Student Research: Lost City

Did you know that there really is a lost city in the ocean? The Lost City hydrothermal vent field is a site of towering white chalk chimneys ranging from 65 to 200 feet tall located in the Atlantic Ocean, several kilometers away from the underwater mountain range known as the Mid-Atlantic ridge. Hydrothermal vents are underwater volcanoes on the seafloor where hot water that travels through the earth’s crust and gets heated, rises up and comes back out through the chimneys as extremely hot fluid, sometimes reaching temperatures over four times hotter than boiling water. The fluids that comes out of most hydrothermal vents are acidic and filled with elements such as iron and sulfur, giving it a smoky black appearance. At lower temperatures, vent fluids are a white-grey color.

Diagram of a hydrothermal vent field, from Wang et al. (2018), https://www.mdpi.com/2075-163X/8/11/512

On the other hand, the carbonate chimneys formed at Lost City are created through different processes and the resultant fluids are alkaline and have different components such as calcium and barium. Lost City hydrothermal fluids also have relatively low temperature, slightly below boiling. The rocks present beneath the seafloor at Lost City are different from those at other hydrothermal vents and they undergo a chemical reaction with the surrounding seawater, creating hydrogen and hydrocarbons, which microbes can use for food. This is essentially a free lunch for the microbes! Researchers study the microbes present at the Lost City as it is a site similar to ocean worlds found on other planets and moons such as Enceladus, which is one of Saturn’s moons, and Europa, one of Jupiter’s moons. The icy oceans present on these moons are hypothesized to support the same water-rock reactions. Therefore, from learning about the microbes present at Lost City, we can potentially learn about extraterrestrial microbes aka alien microbes!

Carbonate chimneys at the Lost City hydrothermal vent field in the Atlantic Ocean, from: https://www.smithsonianmag.com/science-nature/diving-deep-reveal-microbial-mysteries-lost-city-180970234/

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Featured image from: https://www.whoi.edu/know-your-ocean/ocean-topics/seafloor-below/hydrothermal-vents/

Script Author: Shu Ying Wee

Contributing Professor: Dr. Jason Sylvan

Student Research: Marine Aerosols

There is a lot of exciting oceanographic research being done at Texas A&M, over the next few weeks On the Ocean will be highlighting some of the work being done by graduate students in the department of oceanography.

https://planktonforhealth.co.uk/worlds-finest-marine-phytoplankton-powder/whats-definition-phytoplankton/

Phytoplankton are microscopic plants living in the ocean that photosynthesize, like trees, taking in carbon dioxide and producing oxygen. These tiny plants produce about half of the oxygen that we breathe and thus have a huge impact on our world. They also produce other substances that provide food for other marine organisms, making them an important part of the marine food web. These substances that phytoplankton produce are small enough that they could be lifted into the atmosphere as aerosol during wave breaking at the surface of the ocean. Marine sources of aerosol, like phytoplankton, represent a natural contribution to the atmosphere, which can also include dust and sea salt. However, non-natural sources due to human activity, such as air pollutants, are also important aerosol contributions. All sources of aerosols can form clouds under certain atmospheric conditions. The ocean covers about 70% of the Earth’s surface, representing a potentially large area for marine aerosol production which could cause changes in climate and weather patterns. However, we do not currently understand how it could affect Earth’s climate and whether it will cause increased or decreased global cloud coverage. Researchers in the Department of Oceanography and Atmospheric Sciences are working on a project studying different phytoplankton in laboratory experiments to better understand how different organisms and changing environmental conditions affect these atmospheric processes. The results from this study could provide fundamental information on how phytoplankton interact with the atmosphere and hopefully allow scientists to understand and predict the impacts of marine aerosol on the formation of clouds and Earth’s climate.

https://naames.larc.nasa.gov/science-objectives.html

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links please go to ocean.tamu.edu and click On the Ocean.

Featured image from: http://www.naturemuseum.org/the-museum/blog/how-do-clouds-float

Script Author: Alyssa Alsante

Contributing Professor: Dr. Daniel Thornton

Aquaculture: Barramundi

Barramundi, meaning “large-scaled fish”, is the name the Aboriginal people of Australia gave to Lates calcarifer. It is also know as the “passion fish”, a name derived from a folk story in which two young lovers, forbidden from being together by their tribe’s elders, run away and are hunted down by their tribes. The story ends with the two cornered lovers jumping into the sea and transforming into Barramundi, where they live to this day. The spines on the dorsal fin of the barramundi are said to be the spears hurled at the lovers by their tribes.

https://www.tnaqua.org/our-animals/fish/barramundi

Barramundi are catadromous, meaning, like the salmon, they live in both fresh and salt water throughout their lives. Unlike salmon, the barramundi returns to the sea to spawn instead of rivers. Barraundi have an elongate, laterally compressed body, with a pointed head, large scales, and a big mouth.

Diagram of Barramundi aquaculture stages, from http://www.fao.org/fi/figis/culturespecies/data/assets/images/lates/calcarifer-prdcycle.jpg

In Australia, Barramundi are an important commercial species, and a target of recreational fishers. They are well-suited to aquaculture, with a good tolerance for crowding and high production of eggs by females. Additionally, juveniles readily adapt to feeding on pellets. Barramundi may be raised in tanks, shallow ponds, or floating cages. Cannibalism is one of the major issues facing barramundi aquaculture, but grading, or sorting the fish by size, helps reduce mortality due to cannibalism. In regions where sustained cold temperatures occur, like southern Australia, barramundi may be grown in recirculating culture systems. These systems have the added benefit of being located close to markets.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links please go to ocean.tamu.edu and click On the Ocean.

Featured image from: https://vfa.vic.gov.au/recreational-fishing/recreational-fishing-guide/catch-limits-and-closed-seasons/types-of-fish/freshwater-scale-fish/barramundi

Script Authors: Julieta Barreiro and Samuel Marquardt

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Aquaculture: Cobia

A fish capable of growing to 6 feet, 132 pounds, and living as long as 12 years may sound like a difficult animal to grow, but aquaculture of the cobia, Rachycentron canadum, has been very successful because of this fish’s fast growth rates and excellent quality of flesh. China is the main producer of farmed cobia, but cobia aquaculture is expanding in the west with operations in the United States, Mexico, and the Caribbean.

A female cobia which will be used for broodstock, photo: Dr. Daniel Benetti, NOAA Photo Library.

Cobia are large, predatory fish that inhabit warm marine waters around the world. They are usually countershaded, with dark brown backs and white bellies. A dark band, bordered by two lighter bands, extends from the eye to the tail fin along the side of the body, which resembles a slightly flattened cylinder.

Cobia broodstock were initially captured from wild populations. Now, 1.5 -2-year-old cobia are chosen from existing stocks for spawning. Cobia broodstock are kept in recirculating or flow-through tank systems where they spawn year-round. Fertilized eggs are collected and transferred to nursery ponds to hatch, and the larvae are fed small crustaceans called copepods or microscopic animals called rotifers. As cobia grow, they are introduced to feed pellets. Weekly, the cobia are sorted by size to reduce cannibalism and ensure survival of stocks. At around 75 days old, cobia are transferred to near-shore or offshore grow out cages where they are kept until harvest. Challenges facing cobia aquaculture include overloading the surrounding environment with nutrients, disease, and escape of stocks.

The process of culturing cobia, from: http://www.fao.org/fishery/culturedspecies/Rachycentron_canadum/en

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links please go to ocean.tamu.edu and click On the Ocean.

Script Author: Danielle DeChellis

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Featured Image: https://www.fisheries.noaa.gov/species/cobia