Texas A&M Graduate Student Spotlight: Modeling Hypoxia

Imagine if all the oxygen were sucked out of the air where you lived. Pretty terrifying, right? This is a major problem for marine life in areas of the ocean where dead zones form. Dead zones develop when dissolved oxygen at the bottom of the coastal shelf reaches critically low concentrations that are harmful to the organisms living there. A “dead zone” develops every summer in coastal waters off the Texas and Louisiana coast, and has been a major concern of scientists for decades.

Map of hypoxia in the Gulf of Mexico, from: https://gulfhypoxia.net/wp-content/uploads/2018/07/2018_SW_BDO_2018-07-27_ALL_web.jpg

Mapping the region affected by low-oxygen bottom water is essential to understanding the dynamics of dead zones. This is not an easy task. Each year a research vessel maps the hypoxic region of the Texas-Louisiana shelf (hypoxia refers to low-oxygen conditions), but the marine environment is constantly changing, and during the week it takes for a ship to traverse the region experiencing hypoxia, the shape of the dead zone has changed.

Below: Bottom oxygen simulations for August – September 2010 on the Texas/Louisiana Shelf. Harmful low -oxygen concentrations form mobile patches. Simulation made by the Physical oceanography Numerical Group (PONG) at Texas A&M University using the Regional Ocean Modeling System for the Texas-Louisian shelf.

To better inform direct sampling in the field from a research vessel, scientists use mathematical models that simulate ocean currents and conditions to approximate the formation and changes within dead zones. These ocean models resemble the atmospheric models used to predict weather and are based on equations that describe physical processes, all interpreted by powerful computers. One advantage of using models is the ease with which scientists can run experiments where some mechanisms or environmental conditions within the model are altered. The model responds to these changes, giving scientists important insight to the processes at work within marine environments. For example, scientists can explore how the area of the hypoxic region will change if the freshwater input from the Mississippi river increases or decreases, or how storms of different strengths can disturb the hypoxic region by mixing the water on the Texas-Louisiana shelf. Models are not perfect; they are often limited by data or do not capture all the dynamics of marine ecosystems, but models and field observations, when used to complement one another, greatly improve scientists’ understanding of marine systems.

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: Veronica Ruiz Xomchuk

Editor: James M. Fiorendino

Contributing Professor: Dr. Kathryn Shamberger

Texas A&M University Graduate Student Spotlight: Deep Sea Corals

Coral reefs, like the Great Barrier Reef in Australia, are some of the most brilliant and biologically diverse ecosystems in the oceans, but did you know there are corals in the deep ocean, too? In fact, most species of coral are found at depths below 1600 feet, where they grow to be thousands of years old. These deep-sea corals are a very important habitat for deep-water fish, and they are of interest to scientists because, like shallow water corals, a record of past ocean climate conditions is stored within their skeleton. These coral archives can fill in gaps in our understanding of the deep ocean that help scientists piece together the history of Earth’s oceans and climate. Of course, living at such great depths makes these corals difficult to study. Using advanced technology like Remotely Operated Vehicles and deep-diving submersibles allow scientists to study the environment of deep-sea corals.

Locations of deep-sea coral communities along the Hawaiian-Emperor seamount chain. Photo provided by Sarah Hall
Locations of deep-sea coral communities along the Hawaiian-Emperor seamount chain. Photo provided by Sarah Hall

Researchers in the department of Oceanography at Texas A&M are currently engaged in research regarding deep-sea corals, specifically the effects of humans on deep-sea coral ecosystems. Current areas of interest include the Northwestern Hawaiian Seamounts, with a focus on Corallium, a precious coral sometimes known as red or pink coral. Precious corals are used for jewelry, but are also accidentally damaged or destroyed when deep-sea commercial fishers use nets that drag along the sea floor. Scientists study different areas of the Hawaiian seamounts, comparing non-fished areas with regularly-fished areas, and areas that have been recovering for the past 40 years following the expansion of the US Exclusive Economic Zone, or EEZ, which limited fishing activities that fall within the EEZ. Studying deep-sea coral recovery after damage by fishing activities will help determine the sustainability of fishing practices, and help develop effective management and conservation strategies.

