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Forests have long yielded lifesaving medicines. From cancer drugs like vincristine to quinine for malaria, about a quarter of the medications used in developed countries are derived from plants — in developing countries, it can be as much as 80 percent.

Increasingly, scientists are unlocking a new, natural medicine chest: the sea. Worldwide, 21 marine-derived medications have been approved for use — and a potent new antiviral sourced from a Mediterranean sea squirt is in clinical trials for treating COVID-19, Stephanie Stone reported for Scientific American.

Sea squirts are members of a group of invertebrates known as tunicates, which are the source of many pharmaceuticals derived from the sea — including the new antiviral, plitidepsin.

These unassuming creatures feed on plankton, which they siphon through sieve-like structures. “Along with their food, they pull in viruses and other pathogens, so they need strong chemical defenses to fight off infectious organisms — and that makes them promising sources for medicines,” Stone wrote.

There’s a twist, though. Over the past few decades, scientists have found that most of these defensive substances are produced by microbes that live symbiotically within the creatures' tissues, rather than by the invertebrates themselves.

Though vastly understudied, marine microbes could hold the key to new medicines. Stone writes that the pandemic has highlighted the need for “a deeper pool of drugs to treat emerging infectious diseases,” as well as a new drugs to counter growing microbial resistance to established antibiotics.

But as scientists explore the potential of marine-derived medicines, the clock is ticking on regulations that would allow the world’s first deep-sea mining to begin — a process that would essentially scrape the seafloor for precious metals, killing fish, coral and other sea creatures in the process.

The International Seabed Authority, a United Nations agency tasked with overseeing mining in international waters, last month ended negotiations in a stalemate. That means plans to open parts of the ocean to mining for manganese, nickel, cobalt and other metals could move forward next year without environmental regulations.

Global oceans already face a myriad of threats. Scientists argue that deep-sea mining could be devastating to marine biodiversity — and, given that more than 80 percent of the ocean remains unexplored, the consequences of industrial mining operations are not yet fully understood.

• FURTHER READING: Newly discovered coral species face uncertainty in Pacific’s depths

In addition to the immediate impacts on the seabed, deep-sea mining could affect interconnected ecosystems by generating large sediment plumes, toxins and noise that would negatively affect marine life far beyond specific mining sites. These conditions are bad in any ocean ecosystem, but particularly dire in the deep sea, where some corals and sea sponges live over hundreds or even thousands of years — and are accustomed to stable conditions, akin to the ancient redwoods of California. If destroyed, it could take thousands to millions of years for these ecosystems to recover, if at all.

“Currently, we cannot predict what the impacts of mining will be on the vast and diverse ecosystems of the deep sea and other parts of the oceans,” said Emily Pidgeon, Conservation International’s vice president for ocean science. “We are only just beginning to understand the potential risks to the biodiversity of the oceans. Before any mining can begin, science must first clarify if and how deep-sea mining might be possible without endangering ecosystems that are still largely unknown.”

Read the full article here.

FURTHER READING:

• In high seas, scientists see a lifeline for coral reefs
• 5 ways you can help protect the ocean — in and out of the water

Vanessa Bauza is the editorial director at Conservation International. Want to read more stories like this? Sign up for email updates here. Donate to Conservation International here.

Cover image: A diverse coral community in the North Atlantic (© NOAA Office of Ocean Exploration and Research)