Environmental Effects on Dolphins
Global warning: Much has been reported on how global warming is causing an increase in our oceans’ temperatures. The impact of this on dolphins is that, as their food sources seek deeper, cooler waters, dolphins must also migrate to find sufficient food. Scientists are concerned that dolphins will not be able to adapt quickly enough to these changes, and may therefore starve.
Global warming has a further impact on river dolphins. As the ice caps melt and the sea level rises, salty water is finding its way into the mouths of rivers and even moving the brackish water upstream, reducing the habitat of river dolphins.
Another disturbing impact of global warming has been that, as the sources of food for Arctic polar bears disappear, they have, in the last years, started to hunt for white-beaked dolphins. These dolphins, which normally prefer sub-arctic seas, have strayed north in search of food due to warmer sea temperatures in the Arctic and have been killed when they come up to breathe in the ice holes.
In 2015, vicious attacks on dolphins by skinny and bony aggressive polar bears were witnessed and photographed by Arctic scientists.
Toxins: Equally dangerous to dolphins is contaminated warm water, caused by the global warming effect of companies dumping chemical additives to the ocean.
It was reported in the US in March 2015 that 60% of the dolphin population on the East Coast had been killed by chemical contamination and global warming. These big companies are creating a giant, boiling cauldron of death for marine life, and the dolphins, the most fragile of marine animals, are suffering the consequences. But, sadly, the opposite can also be true.
In Mississippi and Alabama in 2011, marine scientists from Dauphin Island Sea Labs reported a correlation between large pulses of chilly water (the likely source being the melting ice caps of the Arctic ocean) entering Mobile Bay and dozens of stillborn dolphin calves washing up on the beaches.
Oil spill: Some environmentalists, however, argued that the Mississippi and Alabama issues could be yet another after effect of the Deepwater BP oil spill in 2010 – either the toxic effect of the oil itself or the toxic effect of the cleanup operation.
Dead dolphins examined by autopsy between 2010 and 2012 after the oil spill in the Gulf of Mexico showed levels of bacterial pneumonia, adrenal disorders and severe lung lesions that were far more serious than a control group of bottlenosed dolphins not in the oil spill area. “These dolphins had some of the most severe lung lesions I have seen in the over 13 years that I have been examining dead dolphin tissues from throughout the United States,” said Kathleen Colegrove, the study’s lead veterinary pathologist, based at the University of Illinois, in a statement reported by Newsweek magazine on 20 May 2015.
Dolphins take deep breaths of air right at the water’s surface, where oil fumes would be most concentrated, and hold that air in their lungs for long periods while they dive
The rate of dolphin deaths in this area from 2010 to 2015 was four to five times higher than normal levels. These oil spill impacts are not uncommon. May 19th 2015, Refugio oil spill near Santa Barbara prompted media reports of dead dolphins and other marine wildlife being washed up on the shores with mouths full of tar. And be aware that the statistics only show the surface of the problem – marine scientists believe that the bodies of most marine wildlife killed in this way sink to the bottom of the ocean, never to be found or counted.
Dolphins swim through oil during the Deepwater Horizon oil spill in April 2010. Source: NOAA