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About Alexis Baldera
Alexis is a Conservation Biologist for the Gulf Restoration program in Baton Rouge, Louisiana, where she tracks research related to the BP Deepwater Horizon oil disaster. She loves all things ocean, wetland and oyster. When not thinking about one of these things, she is probably dreaming of her future ranch or taking names on the sand volleyball court.
Dr. Hoffmayer and a whale shark in the Gulf of Mexico. [Photo: Jim Franks]
(This blog is part of a series of interviews with scientists who are championing marine research in the Gulf of Mexico.)
A preeminent whale shark expert and ecophysiologist, Dr. Eric R. Hoffmayer is a research fishery biologist with the National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories. His interest in coastal shark species ranges from their reproduction and life history to their specific abundance, distribution and feeding ecology in nursery grounds. He has pursued a particular interest in the Gulf of Mexico’s whale sharks, the largest fish in the ocean, compiling information on their basic biology, habitat use and movement patterns.
Ocean Conservancy: How much is known generally about the whale sharks found in the Gulf of Mexico? What is the size of the population?
Dr. Hoffmayer: Ironically, even though whale sharks are the largest fish in the ocean, we still know so little about them, specifically here in the Gulf of Mexico. We know from our research efforts, as well as from research efforts of our colleagues in the southern Gulf, that whale sharks are relatively common in the Gulf. Unfortunately, due to their highly migratory nature and preference for offshore habitats, we still do not have a good population estimate for this region. However, colleagues working in the southern Gulf have estimated that between 500 and 900 individuals occur off the Yucatan Peninsula. In the northern Gulf, whale sharks occur along the continental shelf edge from Brownsville, Texas, to the Florida Keys and commonly occur off the mouth of the Mississippi River.
Nearly four years after the BP Deepwater Horizon oil disaster, we are beginning to see scientific data that points to the injury caused to important marine mammals like the bottlenose dolphin. A recent NOAA-commissioned study of 32 dolphins living in Barataria Bay, Louisiana – an area of the Gulf heavily oiled by the BP oil disaster – determined that dolphins had severely reduced health.
The animals showed multiple signs of poor health, including tooth loss, lung disease, reduced hormone levels and low body weight. These symptoms were not seen in dolphins at an unoiled comparison site or in previous dolphin health assessments unrelated to this study.
Some of the fastest growing populations in the United States are located in the Gulf Coast region. The population size in the Gulf states of Alabama, Florida, Mississippi, Louisiana and Texas is approximately 56 million, accounting for nearly 20 percent of the total U.S. population.
Growth in coastal populations is expected to put additional pressure on coastal and marine environments, including wildlife and water quality. In addition, rising sea levels, land subsidence and episodic storm events will also challenge human communities along the Gulf Coast.
Imagine if all of the animals throughout the entire state of Connecticut left or died. This is what happens every year in the Gulf of Mexico. The size of the dead zone varies—sometimes it’s as big as New Jersey or only the size of Rhode Island, but the problem always persists.
Researchers from the Louisiana Universities Marine Consortium just spent a week measuring dissolved oxygen concentrations off the coasts of Louisiana and Texas to determine how big the dead zone is this year. And they found that it is about 5,800 square miles, or roughly the size of the state of Connecticut.
This area is called “the dead zone” because dissolved oxygen levels are too low to support life. Animals that can move out of the area, like fish and shrimp, will leave, and animals that can’t, like brittle stars and mussels, will become stressed and eventually die.
Important questions about the impacts of the BP Deepwater Horizon oil disaster still linger. Some effects could go undetected for years. To fully restore the Gulf, and to make sure the Gulf and its people are recovering, we need to establish a long-term monitoring and research program. While we wait for confidential government studies to become public, little clues are emerging that give us insight into which species were injured and what this might mean for the Gulf ecosystem.
A study reported in Environmental Science and Technology tells us that one species to keep an eye on is the Gulf killifish. Through their ongoing research, the authors (Dubansky et al., 2013) determined that killifish from oil-contaminated marshes in Louisiana were impacted by the disaster. Specifically, they collected eggs from oiled and non-oiled sites before and after the disaster and raised them in a lab. The eggs from oiled sites took longer to hatch than eggs from non-oiled sites. When the late eggs did hatch, the larval fish were smaller and more likely to have heart defects than those from non-oiled sites. This indicates that the developing fish will not be able to survive and reproduce as well as eggs from non-oiled sites. Continue reading »
The tan color on this map shows the range of sperm whales in the Gulf of Mexico. The colored areas show the chance of sperm whales utilizing this habitat, with red being the highest.
Not quite a new species, but the population of sperm whales in the Gulf is distinctly different from their relatives. So different that last week, in response to a petition from WildEarth Guardians, the National Marine Fisheries Service announced that it will be taking a closer look at sperm whales in the Gulf of Mexico in order to determine if they should be protected under the Endangered Species Act. Sperm whales across the world are already listed as an endangered species, but this new designation will recognize the Gulf population as a distinct group and protect and monitor it separately from the global population.
There are characteristics of sperm whales in the Gulf that may be sufficient to classify them as a distinct group. Gulf sperm whales do not leave the Gulf and are generally smaller and use different vocalizations (probably learned culturally) than other sperm whales. Gulf sperm whales also face Gulf-specific threats such as oil and gas development, high levels of shipping traffic and noise, potential effects from the BP Deepwater Horizon oil spill, and water quality degradation near the mouth of the Mississippi River. As shown on the map above, the area southeast of the Mississippi River Delta is important for sperm whales. The outflow of nutrients from the river, upwelling along the continental slope and eddies from Gulf currents create unique ecological conditions that make this a productive area where sperm whales go to find food and potentially mates.