be soothing to hear while I search for that missing sock.

Earlier today, we were treated to a lunch of freshly caught Mahi.

Ship’s oiler Orlando cleaning our catch.

Ship’s oiler Orlando cleaning our catch.

   Our usual operations do not allow for fishing but there are times the ship steams slowly enough to allow for trolling. Several members of the crew are avid anglers and are quick to deploy hand lines from the stern. It is a great treat for us when a fish is landed and one can imagine the joy preindustrial mariners must have felt at the prospect of fresh fish.

The internet has been filled with erroneous reports concerning the ongoing leak of radionuclides from the earthquake damaged Fukushima power plant. These reports suggest that contaminated waters and debris are spreading across the Pacific Ocean posing a threat to human health in the Americas. We are all exposed to naturally occurring radiation throughout our daily lives and seawater is chock full of naturally occurring radionuclides. While the area immediately surrounding the plant is grossly contaminated and radionuclides continue to seep from the site, there is no risk to us or anyone in North or South America. The radionuclides released in Japan are quickly diluted in the Pacific Ocean and are constantly disappearing due to radioactive decay. The Fukushima disaster has caused in an increase in radioactivity of about 25% above this natural background level in the near shore (~40km). At 600km from shore, the increase is only 2% above natural levels. In fact, there are several scientists from the Woods Hole Oceanographic Institution (WHOI) on board who were on the scene in Japan shortly after the earthquake struck. The risk of radiation exposure at their study site, just a few miles from the plant, was so low that no personal protective equipment was required whatsoever. Please visit WHOI’s Café Thorium website  for more information. So you can dig in to all of the sustainably caught seafood you like without fear of glowing in the dark!

Exit Challenge: Try to identify the seabirds in these photos. Post your answers in the comments.

Can you identify this seabird?

Can you identify this seabird?

What kind of bird am I?

What kind of bird am I?

More cruisin’ across the South Pacific

November 11, 2013

Skidaway Institute scientist Clifton Buck is on a lengthy research cruise in the South Pacific and is blogging about his experience.

Ahoy There!

Current Position: S 12 0.1067’ W 93 27.6890’

We are now a quarter of the way through our trip and the sun has finally begun to shine. The first two weeks were rather gloomy and downright chilly. While we are in the tropics, and you might expect hot and humid temperatures, the temperature near the South American coast is moderated by the cold water being brought to the surface by the upwelling action I described in a previous post. This is the same process that brings cold water to the California coast. Our cruise track has now brought us to the transition zone between the cold, coastal waters and the warmer waters of the subtropical gyre. Sea surface temperatures will now rise from about 17oC to a bath-like 28oC.gt13-cruisetrack 11082013

Days at sea are busy! With 32 scientists on board there is always someone working somewhere, 24 hours a day. And with an operating cost of $30,000 per day there can be no idle time for the ship. When we arrive on station work must begin whether it is 3:00AM or 3:00PM. That goes for Saturdays and Sundays as well; there are no weekends at sea. Some groups are fortunate to have enough personnel on board that they are able to split their work into 12 hour watches. However, most groups require everyone to be involved when conducting operations. And some groups are only one person, like me, and must be available at all times. This can lead to some very long days and nights.

With that said, a typical day starts at 7:00AM. Breakfast is served each day from 7:15 to 8:00. The cook staff, of which there are three, does an excellent job of providing a variety of foods at each meal and breakfast is no exception. Today there were huevos rancheros, blueberry pancakes, oatmeal, bacon, sausage, and pineapple coffeecake. And there are always self-service items like dry cereal, yogurt, and toast available. Most importantly, there are two coffee pots that must be full. On a ship, you live by the edict “You kill the Joe, you fill the Joe!”

Lunch and dinner are at 11:30 and 17:00. Both of these meals feature a salad bar which might be the best indicator for the length of time the ship has been at sea; let’s call it the vegetable index factor (VIF). At the start of the trip we are blessed with fresh veggies including green, leafy lettuce, tomatoes, avocados, spinach, mushrooms, and all the other produce you can imagine. As time goes by these items slowly disappear to be replaced by more hardy varieties. There are no markets in the middle of the Pacific and no resupply stops for us! In the last week we have seen the lettuce turn to Romaine, the spinach and avocados vanish, and the tomatoes change from plump cherries to larger (and less tasty) slicing types. Slowly but surely we will move from fresh fruits and vegetables to all canned and preserved. Yesterday we had the first appearance of the very sad canned mushroom. I’m not sure as to what the intended use of canned mushrooms could possibly be but they are without question a poor salad topping. Eventually we will be left with cabbage and all canned vegetables but that is in the future and like with any sad, inevitable reality I prefer not to dwell on it. In any case, both lunch and dinner are finished with dessert. Whether ice cream, cake, cookies, or pie there are always treats to challenge the waistline.

