Barataria Bay Bottlenose Dolphins — March 2022

This month we shine a light on a very specific population of bottlenose dolphins. We can encounter them right off the coast of Louisiana, in Barataria Bay. The Barataria Bay dolphins are not much different than other populations found off the Gulf of Mexico coastline. However, they face specific stresses that threaten the survival of their population. Let’s find out about these threats!

These dolphins hang out in Barataria Bay

Barataria Bay is a sheltered inlet in between Grande Terre and Grand Isle found right on the coast of southeastern Louisiana. Historically, pirates such as Jean Lafitte would use these waters as their home base. Nowadays, humans conduct all kinds of activities in Barataria Bay like fishing and mining (sulfur, natural gas, and oil). Many ecologically important marshes and estuaries are found on the bay’s shores. They support a wide range of life stages for a plethora of species. It includes our “whale” of the month, the Barataria bottlenose dolphin.

The bay provides an incredible feeding ground for this population of dolphins. In fact, dolphins like it so much in the bay that they always come back to the same feeding grounds, even when the salinity is very low. The problem for Barataria Bay dolphins is not only the low salinity… it is also the many stressors caused by human activities.

Deep Water Horizon severly impacted the dolphins’ health

In 2010, one of the largest accidental oil spills (the largest in the US) occurred about 41 miles off the coast of Louisiana. According to the Marine Mammal Commission, over the 87 days, about 134 million gallons of oil spilled. It wasn’t just at the site affected…

The oil moved away and below the surface of the water, finding its way, via currents, to coastal Louisiana. As it reached the coast, the Barataria bottlenose dolphins suffered greatly. Initial effects came about through the aspiration and ingestion (via contaminated fish) of the oil. Later, these dolphins developed cancers and lung diseases. The long exposure to oil also caused their immune systems to decrease in efficiency, leading to more diseases. These health issues are still affecting the population today.

BP oil spill contributed to dead dolphins, scientists say, citing tissue  samples | Environment | nola.com
Pictures of dolphins swimming in oil-infested waters. Photo by NOAA – Wikimedia commons

Climat change also affects the survival of the population

All over the world, we can start to see the effects of climate change- one, in particular, is rising sea levels. In Louisiana specifically, sea levels are rising at alarming rates. As a result of human activities and the Deep Water Horizon oil spill, the natural defenses against sea-level rises, such as mangroves and marsh grasses, have been affected. It means the Louisiana coastline is more exposed to hurricanes, tropical storms, and crashing waves. The sea level keeps slowly rising, as the land progressively erodes.

There are plans to try and curb the exponential loss of the Louisiana Coast. For example, the Mississippi River Sediment Diversion Project aims to allow river water, sediment, and nutrients to flow into damaged wetlands to help sustain and rebuild land. However, scientists have warned that this increase in freshwater could kill a third of the dolphins’ population. Freshwater can cause skin diseases (lesions and ulcers) which in turn can cause lethal infections. But the heavily funded land restoration project has no plans to stop harming the dolphins because more land would bring more money to the economy. You can find more information about it in this New York Times article.

The factors that affect the survival of Barataria Bay dolphins – Credit: Whale Scientists

On top of freshwater skin diseases, the dolphins face stresses like noise, boat collisions, and chemical pollution. Finally, the loss of marshes and mangroves reduced the amount and diversity of fish in the bay, making it harder for the dolphins to find food. Life is hard for our Whale of the Month…


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Naomi Mathew is a PhD student at University of Louisiana at Lafayette. She works on bioacoustics in marine mammals from the Gulf of Mexico. She is the co-founder of Whale Scientists. You can read more about her here

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