Examining impact on the deep

Andrew Sweetman

Deep sea functions are critical to a host of human interests, from augmenting fisheries’ numbers to buffering the ocean against pH changes and the effects of ocean acidification.

Professor Andrew Sweetman

The deep sea and the functions it carries out underlie the healthy functioning of ocean ecosystems. It also provides valuable ecosystem services that humans and the rest of the biosphere have relied on since the beginning of time. 

The health and sustainable functioning of the planet are therefore highly dependent on the deep sea, 200m below sea level. Professor Andrew Sweetman is exploring the impacts of human activity on the deep sea to determine better management principles.

“Presently, my research team is exploring the impacts of deep-sea mining and climate change on the deep sea through in-situ experiments and computer modelling,” he explains.

“We’re also involved in environmental baseline surveys for deep-sea mining contractors to help them gather environmental information that will assist them in deciding where to mine in order to reduce harmful effects on the environment.”

His team has recently shown that the deep sea and the creatures that reside there are facing a bleak future due to food shortages and changing temperatures. A recent study showed that food supplies at the seafloor in the deepest regions of the ocean could fall as much as 55 per cent by 2100. This would result in widespread starvation of the animals and microbes that exist there.

Moreover, the team has predicted that future changes in temperature, pH and oxygen levels are also likely to take a toll on these sensitive ecosystems. “This situation will be exacerbated by drilling for oil and gas, dumping of pollutants, fishing and other anthropogenic impacts,” he states.

Real-world impact

One strand of Professor Sweetman’s work focuses on the role of jellyfish in deep-sea ecosystems. For centuries, jellyfish have had a bad reputation in the marine community. Either thought of as dangerous or superfluous, scientists long denigrated these creatures.

As the climate has changed, however, scientists have re-evaluated this assumption, especially since their population has ballooned in recent decades. After performing dozens of experiments in which the team offered dead mackerel and jellyfish to scavengers at the bottom of the ocean floor, he discovered startling results.

“We knew the scavengers were going to devour the mackerel. However, we were surprised to find that they also devoured the jellyfish in the same amount of time,

“We now have evidence that jellyfish can significantly alter the way seafloor ecosystems function and our latest research suggests jellyfish may be able to support commercial fisheries also. Not bad for an animal with no brain.”

Moving forward, Professor Sweetman and his team will continue to explore how human activity is impacting the world’s deep-ocean ecosystems. “To come up with solutions to real world problems, we first need to identify what issues arise from specific practices. My group’s research is first identifying these problems so we can then focus on the solutions,” he concludes.

Read the latest news about Professor Sweetman's research:

Mining waste too sharp for fjord
Deep sea lifting of polymetallic nodules
2500m beneath the sea

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