As the 21st century began, pressures from human industrial activities on the marine environment accelerated rapidly. Back to Blue interviews Jesse Ausubel, director of the programme for the human environment and senior research associate at Rockefeller University, about this industrial revolution at sea, which has largely been obscured from public view, and how to bring it to the surface.

“If you look closely, massive industrialisation of the oceans is happening, and it will be very hard to reverse,” says Mr Ausubel. Visibly water-based industries like shipping, aquaculture and offshore wind farms are contributing factors, but so too are less visible ones. Seafloor telecommunications cables, undersea oil and gas operations, and desalination outflows number among this other category. The cumulative impact of all these activities is compounding the contamination of our oceans.

Ms Ausubel distinguishes between acute and chronic forms of ocean pollution. Acute incidents, like oil spills or the bizarre case of 28,800 bath toys spilling into the North Atlantic in 1992 after a cargo container went overboard, create an immediately noticeable impact. They attract public attention and are more likely to elicit responses. Another example was the BP-chartered Deepwater Horizon oil rig exploded in 2010, killing 11 workers and spilling millions of barrels of oil into the Gulf of Mexico, BP and partners were compelled to remove most of the oil from beaches and pay over US$60bn in criminal penalties, civil fines, natural resource damages, economic claims and clean-up costs. Such acute disasters spur resource mobilisation and calls for accountability.

By contrast, chronic pollution accumulates more insidiously from numerous persistent but diffuse sources. This may prove even more environmentally devastating. Yet its sources are more easily swept under the rug. “When it comes to issues like lubricants leaking from wind farms, or paint washing off the hull of ships, it’s harder to get people to focus, even though these chronic problems accumulate into serious problems,” says Mr Ausubel.

Paint washing off ship hulls, for instance, releases at least 60,000 tonnes of microplastics, the equivalent of 6 billion plastic bottles, into the sea yearly—paint from road run-off, construction waste, and industrial sites contributes even further. Textile fibres, laundry detergent chemicals and dyes are regularly washed into rivers and oceans via our laundry machines. While more conscious consumption habits can help, says Mr Ausubel, the industry will ultimately need to take charge of the problem by rethinking these processes entirely.

This responsibility exists in every industry that interacts with the ocean. “How much offshore aquaculture, shipping, fishing, seabed mining, are we going to allow?” asks Mr Ausubel. “The industrialisation of the oceans is relentless and global, and all of these industries are growing. It requires careful attention across the entire life cycle. You have to think about upstream factors, operations, and end of life.”

The oil and gas sector has long been the largest industry in the ocean economy, accounting for a third of its value. Many countries continue to expand undersea oil and gas exploration, sometimes in sites earmarked for offshore wind, as the UK did this year. The impact of oil and gas on the ocean will matter throughout the 21st century.

But the growing renewable energy industry has its own problems for the ocean. “Energy can be renewable, but there’s no such thing as green energy or clean energy,” says Mr Ausubel. “All forms of energy generation have very significant environmental fallout, despite how they have been marketed. You pick your poison—whether it’s chemical, acoustic, radiation, disturbing ocean currents, there is inevitable fallout that will need to be managed.”

Offshore wind farms and tidal energy farms, while offering low-carbon energy, emit noise pollution and obstruct marine space, impacting various species’ behaviour and ecosystem functioning. Their construction can also churn up sediments and influence water temperature. Meanwhile, corrosion protection for wind turbines results in chemical pollution and releases metals into the ocean. There are further knock-on effects, as Mr Ausubel explains. “If you’re going to have wind energy, you have to collect electricity, which requires laying seafloor cables. And then there are end-of-life cycle problems: what do we do with 50,000 towers 800 feet high when wind farms don’t work anymore?”

Mr Ausubel studies the impact of some lesser-known disruptions in the ocean, particularly the acoustic environment. “All marine industries have an acoustic footprint,” he says. “Any underwater structures that reflect, deflect or absorb sounds, including wind turbines and aquaculture structures, will affect the ocean soundscape. Changing the topography of the sea floor by trenching or laying cables is also going to make noise and change sound propagation.” Animals use sound for mating, hunting or communicating with one another, so acoustic disturbances can have significant impacts on animal behaviour and, consequently, biodiversity. Scientific initiatives such as the International Quiet Ocean Experiment, under way since 2015, aim to get a better sense of the baseline of the acoustic environment of the ocean.

Other mechanisms include monitoring environmental DNA, or eDNA. “This is a blessing because it allows affordable, non-invasive, frequent and flexible monitoring,” says Mr Ausubel. “We collect a litre of water from the ocean, extract fish DNA from the sediments, sequence it and match it against a database in order to have a survey of what species are living there, their abundance, distribution and diversity. This is how we can see how ocean industries and clean-up techniques are changing fish biology.”

The transition towards sustainable ocean industries is an inevitable and essential path, but it is crucial to consider the new and unique challenges these emerging industries may pose for the marine environment. “Most maritime industries have low margins and strange profit structures because they rely heavily on subsidies. As executives are afraid that these subsidies will go away, they will often expedite the environmental review process so that it’s done in a hurry, and may not take into account all the potential impacts,” explains Mr Ausubel. Comprehensive environmental review processes are indispensable and must encompass not only the visible impacts but also the less evident cases of chronic harm inflicted on oceans by industrial activities, such as paint flakes, noise pollution and other cumulative stressors. Failing to identify these seemingly minor but persistent threats could lead to massive ecosystem disruptions over time.