The geographic position of the Strait of Hormuz makes it a crucial location not only from a political but also an ecological point of view.
Not far from the stranded ships in the Persian Gulf lies an ecological wonder. The hotly contested Strait of Hormuz is home to dolphins and the region’s most diverse coral population, an underwater world that scientists say may be in danger due to the conflict surrounding it.
Although Iran at one point announced the reopening of the strait during a temporary ceasefire, around 2,000 ships remained stuck in the Gulf during that period, transporting a total of around 21 billion liters of oil. Since the start of the war, there have been at least 16 attacks on ships in the Persian Gulf and near the Strait of Hormuz.
Nina Noelle, a spokeswoman for Greenpeace, an organization focused on environmental issues, tells CNN that through continuous monitoring, the group’s researchers “regularly detect oil slicks in the region,” including one linked to the Iranian ship Shahid Bagheri, which was struck by a US warplane in early March.
According to Greenpeace, the ship was spilling oil “near the Khuran Strait and posed a potential risk to nearby protected wetlands.” The Strait of Khuran is a narrower passage that runs north of the Strait of Hormuz.
The geographic position of the Strait of Hormuz makes it a crucial location not only from a political but also an ecological point of view — it is located in a transition area between the deep and cold Gulf of Oman and the shallow and warm Persian Gulf. Currents arriving from the Gulf of Oman carry nutrients and larvae that feed blooming plankton and coral reefs, while deeper waters attract reef fish and migratory whale sharks that pass through seasonally.
In more peaceful times, diving and dolphin watching in Musandam province, a part of Oman that borders the strait, was a magnet for tourism. The strait provides nesting sites for sea turtles and the Oman coast is home to critically endangered, non-migratory Arabian humpback whales, with dugongs and sea snakes in the surrounding waters.
As the conflict drags on, scientists are increasingly concerned about the impact of oil spills on the region’s animals.
“Many of the compounds found in crude oil affect heart function and respiration,” says Martin Grosell, professor and chair of the department of marine biology and ecology at the University of Miami’s Rosenstiel School of Marine, Atmospheric and Earth Sciences. “Prolonged exposure to petroleum will lead to overexertion of the stress response, which suppresses immune function, making animals more susceptible to infections and other types of environmental insults.”
Crude oil also disrupts animals’ nervous systems, Grosell adds, impairing their senses and their ability to navigate, process information and correctly orient themselves in their environment. This affects how they respond to predators and find prey, meaning harm done to animals can have repercussions across the entire ecosystem.
What animals live in the strait?
The Strait of Hormuz, a narrow passage between Iran in the north and Oman and the United Arab Emirates in the south, is located at the mouth of the Persian Gulf. Aaron Bartholomew, a biology professor at the American University of Sharjah in the United Arab Emirates (UAE) who has conducted field research throughout the region, describes the strait as the ecological crown of the Gulf.
“The Strait of Hormuz is known for having the greatest diversity and one of the largest coral covers in the entire Gulf,” says Bartholomew. The richest concentrations are on the Iranian side of the strait, as well as along parts of the southern Gulf coast. Coral reefs in the area have been hit hard by bleaching events linked to rising ocean temperatures, but have resisted, while corals elsewhere have not.
Bartholomew explains that conditions in the Gulf push marine life to its physiological limits. “We have very, very hot temperatures during the summer and surprisingly cold temperatures in the winter,” he says. “We also have high salinity due to all the evaporation from the Gulf,” he adds, referring to the high concentrations of dissolved salts in the water that typically cause ecological damage.
In most of the world’s oceans, such extremes would be lethal to corals. Here, conditions have produced “arguably the toughest corals in the world,” says Bartholomew. According to him, the region’s corals are important to researchers who are actively studying them as a model for how they can survive the warmer and more volatile oceans that the man-made climate crisis will bring.
“Corals are the most biodiverse ecosystem in the oceans and support a wide variety of fish and invertebrate species,” adds Bartholomew. “They’re certainly important for fishing. They’re also important for tourism.”
