Amman — An invisible environmental threat could alter the future of marine life in the Gulf of Aqaba, as recent scientific studies have revealed a decline in the penetration of sunlight across large areas of the world’s seas and oceans, a phenomenon known as “ocean darkening.”
The phenomenon could affect the ability of marine ecosystems to perform vital functions.
Experts have warned that declining light levels could affect the reproduction and behavior of marine organisms and their food relationships, while weakening coral reefs’ ability to recover from heatwaves and pollution, without necessarily producing immediate signs of ecosystem deterioration.
Although scientific studies indicate that around one-fifth of the world’s oceans has become darker, there is currently no scientific evidence confirming that the phenomenon is occurring in the Gulf of Aqaba, given the limited availability of long-term measurements of light penetration into its deeper waters.
This highlights the importance of moving beyond traditional water-quality indicators to monitor changes that could affect the vital functions of marine organisms, experts told Al-Ghad.
Traditional Water-Quality Indicators
Dr. Raed Al-Manasrah, a professor of marine physics at the University of Jordan, said the Gulf of Aqaba could gradually lose some of its transparency without this necessarily being detected by traditional water-quality indicators.
Such indicators generally monitor major changes, while light penetration may gradually decline as a result of fine particles or dissolved organic matter. This makes direct measurements of light levels increasingly important, he said.
Speaking to Al-Ghad, Al-Manasrah noted that marine currents can transport turbidity to areas far from its original sources, potentially threatening coral reefs that have not been directly exposed to pollution.
Fine particles can reach such reefs from other areas, although the scale of the threat depends on the concentration of those particles after they disperse and become diluted in the water. Determining this requires field studies specifically focused on the Gulf of Aqaba.
He said mixing between different layers of water could also indirectly contribute to blocking light from reaching deeper waters, even without an increase in pollution.
The process may bring nutrients from deeper waters toward the surface, stimulating the growth of phytoplankton and reducing the amount of light reaching lower layers without introducing new pollutants into the marine environment.
Al-Manasrah ruled out the possibility that sudden floods alone could cause a lasting change in the Gulf’s underwater light environment, explaining that their effects are generally temporary and localized, particularly near wadi outlets.
However, as sediments settle over time, the frequency and intensity of floods warrant continued monitoring, he said.
He stressed that it is impossible to determine whether the amount of light currently reaching the Gulf’s deeper waters remains at the same levels recorded 20 years ago.
Satellite imagery can monitor the surface layers of the water, while measurements of light at greater depths remain limited. This, he said, calls for the establishment of a long-term monitoring program.
Al-Manasrah also did not rule out the possibility that changes in water movement and temperatures could become a threat to marine life by reducing light penetration, even without an increase in pollution levels.
Such changes can affect the distribution of nutrients and plankton, potentially reducing the amount of light reaching deeper waters and adding another source of stress to coral reefs alongside the stress caused by rising temperatures.
He explained that “ocean darkening” is associated with an exponential decline in light intensity as depth increases, with the process accelerating as concentrations of suspended particles, plankton and dissolved substances rise.
The phenomenon is defined as a reduction in the depth to which sufficient light penetrates to support marine life and vital biological processes.
Recent studies indicate that approximately one-fifth of the world’s ocean area has become darker. However, Al-Manasrah stressed that these findings cannot be applied to the Gulf of Aqaba without conducting measurements specific to the region.
Ecosystem Health
Biodiversity specialist Ihab Eid warned that coral reefs could become less suitable habitats for the reproduction of some marine organisms as lighting conditions change, even if the reefs themselves remain alive.
He attributed this to the fact that coral reef survival alone is not enough to determine the health of an ecosystem and the habitats it provides. These habitats depend on precise conditions involving light, temperature and water quality.
Speaking to Al-Ghad, Eid said that any sustained change in these conditions could affect reefs’ ability to support vital biological processes, including reproduction, larval development and the stability of small marine organisms.
He explained that reduced light reaching coral reefs affects the activity of symbiotic algae living within their tissues, which provide corals with a significant portion of their nutritional needs through photosynthesis.
This could reduce the functional efficiency of coral reefs and weaken their ability to provide suitable conditions for some of the organisms that depend on them.
Eid stressed that light in the marine environment is not merely a source of energy; it also acts as a natural biological clock that regulates the behavior of many marine organisms.
Many species rely on daily and seasonal changes in light intensity, as well as lunar cycles, to determine the timing of reproduction, daily activity and vertical movement through the water column.
When the amount of light reaching certain depths changes, environmental signals used by some organisms may also change. This could disrupt the timing of reproduction or alter daily movement and migration patterns, affecting the natural synchronization between marine species.
Eid warned that declining light levels could limit the ability of marine habitats to recover following heatwaves and pollution incidents, even after the pressures that caused the damage have disappeared.
This is an important aspect of understanding the relationship between “ocean darkening” and the resilience and recovery capacity of marine ecosystems.
He added that coral reef recovery following heatwaves or pollution incidents does not depend solely on removing the source of damage. Suitable environmental conditions are also required to restore biological processes, growth and reproduction.
When reduced light penetration persists because of turbidity or suspended matter in the water, symbiotic algae may become less capable of producing the energy needed by corals.
This can affect coral growth, tissue regeneration and the restoration of normal functions.
Scientific studies have shown that coral reefs recovered more successfully after thermal bleaching events in areas with less turbid water compared with locations experiencing higher levels of turbidity, Eid said.
He noted that stable numbers of marine organisms do not necessarily mean that ecological relationships between them have remained unchanged.
Many fish and other marine organisms depend on light to detect prey, avoid predators and determine when to feed or seek shelter.
According to Eid, reduced light could shorten the distance over which visually oriented predators can detect their prey, while other species that rely on different senses or are better adapted to low-light conditions may benefit.
These changes could affect predation rates, activity periods and patterns of habitat use without necessarily producing immediate changes in species populations.
Jordan has established marine environmental protection frameworks in the Gulf of Aqaba, most notably the Aqaba Marine Reserve and its 2022–2026 management plan, which focuses on protecting coral reefs and marine habitats, improving their management and monitoring environmental pressures affecting them, Eid said.
He explained that protection programs are not limited to studying living ecosystems but also include monitoring physical characteristics, including water quality.
Strategies to reduce pollution are also being implemented across the Gulf of Aqaba, he added.
Eid also highlighted the Gulf’s environmental characteristics. The Gulf is a semi-enclosed body of water with no river outlets that would increase water turbidity, contributing to its high levels of transparency.
Under suitable conditions, it is therefore possible to see depths exceeding 30 meters with the naked eye.
To reduce the risks associated with “ocean darkening,” Eid called for continued monitoring programs, stronger effective management and early preparedness for emerging environmental risks, particularly in an area of exceptional ecological and scientific importance such as the Gulf of Aqaba, known as the “divers’ paradise.”
Source: Al-Ghad
