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enough to stop the damage. And even though catches are much more sustainable now, almost all the fish are taken by bottom trawling, which is about the most destructive industrial fishing method there is.”

Pollution comes in at number three – including plastics, along with the whole gamut of toxic chemicals, heavy metals and so on that work their way into the oceans once they have served their human purpose. “We know for sure that plastics are a serious hazard, but we still don’t know how bad. We are looking at three main impacts: entanglement of animals, for example in fishing nets; ingestion, which in extreme cases can completely block cetaceans’ digestive tracts, for example; and toxicity.

“Plastics attract and concentrate persistent organic pollutants like polychlorinated biphenyls (PCBs) from seawater, and they often contain toxic additives in their own right – such as phthalates, flame retardants and polybrominated diphenyl ethers (PBDEs, which came in as replacements for PCBs) – and now they are being found in whale tissues. Lots of organisms eat microplastic particles, mistaking them for food, so the fear is that they will keep on recycling persistent organic pollutants back into the food chain long after we thought we were rid of them.”

Rogers was recently appalled to discover environmentally harmful chemicals in his supermarket shower gel – oxybenzones, best known as ultraviolet light blockers in sunscreens recently banned from commercial sale in Hawaii from 2021 because of the harm they do to coral reefs.

“At first I was really surprised to see that substance. But then I found that oxybenzones are everywhere – not just in sunscreens and shower gels, but also in shampoos, hair conditioners, makeup, mascara, and even in some foods. The concentrations may be low, but it still goes down the plughole and gets into the environment and into drinking water. And people are using multiple products. It gets into them through their skin, and the impacts of different pollutants can combine. People assume the stuff they buy is benign – if it’s on sale it must be OK. But it’s not. We all need to be aware of all these chemicals and avoid them.”

Amid this litany of oceanic gloom, there is actually some good news – at least, reason to hope that coral reefs and the marine life they support may be better than feared at surviving the warmer oceans caused by global warming. New research, some of it Rogers’, shows that coral ecosystems extend much deeper than had previously been realised, into cool waters that may serve as biodiversity refuges even as surface waters heat up. These discoveries are now causing oceanographers to rethink their division of the sea into depth zones, with a new mesophotic zone, from 40 metres deep down to 150 metres, that is far more important than previously realised.

“Most of our knowledge of coral reefs comes from scuba-diving depths down to 40 metres, which scientists call the altiphotic – shallow, sun-bathed coral depths. Then below that we have the mesophotic, where there’s still enough light for some light-harvesting corals and algae, but lower temperatures and less disturbance. What we have found is that many species inhabit both zones, but the top 40 metres is suffering the most from human activities.

“So what we need to know is this: if the altiphotic gets significantly disturbed, can it repopulate from the mesophotic? And that’s how it looks. For example, in Chagos, which has suffered intense coral bleaching, we saw only 10% coral cover in the top 10–15 metres. But out of sight at 40–60 metres, in places there was still 100% coral cover. So it’s looking like really good news. If key species can survive

Nekton Subs descend into the Abyss at these depths, that’s very encouraging. But we should still be worried – coral reefs remain highly vulnerable and threatened by climate change and ocean acidification. Another danger is that fishers are increasingly targeting this zone.”

Go down deeper still, and more surprises are lurking in the newly defined rariphotic, which extends from 150 metres down to 300 metres. Its existence as a distinct zone was first revealed in Curaçao by Carole Baldwin of the Smithsonian Institution, who realised that this zone, considered ‘deep sea’ under the old definitions, contained many species from families typically associated with shallow water. So the Nekton mission – funded by the Nekton Foundation, of which Rogers is chief scientist – decided to take a look in Bermudan waters.

“We have seen the same thing in Bermuda,” says Rogers. “For example, we found moray eels at 250 metres. The most common rariphotic fish were rough-tongued bass and saddle bass, again from families mainly found in shallow waters. But life on the rariphotic seabed is also distinctive – we have been finding entire new ecological communities at mesophotic and rariphotic depths that have remained undiscovered until now.

“Key finds include more than 40 new species of photosynthetic algae that have found a safe refuge from herbivorous fish, which range to a depth of 60 metres, and extensive coral gardens. The corals look like gigantic bedsprings in gigantic fields, along with

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Issue 310

Resurgence & Ecologist

19

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