Can Ukraine’s Seaweed Forests Survive Russian Occupation?

When scientists study the Black Sea’s coastal seaweed forests, they often dive beneath the surface to see them in person. Formed by two species of brown algae in the genus Cystoseira, these ecosystems can look dull from a distance. “But when you actually dive deeper, you can see the biodiversity, and these various interesting invertebrates and fish species which are moving there,” says marine biologist Sofia Sadogurska.

^{Text: Elyse Hauser}

The brown algae species are ecosystem engineers, forming the foundation of a forest-like environment. They provide a refuge where many other species eat, reproduce, and rest.

“These ecosystems are called forests not because of their size, but because of their structure and their importance for the marine and coastal areas,” says Sadogurska, who specializes in studying the forest-forming seaweeds at Ukraine’s National Academy of Sciences.

Now, though, nearly all of Ukraine’s seaweed forests are under Russian occupation. As the full-scale war stretches toward its fourth year, scientists worry about the status of these crucial ecosystems.

The keystone seaweeds

In the underwater forests, red and green seaweeds grow on the brown seaweed species, just as ferns sometimes grow on trees. Invertebrate animals, like sponges and shrimp, live among the lush thickets. Many types of fish, including some frequently fished by humans, use these places as nurseries. “It’s one of the most biodiverse ecosystems in the coastal areas of the Black Sea,” says Dimitar Berov, a marine biologist at the Bulgarian Academy of Sciences.

The forest-forming seaweeds originally migrated from the Mediterranean but are now highly adapted to the Black Sea environment, which is far from the open ocean and only half as salty as the Mediterranean. “From the conservation point of view, it’s absolutely essential to have these ecosystems because they sustain the whole biodiversity of the coastal areas in the Mediterranean-Black Sea connected basins,” says Sadogurska.

The underwater forests grow well in clean water where there are hard, rocky surfaces to attach to. Because of this need for cleanliness, they’ve long been threatened by pollution from human activities. Many of these ecosystems in the Black Sea are in decline today. “Ecologically speaking, they’re very sensitive to pollution of various sorts,” says Berov. He explains that the slow-growing, biodiverse forests can be overtaken by fast-growing algae that’s better adapted to polluted waters.

In the 20^th century, due to these impacts, “these underwater forests disappeared entirely in the northern part of the Black Sea,” says Sadogurska. Some have recovered, but many still haven’t.

This makes the few remaining seaweed forests of Ukraine—located mostly on the rocky coastline around Crimea—all the more precious. Each of these forests forms the basis of an entire ecosystem. “If they disappear, tens of species disappear with them,” says Sadogurska.

But in 2014, Russia occupied Crimea. Ukrainian scientists lost the ability to manage and monitor key seaweed forests. Still, they continued working in nearby areas like Dzharylhach Island, which is the biggest island of Ukraine and an important location for these ecosystems. “It was a kind of refugium for my research, after the occupation of Crimea,” Sadogurska recalls.

Then, Russia’s full-scale war on Ukraine began in 2022, and access to the seaweed forests of the northern Black Sea was almost entirely lost.

Conflict brings new risks

Now, scientists aren’t sure how the region’s algae forests are faring. “We don’t really know what’s happening along the coast of the Crimean Peninsula and in the Azov Sea, and the Russian side of the Black Sea,” says Berov.

Still, the war brings clear ecological risks to the region. Pollution enters the sea when fuel spills from sunken military equipment like ships, planes, and rockets. More pollution has come from coastal infrastructure destroyed during the hostilities. And, in late 2024, a massive oil spill from two Russian tankers spread across the northern Black Sea, large enough to be seen from space.

On a smaller scale, explosions from underwater mines harm nearby ecosystems. Anchors from warships, grinding along the seafloor, can also physically damage the underwater forests.

Scientists are aware of the possible damage, but there’s little action they can take while the occupation and hostilities drag on. “So, for the last 11 years, the majority of these ecosystems are under occupation,” says Sadogurska. She adds that this doesn’t necessarily mean the seaweed forests are disappearing or destroyed completely. “But for us [scientists], it means we do not have the possibility to monitor all the areas. We do not have the possibility to make conservation measures.”

A resilient ecosystem

In spite of the risks, there are reasons for hope. One seaweed forest of Ukraine remains unoccupied, in the estuary where the Tylihul River meets the Black Sea. There, the ecosystem is faring well, offering Ukrainian scientists a place to continue their research. Even when the 2023 destruction of the Kakhovka Dam sent polluted freshwater flooding into the Black Sea, those waters didn’t reach the estuary, and the seaweed forest stayed protected. “The communities are still thriving there, and we had some expeditions last year,” says Sadogurska.

In other Black Sea countries, like Bulgaria, experts are also working to preserve the forests in their waters. This helps support the entire Black Sea environment. “We’re designating measures to keep them in good condition,” says Berov, a process that involves mapping the ecosystems and setting conservation guidelines.

Ukraine also has plans to expand its marine protected areas and add new ones—though for now, those plans have been halted by the war.

When placed under protection, the underwater forests can show a healthy ability to bounce back from harm. In Bulgaria, “the ecosystem is resilient enough that it’s actually restoring itself, provided we don’t really stress the environment, and decrease the nutrient pollution,” says Berov. 

This resilience offers hope for the occupied seaweed forests of Ukraine. Even after the war’s eventual end, lingering dangers from mines will make these coastal areas hard to study. Still, Ukrainian researchers are eager to restart the critical work of research and conservation. “We as scientists are ready to work there, because we have some data from before the war, and it will be really important to understand what was going on there, what is the impact, and what we can do in the future,” says Sadogurska.  

^{About Deep Sea Reporter: Our ambition is to examine and report on issues related to the sea and the life that exists beneath its surface. We operate in the public interest and are independent of political, commercial, and other interests in society.}