The Hidden Ocean Pollution Killing Marine Mammals
Noise and chemical pollution in our oceans are affecting marine mammals' ability to navigate, communicate and detect danger.
I've worn glasses since the age of five, my hearing isn't brilliant in busy environments and, like many others, I lost my sense of taste during Covid-19, which was incredibly disorientating. Perhaps once our senses are pushed to their limits, we begin appreciating them all the more. But we're certainly not the only ones relying on multiple senses: marine mammals depend on them to communicate, navigate, feed, hear and detect danger.
It's hard for us to imagine how marine creatures sense within their world. What's clear is that the picture is complex, and that human-induced impacts make that even more challenging.
Pollution is ubiquitous but not homogenous. There is oil and gas exploration on the seabed, military exercises, increasing shipping traffic and the relatively new threat of deep sea mining. Add to that sewage outflows, industrial discharge and agricultural run-off, the marine environment is getting busier, noisier and more polluted. So what are the hidden dangers to marine life?
As a marine strandings volunteer for the Devon Wildlife Trust in south-west England, I'm regularly asked to take photos and measurements of marine mammals stranded along my local coastline. Sometimes, there'll be noticeable injuries, rake marks from the teeth of bottlenose dolphin attacks perhaps, long straight cuts in the skin from a fishing line or occasionally a tail clean cut off as a result of bycatch. Usually though, the actual cause of death isn't simple to identify. A crack team of scientists are on a mission to discover more about how human-induced impacts affect UK populations of whales, dolphins and porpoises.
To find out more about their research, I visited Rob Deaville, a strandings scientist at the
UK Cetacean Strandings Investigation Programme, this summer. Every year, he dissects about 150 stranded porpoises, dolphins and whales to find out what might have killed them. "In some cases, it can be very evident, for example bycatch, ship strike, grey seal predation, bottlenose dolphin attack, those causes of death are really obvious. But even a high level of pollution is not necessarily causal in an animal's death, it's more associated," says Deaville. "You're looking through a keyhole at one aspect, at what I call the terminal end, and then trying to look backwards at what that animal has experienced throughout their lifetime.
The hidden ocean pollution killing marine mammals