Hypoxia

Hypoxia

Rain/Riverflow

I’m McKensie Daugherty your host for On the Ocean. Flooding in Texas is at an all-time record this year, and as a result the rivers keep swelling. This means that rivers including the Brazos, Trinity, Colorado, Sabine, and Guadalupe will be pouring the rainwater straight into the Gulf of Mexico. Because of this increase in freshwater, Texas will experience a wider and potentially longer lasting dead zone in the Gulf of Mexico. Dead zones (also known as hypoxia) are areas in the deeper ocean layers that are oxygen depleted, and because of this they can be harmful to the ocean organisms that need oxygen to survive. The freshwater contributes to the creation of a dead zone because the freshwater is lighter and will stay at the surface, while the salty ocean water is heavier and will stay below the freshwater layer. The deeper layer is cut off from the oxygen in the atmosphere and will begin to lose its dissolved oxygen in the water. But it’s not just the large amount of rain that contributes to dead zones in oceans, the timing of the flooding is also causing these dead zones to persist. For example, when there is a large amount of rain in Dallas it will take around a month for water to reach the Gulf. Since this year’s flooding has been an ongoing event, the dead zones will continue to develop and possibly expand. Dead zones can be dissipated through strong winds and waves, usually caused by storms or hurricanes. This is due to the physical force of the breaking up of layers in the ocean, the dead zone is currently predicted to span over 5,000 miles this year in the Northern Gulf of Mexico. 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.

 

More Information and Links:

Contributing Professor Dr. Steve DiMarco:

http://ocean.tamu.edu/people/faculty/dimarcosteve.html

Mechanisms Controlling Hypoxia:

http://hypoxia.tamu.edu/

Page for Gliders that gather Hypoxia data:

https://www.facebook.com/TamuGergGliders

Glider Data from Hypoxia :

Water density -Smaller means fresher and less salty. The layers of freshwater over salty water that aren’t mixing well shows areas of Hypoxia

calc_density

Dissolved Oxygen -Blue colors are low, meaning Hypoxia

sci_oxy4_oxygen

Using data like this, we can track Hypoxia over distances in the Northern Gulf of Mexico.

Week 2

Hypoxia

Stratification

I’m McKensie Daugherty your host for On the Ocean. Last week we discussed ocean Hypoxia, also known as dead zones. Ocean Hypoxia occurs in areas of the ocean where there is little to no dissolved oxygen in the water to support life. This particularly happens in the Gulf of Mexico, on the Texas coast, where rivers are dispensing huge amounts of freshwater into the ocean, causing stratification. Stratification is what happens when layers of the ocean with different densities will not mix, just like oil and water. One layer will always float above the other layer. The density of ocean water depends on two factors: the temperature of the water, and how much salt is present. Salty water is heavier than freshwater and is therefore more dense. Since the lower layers of the ocean rely on the top layers to provide oxygen from the atmosphere and photosynthesis of algae, when these layers don’t mix, it separates the supply of oxygen from the organisms living in the deeper ocean layers. As a result, these organisms can eventually run out of oxygen and die. This can destroy the local ecosystems when large amounts of fish and algae die, disrupting the food webs of the organisms in these areas. Hypoxia can also affect coastal economies, as fisherman may encounter depleted stocks and have to travel longer to find regions without dead zones to meet their quotas. It takes strong winds and waves to dissipate strong stratification, since it requires a large amount of force to make stratified layers mix. Hurricanes can be a solution in these areas, as their winds and waves are strong enough to mix the layers of the ocean sufficiently to allow the top and bottom layers to interact. Dissolved oxygen is restored to the bottom salt water, and organisms such as fish and algae can live there once again. 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.

More Information and Links:

Contributing Professor Dr. Steve DiMarco:

http://ocean.tamu.edu/people/faculty/dimarcosteve.html

Mechanisms Controlling Hypoxia:

http://hypoxia.tamu.edu/

Page for Gliders that gather Hypoxia data:

https://www.facebook.com/TamuGergGliders

Glider Data from Hypoxia :

Water density -Smaller means fresher and less salty. The layers of freshwater over salty water that aren’t mixing well shows areas of Hypoxia

calc_density

This graph shows the stratification of the layers of salty and freshwater that do not interact without the force of strong winds or waves.

 

Hypoxia -3 Nutrient Pollution

I’m McKensie Daugherty your host for On the Ocean. Last week we discussed ocean Hypoxia, also known as dead zones. Ocean Hypoxia occurs in areas of the ocean where there is little to no dissolved oxygen in the water to support life. This particularly happens in the Gulf of Mexico, on the Texas coast, where rivers are dispensing huge amounts of freshwater into the ocean, causing stratification. Stratification is what happens when layers of the ocean with different densities will not mix, just like oil and water. One layer will always float above the other layer. The density of ocean water depends on two factors: the temperature of the water, and how much salt is present. Salty water is heavier than freshwater and is therefore more dense. Since the lower layers of the ocean rely on the top layers to provide oxygen from the atmosphere and photosynthesis of algae, when these layers don’t mix, it separates the supply of oxygen from the organisms living in the deeper ocean layers. As a result, these organisms can eventually run out of oxygen and die. This can destroy the local ecosystems when large amounts of fish and algae die, disrupting the food webs of the organisms in these areas. Hypoxia can also affect coastal economies, as fisherman may encounter depleted stocks and have to travel longer to find regions without dead zones to meet their quotas. It takes strong winds and waves to dissipate strong stratification, since it requires a large amount of force to make stratified layers mix. Hurricanes can be a solution in these areas, as their winds and waves are strong enough to mix the layers of the ocean sufficiently to allow the top and bottom layers to interact. Dissolved oxygen is restored to the bottom salt water, and organisms such as fish and algae can live there once again. 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.