In addition to the reefs, the waters around the strait are home to a dense and varied community of animals. Indo-Pacific humpback dolphins and Indo-Pacific bottlenose dolphins live along the Musandam Peninsula in northern Oman. Bartholomew said he is concerned about these mammals, which need to come to the surface to breathe.
Offshore islands such as Sir Bani Yas Island, situated between Iran and the United Arab Emirates, serve as nesting grounds for green and hawksbill sea turtles. “It is well documented that oil spills in UAE waters cause the mortality of turtles, which essentially die in the oil spill itself and then wash ashore,” says Bartholomew.
Sea snakes also occupy the shallow coastal waters of the UAE. Whale sharks pass through here seasonally, following mackerel tuna, which spawn in Qatar’s oil-rich offshore waters. Because fishing is prohibited near the platforms, these waters have become an accidental marine protected zone. “Whale sharks follow them and eat the eggs of spawning mackerel tuna,” explains Bartholomew.
There are also mangroves “along the southern coast, particularly in the emirate of Abu Dhabi, but also in the northern emirates such as Ras Al Khaimah and Umm Al Quwain,” says Bartholomew. The gray mangroves, or Avicennia marinaare abundant in the area and are typically resistant to oil spills, “as long as the so-called pneumatophores are not covered,” says Bartholomew. Pneumatophores are exposed root structures that rise and act as snorkels, reaching above the surface to transport oxygen to the underground roots of the mangrove tree. For this reason, mangroves “can generally survive oil spills, but if their pneumatophores are covered, they are affected and may die.”
Further from the strait, in the shallow seagrass meadows west of Abu Dhabi and south of Qatar, lives the world’s second largest population of dugongs, a mammal closely related to manatees. “We have some of the largest continuous seagrass meadows in the world there,” explains Bartholomew. Although dugongs are currently protected from conflict in the strait, Bartholomew notes that a spill reaching their coastal waters would pose a serious threat.
What does oil do to animals?
Grosell, of the University of Miami, spent 15 years studying the impacts of oil on marine life following the 2010 Deepwater Horizon disaster in the Gulf of Mexico.
“You’ve heard that oil and water don’t mix, but that’s not true,” says Grosell.
Wave action on the water’s surface can break the oil into smaller droplets, which sink to the depths of the ocean. “Crude oil, or even refined oil, is a very complex mixture of thousands of chemicals.” Some toxic chemicals are also released from the oil and enter the water column, the ocean habitat that extends from the surface to the sea floor.
When chemicals from petroleum dissolve in the water column, water-breathing animals such as fish absorb them through their gills and corals absorb them directly through their tissues. Oil found at the surface is harmful to animals that come to the surface to breathe, such as dolphins, sea turtles and sea snakes.
For both air and water breathers, many of the chemicals in crude oil target the heart and respiratory function, the immune system, the sensory system and the central nervous system.
“Some of these compounds found in crude oil affect sensory systems: the ability to smell things, the ability to see things and the ability to detect vibrations in the environment,” says Grosell. Corals face similar effects, as they “capture prey from the water through thin tentacles and would be exposed to chemicals found in the water column during oil contamination.”
“There are also reports of effects on the central nervous system,” which affect the animals’ ability to process data from their sensory systems. Research into oil spills in the Gulf of Mexico has also shown that exposure to oil can reduce fish reproduction, adds Grosell.
As a whole, these factors can affect how animals make decisions and the length of their lives. The chemical effects of crude oil on animals may be less lethal to them than being directly suffocated by oil in a spill, “but in a complex environment where you are constantly balancing obtaining resources and avoiding falling victim to prey, these effects on decision-making, or on sensory systems, or even subtle effects on the heart, can lead to shorter lives for many of these animals.”
Because of the complexities of predator-prey relationships, the impact on individual organisms ripples across the entire ecosystem, Grosell says. The researcher considers that, as more ships remain in the strait, more oil spills are likely to occur, worsening the negative environmental impact.
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