Scientists Ponder Human Role in Mid-Atlantic Dolphin Die-Off

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healthy bottlenose dolphins

As our human footprint on the planet grows heavier, our activities may have complex and unforeseen effects in far reaching places like the oceans.

In one ongoing instance, the number of bottlenose dolphins beaching themselves along the Mid-Atlantic coast has skyrocketed this summer. The National Oceanic and Atmospheric Administration has declared an “unusual mortality event,” launching an investigation into what might be causing the deaths.

Since July roughly 70 dolphins stranded themselves on Virginia beaches. In previous years, the state has seen less than a dozen dolphin strandings during the summer months. New Jersey, which sees even fewer strandings in a typical July, was the site of 20 dolphin deaths last month. More than the usual number of dolphins have also beached this summer in New York, Delaware and Maryland, according to the NOAA. All told, nearly 150 dolphins have died.

stranded dolphinThe stakes of the episode are high because the deaths are reminiscent of a 1987-88 die-off that claimed nearly 800 bottlenose dolphins from the same Mid-Atlantic population. That episode, which caused the same mid-Atlantic dolphin population currently affected to be labeled “depleted,” ultimately prompted Congress to create the unusual mortality event protocol that was invoked on August 8.

“The timing of it all on the 25th anniversary, with the same species at the same time of year in the same geographical area has people really alarmed,” Trevor Spradlin, a marine mammal biologist with the NOAA’s Marine Mammal Health and Stranding Response Program, told Singularity Hub.

Marine mammals, and bottlenose dolphins in particular, have paid a high price for human industrialization. The dolphins — Flipper’s species — are among the most frequent victims of unusual mortality events. Die-off events appear to have increased globally since the late 1980s, in some cases spurred by disease or by toxins produced by algae that flourish in polluted waters.

On the west coast, bottlenose dolphins have been among the marine mammal species likely impacted by the Navy’s use of sonar. In the Gulf of Mexico, the animals were seriously affected by the Deepwater Horizon oil spill of 2010. (According to an NOAA report, “Coastal dolphins have been observed with tar balls attached to them and seen swimming through oil slicks close to shore and inland bays.”) On the east coast, the dolphins frequently get snagged in fishing nets, according to the NOAA.

midatlantic_strandings_graph-edThe bottlenose dolphin die-off in the late 1980s was eventually attributed to morbillivirus, a virus related to the one that causes the measles in humans. A virus may be behind the current die-off, as well.

“Based on the rapid increase in strandings over the last two weeks and the geographic extent of these mortalities, an infectious pathogen is at the top of the list of potential causes for this unusual mortality event, but all potential causes of these mortalities will be evaluated,” an NOAA statement said.

Preliminary testing suggests that one of the beached dolphins was infected with the morbillivirus, which can cause skin lesions and pneumonia. Several animals also presented with evidence of pneumonia.

“Anything like that is going to be a red flag,” said Spradlin. “We want people to be aware that if this is going to be a repeat of 25 years ago, it could have very serious implications for that stock of dolphins.”

The morbillivirus was only identified in dolphins and other cetaceans in the late 1980s. Researchers don’t know if it is spread or exacerbated by human activity — for instance, if certain types of pollution might lower the dolphins’ immune response, leaving them more susceptible to the virus. Morbillivirus could also simply hit upon particularly lethal variants from time to time, like the flu.

Tissue samples collected from the dead animals must be analyzed before researchers can say with any certainty that the deaths are attributable to a virus, or whether bacteria or chemical pollutants or even acoustic trauma may be to blame, Spradlin said.

“As we find out more information about the cause or causes, we can try to implement particular measures to quiet it down, hopefully. But if it’s Mother Nature there may be little we can do,” said Spradlin.

The NOAA will post any updates on its investigation into the bottlenose dolphin deaths on its website.

Photos: Dominic Sherony via Wikimedia Commons, NOAA

Discussion — 4 Responses

  • David Bartle August 15, 2013 on 1:25 pm

    Is it possible that these beachings correlate to the solar cycle? I am not an expert on dolphins or the cosmos but that would be my (more than likely wrong) guess if I were in 7th grade.

    • David Bartle David Bartle August 15, 2013 on 1:34 pm

      I probably should have suggested UFOs as that would probably be more likely than the sun .

      An unbelievable number of dolphins died last year in Peru. The cause of death seems to be argued between natural causes (virus, other natural cause); and manmade cause (sound waves from oil exploration explosions). http://www.bbc.co.uk/news/world-latin-america-18169586

      I hope the investigation this time around is more conclusive.

  • dabraat August 18, 2013 on 6:08 am

    Was swimming in early July at Robert Moses in Long Island, and this weekend at Fenwick Island in Delaware. My son and I both immediately noticed that the water seemed much saltier at Fenwick, very irritatingly so. There was also a dredge working on sand replenishment a few hundred yards off the beach. We always see dolphins when we’ve been at the beach around the DelMarVa peninsula, but did not see one dolphin the entire two days we were there.

  • FacebookUser10 November 12, 2013 on 11:30 am

    Guys,

    I am a chemical engineer. After 10 months of data collection and plotting algae blooms, fish and mammal kills, sinkholes and waterspouts in Google Earth my data is showing me it is our Doppler radar weather towers (which were recently upgraded to Dual Pol making them even more deadly) energizing the atmosphere causing the deaths of dolphins, whales, starfish, algae blooms, bee kills, bats dying, increased autism, increase in arge sinkholes. The high powered, low frequency Doppler waves are getting attenuated by the atmosphere and reflected back to Earth and the waterways, weakly ionizing all of us in the process. They are designed to penetrate THROUGH water. Each NEXRAD/TDWR tower is transmitting 0.25-1.25 megawatts of energy(enough to power up to ~ 500 homes) above our heads 24/7 and they have never done any biological studies on the effects. I am being very sincere.