 We are now coming up on our eleventh station and will occupy this point for the next three days. We won’t have Internet because our antenna will not be able to “see” the satellite that keeps us connected to the outside world. It can be refreshing to go unplugged from all the noise on the web but I know that it does not just disappear. My Inbox will be flooded when we reconnect on Wednesday.

Thanks for reading!

News coverage on black gill research

November 4, 2013

We had some nice news coverage of our new research project looking into Black Gill Disease in shrimp. Mary Landers with the Savannah Morning News published this story last week.

That story was picked up by the Associated Press and was distributed to other outlets, including the ABC/FOX TV affiliate there in Savannah. Ashli Lincoln came out on Friday and produced this story.


Research cruising across the Pacific

November 4, 2013

UGA Skidaway Institute professor Cliff Buck is on a lengthy research cruise from Peru to Tahiti. Here is the second entry to is log of his experience.

Ahoy There!

Current Position: S 12.0449 W 77.3761

After 68 hours on location, we are finally leaving our first hydrographic station. A hydrographic station is a location that is chosen for intensive study. We will occupy 35 such stations over the course of the next two months and will use the data we collect at each to learn about the distributions of trace elements and isotopes (TEIs) in this region of the Pacific. We also measure basic parameters like temperature, conductivity/salinity, pressure, density, fluorescence and dissolved oxygen as these measurements can tell us about the movement of water masses within the ocean’s interior and help us interpret our chemical information.

We collect seawater and deploy sensors using plastic bottles mounted on a titanium frame called a rosette. The rosette is suspended from a sheathed Kevlar line which contains conducting wires that allow the transmission of signals between the surface and the rosette. In this way, we can monitor the depth of the bottles and can send them commands to close at specific depths. On this cruise, we are deploying a rosette able to hold 24 12-liter bottles, for a total of 288 liters of water on each cast

The GEOTRACES rosette being lowered over the side of the ship. The gray sampling bottles can be seen mounted on the titanium frame.

The GEOTRACES rosette being lowered over the side of the ship. The gray sampling bottles can be seen mounted on the titanium frame.

The entire package weighs approximately 1,600 pounds including the weight of the rosette, bottles, and sensors. The bottles are specially made of Teflon-lined plastic and contain no metal whatsoever to reduce the possibility that the sampling system will contaminate the seawater inside. The bottles can be detached from the rosette and carried into a clean sampling laboratory on board to reduce the possibility of contaminating the water inside. Once inside the lab, the water is filtered and stored in specially prepared plastic containers and bottles for either analysis on the ship or back on shore.

In addition to the rosette sampling system which brings seawater to the surface, a group of scientists from the Woods Hole Oceanographic Institution is deploying pumps that are able to operate to a depth of 5500 meters. These pumps are battery powered and are suspended from a wire lowered over the side. Their purpose is to filter 1200-1500 liters of seawater and to collect the microscopic particles which are present everywhere in the ocean. These particles have isotopic signatures that provide clues as to the circulation of the oceans and the rates at which particles sink from the surface ocean to the bottom. In the case of our first station, the bottom was 5500 meters (that’s 18,000 feet) beneath the ship’s keel.

My work, along with collaborators Dr. William Landing from Florida State University and Dr. Ana Aguilar-Islas of the University of Alaska – Fairbanks, is targeted on the input of TEIs to the surface of the ocean by atmospheric deposition. The atmosphere is full of small particles called aerosols which can include emissions from industrial processes as well as dust blown off of the continents. These particles can settle on the ocean’s surface by dry deposition or become incorporated into rain droplets and be scavenged from the atmosphere in wet deposition. We have installed four aerosol samplers on the highest deck of the ship which run vacuum motors pulling air through filters.

The four aerosol samplers can be seen in the foreground. The sampling filters are protected from sea spray and rain by the roof-like shrouds that give the samplers the appearance of birdhouses. The rain samplers are mounted in the background.

The four aerosol samplers can be seen in the foreground. The sampling filters are protected from sea spray and rain by the roof-like shrouds that give the samplers the appearance of birdhouses. The rain samplers are mounted in the background.

The aerosol particles are impacted onto these filters giving us a means to characterize their chemical composition and estimate deposition rates. We have also deployed two automated rain samplers which open and uncover their sampling buckets when their sensors detect rain. Any rain collected will be analyzed for a wide range of TEIs.

Taken together, these research programs will provide us with a better understanding of the chemical processes at work in the eastern Pacific Ocean.

For more information about Dr. Buck’s work, you can visit his Web page on the Skidaway Institute Web site.