 

More Information and Links:

Contributing Professor Dr. Steve DiMarco:

http://ocean.tamu.edu/people/faculty/dimarcosteve.html

Mechanisms Controlling Hypoxia:

http://hypoxia.tamu.edu/

Page for Gliders that gather Hypoxia data:

https://www.facebook.com/TamuGergGliders

Hypoxia Week 4- Oxygen Isotopes

I’m McKensie Daugherty, your host for On the Ocean. The past three weeks, we’ve talked about hypoxia (or dead zones) in the ocean caused by a depletion of dissolved oxygen in the ocean water. This lack of oxygen causes die-offs in the bottom ocean layers due to stratification from flooding, as well as from algae growth and decay from nutrient excesses. Let’s address how scientists approach hypoxia, and how this data affects the public. For instance, how do we know that the runoff from certain rivers in Texas contribute to the dead zones in the Gulf of Mexico? Scientists at Texas A&M University set out to answer this question. In the past, freshwater considered to be causing dead zones in the Northern Gulf of Mexico were assumed to be from the Mississippi River. However, by using methods such as isotopic measurements, scientists were able to show that water from other river systems (in this case, the Brazos River) did in fact contribute to hypoxia in the Gulf of Mexico. Isotopes of an element have the same number of protons but a different number of neutrons, which adds extra weight to the atom. For example, there are three stable isotopes of oxygen, each having a slightly different mass. Fortunately for scientists, Mississippi River waters have a different oxygen isotopic make-up than Texas, and more specifically, the Brazos River water. By measuring waters at hypoxic zones and at rivers thought to cause hypoxia, scientists can trace the source of the freshwater contributing to dead zones using oxygen isotope analysis. By understanding which river systems contribute to hypoxia in the ocean, scientists can provide data to help better manage resources in those areas. This concludes our segments on hypoxia in the ocean, next month’s segments will address hurricanes and how they are studied. 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.

More Information and Links:

Contributing Professors

Dr. Steve DiMarco

http://ocean.tamu.edu/people/faculty/dimarcosteve.html

Dr. Ethan Grossman -Department of Geology and Geophysics

http://geoweb.tamu.edu/profile/EGrossman

 

DSC00734_O&M406_Josiah_Kai

Josiah Strauss and Kai Tao working with the isotope ratio mass spectrometer.

IMAG0537

Cavity Ringdown Spectrometer for stable oxygen and hydrogen isotope measurements of water.

Figure showing the use of oxygen isotopes to distinguish waters from the Mississippi and Brazos Rivers on the Texas continental shelf: DiMarco-2012-Fig-7

Stable Isotopes Geosciences Facility:

http://stableisotope.tamu.edu/index.php/research-education

Mechanisms Controlling Hypoxia:

http://hypoxia.tamu.edu/

Page for Gliders that gather Hypoxia data:

https://www.facebook.com/TamuGergGliders

Recent Posts

Why Mixotrophy Matters: A Competitive Edge

This is Jim Fiorendino, your host for On the Ocean.

Runners often have a big meal of pasta, or another carbohydrate-rich food before a marathon. Carbohydrates provide lots of energy when broken down, which runners need to compete. A runner who has eaten lots of carbohydrates may have a competitive advantage over a runner who has not. In the same way, mixotrophic marine phytoplankton may have a competitive advantage over strictly autotrophic phytoplankton.

Phytoplankton in the ocean were once thought to be strictly autotrophic, which means they make their own food and do not need to eat. In contrast, heterotrophs like zooplankton obtain their food by consuming other organisms. Recently, the importance of mixotrophy, or the ability to derive nutrients and food from both autotrophic and heterotrophic pathways, has become apparent within the marine microbial world.

Phytoplankton are a numerous and diverse group present in all the world’s oceans. Despite their diversity, phytoplankton compete for the same resources, specifically light, carbon, and other nutrients such as nitrogen, phosphorous, and iron. There are so many different species of phytoplankton that it seemed impossible so many could exist while competing for the same resources; surely some species would outcompete the others and drive the losers to extinction. This problem has been the subject of extensive research in the past, and has been described as the Paradox of the Plankton.

Scientists now know that, though the marine environment may seem uniform, it is quite variable. Many phytoplankton are specialized, exploiting subtle differences in their environment that other species cannot, and ensuring their survival. If a species is to succeed over some other species, it must outcompete other organisms and maintain a steady growth rate. Mixotrophy may have offered a competitive advantage to certain species of phytoplankton by supplying an additional source of food that other species did not have. This may have allowed certain species to continue to be successful when conditions were unfavorable for strict autotrophs relying solely on photosynthesis.

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.

 

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