Latest news with #TimSmyth
Indian Express
13-06-2025
- Science
- Indian Express
Global oceans are darkening, disrupting life beneath the surface: Study
Climate change is not only causing irreversible damage to the green cover, they are equally impacting marine life. A new study seems to suggest that more than one-fifth of the global ocean has considerably darkened in the last two decades. This alarming state of the oceans has been brought to light by the study, Darkening of the Global Ocean, conducted by researchers from University of Plymouth. The study by Dr Thomas Davies, Professor Tim Smyth, and team, suggest that ocean darkening at this scale is not only the latest ecological crisis, but one that comes with grave implications for marine life and overall planetary health. Darkening of the ocean is essentially shrinking of the photic zones or those layers of water where sunlight can pass and induce the process of photosynthesis which is key to all biological processes. The photic layers can go down to about 200 meters and they also act as a base for nearly 90 per cent of the world's marine life. This layer is responsible for increasing the productivity of the ocean which also involves regulating climate and even supporting global fisheries or related activities. As part of the study, Davies and Smyth used satellite data along with sophisticated modelling techniques to analyse changes in how the oceans have absorbed light in the last two decades. The duo tracked the changes using the diffuse attenuation coefficient (Kd 490), a measure of how rapidly light fades as it passes through seawater. The finding of the study is critical as it indicates that between 2003 and 2022, nearly 21 per cent of the global ocean experienced darkening. While nine per cent (equivalent to the area of the continent of Africa) saw a decline in photic zone depth greater than 50 metres, 2.6 per cent saw reduction of over 100 metres. Even though the study states massive loss of light, around the same two decade-span, a considerable part of the global ocean has actually become lighter. This shows that the predictability of ocean darkening is not even across all waterways. The North Sea, the eastern UK coastline, and the Arctic have lost more light than any other regions, while there have even been small areas (e.g. regions of the English Channel) that have had more light. These patterns are the result of varying environmental conditions in different regions which includes varied rainfall, land use, and ocean currents. However, the most prominent darkening was observed in the open ocean, particularly in climate-sensitive zones like the Arctic, Antarctic, and Gulf Stream region. Coastal areas like the Baltic Sea have also lost photic depth because of erosion of sediments and nutrients from lands. Also Read | Deep sea chronicles: Why the mating of anglerfish is one of nature's extraordinary love stories In coastal zones, darkening is usually due to higher runoff of agricultural nutrients, organic matter, and sediments into the ocean with rain which directly promotes algal blooms that block light. In the open ocean, the likely causes are changes in plankton dynamics, increase in sea surface temperature and changes in ocean circulation. 'There has been research showing how the surface of the ocean has changed colour over the last 20 years, potentially as a result of changes in plankton communities. But our results provide evidence that such changes cause widespread darkening that reduces the amount of ocean available for animals that rely on the sun and the moon for their survival and reproduction,' Davies explained. 'We also rely on the ocean and its photic zones for the air we breathe, the fish we eat, our ability to fight climate change, and for the general health and wellbeing of the planet. Taking all of that into account, our findings represent genuine cause for concern', he added. The contraction of photic zones may lead to fundamental shifts in marine ecosystems. Those species that use sunlight and moonlight cues to feed, move, hide, and reproduce will be competing for shallower zones. This might upset marine food webs that are already working hard against an ecosystem with minimal fishing activity. Smyth, who is the head of Science for Marine Biogeochemistry and Observations at the Plymouth Marine Laboratory, highlighted the ecological danger. 'The ocean is far more dynamic than it is often given credit for. For example, we know the light levels within the water column vary massively over any 24-hour period, and animals whose behaviour is directly influenced by light are far more sensitive to its processes and change. If the photic zone is reducing by around 50 m in large swathes of the ocean, animals that need light will be forced closer to the surface where they will have to compete for food and the other resources they need. That could bring about fundamental changes in the entire marine ecosystem,' Smyth said. The indicator species used in this experiment was Calanus copepods, a highly photosensitive zooplankton. These animals are at the center of the marine food chain and use very faint light cues from the Sun and Moon for vertical migrations during the day and various other behaviours. Also Read | Study: Only 24% present-day glaciers will remain if world gets warmer by 2.7°C The study infers ocean darkening as maybe one of the biggest global habitat loss cases ever in recent memory. Animals depending on light are being constrained to narrow vertical spaces, increasing predation and greater competition for resources. In due course, this may kill biodiversity, disrupt oceanic carbon cycling, oxygen production, and ocean buffering against climate change. (This article has been curated by Prachi Mishra, who is an intern with The Indian Express)
The Guardian
05-06-2025
- Science
- The Guardian
Into the photic zone: does a darkening ocean threaten marine life?
