Illuminating Ocean Threats on Day Two of the World Ocean Summit

At the Economist Impact’s World Ocean Summit, which is currently underway in Tokyo (March 13th-14th), the impacts and challenges of mitigating pollution from shipping and plastics were a key part of discussions as delegates from across industry, policy and academia gathered for day two of the event.   

During the morning innovative sessions, PML’s Professor Tim Smyth drew attention to the less visible but increasingly concerning threat to marine ecosystems from artificial light at night (ALAN).  

As PML’s Head of Science for Marine Biogeochemistry and Observations, Professor Smyth’s presentation: “Satellite Seascapes: applying advanced technology to tackle marine and light pollution” explored how modern techniques in areas such as earth observation are helping scientists understand and assess these growing environmental challenges. 

Marine light pollution – artificial light from coastal developments, shipping, ports, offshore infrastructure, fisheries, and other sources – is dramatically altering the natural light environment in coastal areas. These artificial sources can illuminate marine environments up to 100 times brighter than natural moonlight, with profound consequences for species and ecosystems. 

Image: Prof Smyth presenting in the Innovation Showcase 

“We already know that artificial light is detected at around a quarter of the world’s coasts and will dramatically increase as coastal human populations more than double by the year 2060,” explains Professor Smyth.  

“It can have devastating potential effects on species found underwater and along the shoreline, fundamentally altering their behaviours and even their sensory systems.” 

From altered fish migration patterns to disrupted zooplankton behaviour, the impacts on marine life are wide-ranging and deeply concerning. Sea turtle hatchlings, which naturally orient toward the brightest horizon (typically moonlight reflecting off the ocean), become disoriented by artificial coastal lighting and may head inland instead of toward the sea. Predator-prey dynamics shift as illuminated areas give predators unnatural advantages. Coral reproduction, which relies on lunar cycle synchronization, faces disruption from artificial light interference. 

“Many marine species have evolved with predictable light changes that occur naturally throughout the day, across seasons and with the lunar cycle,” Prof. Smyth points out.  

“But light from coastal developments can scatter a long way out to sea and is spectrally quite different to moon and sunlight. The wavelengths penetrating the water column are fundamentally altering marine environments in ways we’re only just beginning to understand.” 

The scale of the problem is considerable. The groundbreaking PML-led global atlas of underwater ALAN reveals that at just one meter depth, approximately 1.9 million square kilometres of coastal ocean (about 3.1% of global Exclusive Economic Zones) are exposed to biologically significant levels of artificial light. This exposure remains substantial even deeper, affecting 1.6 million square kilometres at ten meters depth and 840,000 square kilometres at twenty meters. 

Image: An image showing the artificial light at night in Japan, from the global atlas of underwater ALAN

Furthermore, the growing adoption of white LED lighting presents particular concerns, as these emit more blue wavelength light that penetrates deeper into seawater compared to older lighting technologies.  

“Our ambition is to reduce light pollution and minimise its impacts on marine environment,” said Professor Smyth.“The great news is that it’s something that is in our ability to correct, but there needs to be a major shift in policy and industry, alongside increased broader awareness about the extent of the problem.”