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Scientists have recognised for some years that light pollution from buildings, vehicles and streetlights is a growing phenomenon that impacts on the behaviour and success of many animals including migrating birds, hunting bats and the moths they try to capture.

As the human population grows the problem is due to worsen and even remote coastal areas are now being affected by civilization’s tell-tale glow-in-the-sky. Turtles, disoriented as they return to their nesting beaches, or confused hatchlings struggling to find the sea, are iconic examples. Now scientists from PMLand the University of Exeter have asked the questions, if turtles are being affected what about other marine life, and how does that compare to other known stressors, such as climate change?

As part of Charlotte Underwood’s Master of Science project, the group set up a series of laboratory experiments to determine whether the less well known, but highly important inhabitants of the seashore were also affected. Using the dogwhelk (Nucella lapillus), a key seashore species that modulates biodiversity and community structure of our coasts, Charlotte kept one group of dogwhelks  in artificially-lit night sky conditions, while a control group experienced a more natural night/day cycle, and the results were clear. Those dogwhelks kept under night-time lighting sought out refuges far less than those under ‘normal’ conditions, so were exposed for much longer, spent longer seeking food and so were thought to be energetically deprived, and potentially at risk from predation if they had exhibited these behaviours in nature. These individuals continued to respond to and handle prey whether they could ‘smell’ predators in their surroundings or not. The animals that had not been used to night-time lighting, on the other hand, were more likely to respond to prey under night time light even if scent cues were present; this might indicate an opportunistic approach towards using vision instead of smell under illuminated conditions at night to evaluate predator risk. This study, published in the British Ecological Society’s Journal of Animal Ecology, therefore shows, for the first time, that night time light changes species interactions at the heart of the way in which natural food chains work, raising concern about how generalised these impacts may be for natural marine wildlife.
 
Dr Thomas Davies from the University of Exeter’s Environment and Sustainability Institute based on the Penryn Campus, Cornwall, highlighted how historically overlooked the impacts of light pollution on coastal ecosystems has been, saying: “There has been a surge of research into the impacts of artificial lighting on land animals and plants over the last six years, but the influence on coastal animals of lights from harbours, marinas, piers and promenades has received very little attention. Understanding how to manage ecosystems to improve biodiversity gains is as important in the built marine environment as it is in our city parks, gardens, streets, rivers and canals. This study highlights that night-time lighting in coastal cities can impact biodiversity on rocky shores popular with beachgoers that enjoy the diversity of life they offer year round.”

Dogwhelks are far from unimportant along rocky coasts, where they can occur in dense aggregations, and play a key role in the ecological balance, feeding on barnacles, limpets and mussels. Disturbing these balances can have major ramifications across habitats and up food webs.

PML senior ecologist Dr Ana Queirós who co-led the study highlighted that: “because we designed this study replicating experiments where we had measured the impacts of climate change, we have here the first evidence that night time lighting can impact marine wildlife in coastal communities to a similar degree, and in a much more generalised way than we thought. Who eats whom and how, the species interactions we measured, are the inner workings of food webs. So it is not just nesting turtles and hatchlings on the beaches that are affected: it is the whole way in which shore food chain works. We must be cautious with generalisations, but we have been slow in recognising night time light as a worldwide marine issue. However, unlike for climate change, the solution for night time light pollution is well within our reach, as restricting use of lights to specific colours can much limit their negative impacts on wildlife, as has been shown in terrestrial studies. We should be acting on coastal light pollution immediately, because this time, we can actually fix the problem.”

Image above right: Dogwhelks by night ©Kelvin Boot, PML.