Marine Animals in the Strait of Hormuz Don’t Get a Ceasefire

Beneath the surface of the Strait of Hormuz and the surrounding Gulf lies a biological sanctuary. The region is home to around 7,000 dugongs and fewer than 100 Arabian humpback whales—a nonmigratory population that cannot leave these waters.

The United States and Iran last week agreed to a two-week ceasefire, following weeks of escalating tensions that disrupted shipping through the Strait of Hormuz.

But the ceasefire has not cleared the water. Naval mines, residual military activity, and congested shipping lanes mean the strait remains a high-risk environment—not just for vessels but also for the ecosystems beneath them.

With 800 vessels currently trapped behind a monthlong maritime blockade, shipowners are preparing to move. But while headlines focus on oil and trade, a different kind of resident is struggling to navigate the Arabian Gulf.

These species are extremophiles, adapted to heat and salinity levels that mirror what much of the world’s oceans may face by 2050. Scientists see them as a living blueprint for how marine ecosystems might survive climate change—if they survive this moment.

Sound Is Survival

Underwater explosions and military sonar don’t just scare whales, they can physically blind them, leading to stranding and death. The Arabian humpback whale, unlike its cousins in the Atlantic, does not migrate. For them, the Gulf is not a corridor but home, a permanent habitat.

Olivier Adam, a researcher at Sorbonne University Abu Dhabi, says that the Gulf’s resident cetaceans—better known as marine mammals—have limited options: Either abandon their habitat or remain and endure prolonged exposure to noise.

In the case of Arabian humpback whales, relocation is not realistic, as they are one of the only populations that do not migrate between feeding and breeding areas. “These baleen whales have no way to escape,” he says.

The sounds they endure are more than just a nuisance. They are a physical and social barrier. Whales rely on sound for nearly every essential function: feeding, navigation, reproduction, and social interaction. When that acoustic environment is disrupted, the effects are immediate. “Their emitted sounds, which are therefore important for structuring their social groups, can be masked by underwater noise pollution from human activities at sea,” Adam says.

Humpback whales communicate in low-frequency sound—meaning the same range filled by ship engines and sonar—making them especially vulnerable to disruption.

Adam explains that underwater noise from maritime traffic interferes with feeding behavior and can have physiological effects on the auditory system. “The radiated underwater noise generated by maritime traffic disrupts the feeding of humpback whales.”

As noise levels rise, whales reduce their diving activity—effectively entering a forced fasting period that weakens them over time.

From Disruption to Damage

In the narrow, 21-mile-wide funnel of the strait, military activity introduces shock waves and pressure changes that marine species are not built to withstand. Underwater explosions can be strong enough to kill fish outright and damage the auditory systems of larger marine mammals.

Aaron Bartholomew, professor of biology, chemistry, and environmental sciences at the American University of Sharjah, suggests that “while whales and dolphins may temporarily move out of areas where there is significant naval sonar activity,” the intensity of modern maritime conflict poses lethal risks.

Adam warns that the impact can be lasting: “These explosions can also damage the auditory system of cetaceans, which may temporarily or permanently lose their hearing.” Even when not immediately fatal, the effects can weaken animals over time and disrupt their ability to survive in already stressed conditions.

Naval mines introduce similar risks even before detonation. When triggered, they generate high-pressure shock waves that can rupture internal organs in fish and damage the auditory systems of marine mammals.

Bartholomew says that while some species may attempt to move away from high-activity zones, that displacement comes at a cost. “Whales and dolphins may temporarily move out of areas where there is significant naval sonar activity. Their short-term behavior in the region may be negatively affected," he says. "Overall, they will likely be fine. The most likely outcome is temporary displacement from areas with extensive sonar use.”

In a confined corridor like the strait, even temporary displacement can interfere with feeding patterns and habitat use, turning short-term disruption into longer-term ecological stress.

“Slow-Flush” Nature

The Arabian Gulf is uniquely vulnerable, because it does not easily reset.

It is what scientists describe as a “slow-flush” sea, taking between two and five years to fully exchange its waters. That means contaminants—whether from oil, fuel, or debris—can persist long after the initial event, spreading across both surface and seabed ecosystems.

Bartholomew warns that even a single major spill could have far-reaching consequences: “A major oil spill in the Strait of Hormuz could contaminate beaches and severely affect turtle nesting sites, including islands such as the Sir Bu Nair.”

“Oil spills can kill adult turtles and sea snakes and damage nesting habitats. They could also harm marine mammals such as the Indo-Pacific humpback dolphins in Musandam waters [near the strait] and the Indo-Pacific bottlenose dolphins, as well as kill seabirds.”

The danger is not limited to the surface. Whale sharks that migrate seasonally into the Gulf through the Strait of Hormuz, particularly between May and September, are vulnerable to floating oil because they feed near the surface.

Bartholomew adds: “Although oil generally floats, storms and high waves can mix it to deeper depths, which could negatively affect coral in the strait’s region, where coral diversity is the highest in the Gulf, especially on the Iranian side.”

Surface pollution can also alter animal behavior in unexpected ways. Oil slicks create shaded areas on the water’s surface, similar to fish-aggregating devices, which naturally attract small fish. This can draw other animals—including turtles, sharks, and marine birds—into contaminated zones, exposing them to toxins and increasing the risk of ingestion or coating.

In shallow coastal zones, where biodiversity is concentrated, even small disruptions can cascade through the ecosystem. Recovery is often slow, if it happens at all.

Loss of Light

For dugongs, the threat is less visible but no less severe. These animals depend on seagrass meadows, which require sunlight to grow.

Adam says that the presence of vessels introduces multiple pressures at once, from pollution to physical disruption of the seabed. One of the most immediate effects is the loss of light: “The oil slicks that remain on the surface block sunlight and prevent photosynthesis, which is essential for seagrass meadows,” he explains.

In shallow waters, where marine life is most concentrated, damage to the seabed is difficult to reverse. And oil spills near the coast can potentially harm mangroves if currents push the slicks towards the shore.

What appears to be temporary disruption on the surface can translate into long-term habitat loss below it.

Unfolding in the Dark

The most critical failure, however, may be invisible. War does not just damage ecosystems, it disrupts the ability to observe them by cutting off access to the coastline and the sea at the exact moment when monitoring is most needed.

Adam says this creates a gap in understanding that can last long after the conflict itself. “Fieldwork becomes impossible," he says. “This constitutes a major obstacle to conducting medium-term scientific studies, particularly for understanding ecosystem variations over several months or years.”

Even the tools designed to monitor marine life begin to fail under these conditions. Passive acoustic monitoring systems can be damaged or lost, leaving scientists in the dark about the true extent of the damage.