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: Sarah Hall

Editor: James M. Fiorendino

Contributing Professor: Dr. Kathryn Shamberger

Texas A&M University Student Spotlight: Tracking Monsoons with Thorium

Understanding ocean processes often requires a little detective work, identifying clues left in the marine environment for scientists to find. The Niger River’s flow and discharge are controlled by the amount of regional precipitation in West Africa. West Africa’s regional precipitation is controlled by the west African monsoon, when winds shift seasonally causing both a wet and dry season. Changes in monsoon intensity can affect the stability of regional infrastructure, as well as financial and food security.

Changes in west African monsoon intensity as a response to climate events can be studied by looking at the sediments deposited in the Niger River Delta. An isotope is an element with a specific number of neutrons in its nucleus; some isotopes in marine environments can be used as tracers, informing scientists about chemical or physical processes. Uranium and thorium-230 isotope ratios in sediment can be used to estimate rates of sediment accumulation, and if the sediment has been transported to or from the surrounding area.  If the amount of thorium-230 found in the sediment is higher than the theoretically-estimated amount, new sediment has been transported to the area and if it is lower, sediment has been removed.

Shifting of the Intertropical Convergence Zone is responsible for monsoons.
Shifting of the Intertropical Convergence Zone is responsible for monsoons.

 

Another form of thorium, thorium-232, can be used to study sediment sources. Thorium 232 is virtually entirely derived from continents.  Previously, thorium-232 was only used to study the amount of windblown sediment to the open ocean.  However, current research in the department of oceanography at Texas A&M is hoping to expand the use of both thorium 230 and 232 to study changes in the delivery of sediment and other material to the ocean by rivers. Since the Niger River’s flow and discharge is controlled by the amount of regional precipitation, and West Africa’s regional precipitation is controlled by the west African monsoon, the amount of sediment delivered by the Niger river should reflect the intensity of the monsoon.

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: Ruby Schaufler

Editor: James M. Fiorendino

Contributing Professor: Dr. Kathryn Shamberger

Texas A&M University Graduate Student Spotlight: Iron Colloids

Iron Colloids

How long can you hold your breath? 30 seconds? A full minute, maybe longer? Oxygen in the air we breathe is an essential component of chemical reactions in our bodies that keep us alive. Oxygen is produced as a byproduct of photosynthesis, the chemical pathway by which plants make food for themselves using energy from the sun. Only about half of the oxygen in the air comes from land plants, however; you can thank microscopic marine plants, called phytoplankton for the other half.

To photosynthesize, phytoplankton need iron. Just like humans need vitamins and minerals to be strong, phytoplankton need iron to perform basic metabolic functions. Dissolved iron is considered bioavailable for phytoplankton to use for photosynthesis, and a significant portion of this dissolved iron is considered to be colloidal, which means that instead of being truly dissolved, the iron is actually present as tiny particles that are so small that they do not sink.  Using a new method that separates colloids in to a spectrum of sizes, scientists at Texas A&M can learn a lot about the composition of these colloids and structure of colloids, including their origin and chemical processes that affect them. Answering these questions about colloids along with learning about coastal processes such as plankton blooms, ocean currents, and river runoff, can give insight into the role that iron colloids play in the marine environment and just how important they may be for phytoplankton growth.  Understanding how iron colloids impact phytoplankton can provide important insights regarding marine ecosystems such as the dynamics of fish populations and climate change, which are linked to the marine phytoplankton.

kimber_desalvo_fig1
The above figure shows the size separation of different iron pools in the oceans; soluble (dissolved), colloidal, or particulate. Image provided by Kimber De Salvo

 

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: Kimber De Salvo

Editor: James M. Fiorendino

Contributing Professor: Dr. Kathryn Shamberger