Vast areas of the ocean are getting darker, according to research based on satellite imaging. Marine ecosystems are governed by faint light changes – from mass nightly migrations to coral spawning cycles – so what happens when that light begins to fade? Ian Sample talks to Prof Tim Smyth from the Plymouth Marine Laboratory about why this darkening is happening and how life in the 'photic zone' – the sunlit upper layer that is home to 90% of marine organisms – could be profoundly affected
Yahoo
01-06-2025
- Health
- Yahoo
The ocean is getting even darker
The ocean is darkening. Researchers say more than a fifth of the planet's ocean — which makes up 70 percent of the surface of the Earth — has been subject to the darkening process over the course of the past two decades. It occurs following changes in the optical properties of the ocean that reduce the depth of its photic zones, the surface layers of the ocean that receive sunlight and moonlight, where 90 percent of marine life live. The consequences of continued shifts could be concerning — both for sea creatures and humans alike. Although there's much we don't know. A stunning 80 percent of the ocean remains unobserved and unexplored. 'If the photic zone is reducing by around 50 meters [55 yards} in large swathes of the ocean, animals that need light will be forced closer to the surface where they will have to compete for food and the other resources they need. That could bring about fundamental changes in the entire marine ecosystem,' Tim Smyth, the head of science for marine biogeochemistry and observations at the Plymouth Marine Laboratory, warned in a statement. Smyth was one of the co-authors of the study, which was published recently in the journal Global Change Biology. Possible ecosystem changes and animals moving closer to the surface could also be worrying for humans, who rely on the ocean for recreation, transport, and food. The change could also upset the availability of smaller prey, including brown shrimp, tuna, and other pelagic fish. In addition, it could send predators into new waters that are closer to shore, and potentially to swimmers. That's already happening thanks to climate change, as sharks follow schools of menhaden along the East Coast. The precise implications of changes, however, are 'not wholly clear' at this point, and 10 percent of the ocean has become lighter during the same time period. Using data from NASA's Ocean Color Web satellite, which breaks the global ocean down into a series of nine kilometer (5.5 mile) pixels, they were able to see changes on the ocean's surface. The authors developed an algorithm to measure light in seawater and tell them the depth of the photic zone in each location. They also relied on models to look closer at changes during daylight and moonlight conditions, determining that changes in photic zone depth at night were small compared to the daytime. The researchers found that more than nine percent of the ocean had seen its lit zones reduced by more than 50 meters, and just under three percent saw them reduced by more than 100 meters (109 yards). Coastal changes are likely due to multiple factors, including nutrients entering the water because of increased rainfall and agricultural runoff. Climate change is also leading to heavier rain events. In the open ocean, harmful algal blooms spurred by climate-change-driven sea surface temperatures have helped to block light. The most prominent changes were observed around the poles and the top of the Gulf Stream near Florida. Florida has seen multiple major harmful algae blooms in recent years, and a record bloom is headed for South Florida this summer. The most prominent changes in photic zone depth in the open ocean were observed at the top of the Gulf Stream, and around both the Arctic and Antarctic, areas of the planet experiencing the most pronounced shifts as a result of climate change. Darkening was also widespread in the Baltic Sea, which borders northern Europe and where rainfall on land brings sediment and nutrients into the sea, stimulating phytoplankton growth. Phytoplankton are microscopic marine algae and the base of several food webs. 'There has been research showing how the surface of the ocean has changed color over the last 20 years, potentially as a result of changes in plankton communities. But our results provide evidence that such changes cause widespread darkening that reduces the amount of ocean available for animals that rely on the sun and the moon for their survival and reproduction,' said Dr. Thomas Davies, an associate professor of marine conservation at the University of Plymouth. 'We also rely on the ocean and its photic zones for the air we breathe, the fish we eat, our ability to fight climate change, and for the general health and wellbeing of the planet. Taking all of that into account, our findings represent genuine cause for concern,' he added.
Yahoo
31-05-2025
- Health
- Yahoo
The Ocean Is Getting Darker, Threatening All That Lives Within
Almost all life in the ocean depends on the upper waters where sunlight filters in, known as the photic zone – but new research suggests this narrow window of valuable marine light is shrinking in oceans worldwide. In the past 20 years, marine scientists have found, more than a fifth of our oceans have been growing darker. Thomas Davies, a marine biologist from the University of Plymouth, and Tim Smyth, a marine biogeochemist from the University of Exeter, noticed that despite growing concerns from scientists about ocean darkening, nobody had really quantified its extent. "There has been research showing how the surface of the ocean has changed color over the last 20 years, potentially as a result of changes in plankton communities," Davies says. "Our results provide evidence that such changes cause widespread darkening that reduces the amount of ocean available for animals that rely on the Sun and the Moon for their survival and reproduction." Pairing NASA satellite data from 2003 to 2022 with numerical modeling, the duo has uncovered a pattern of the photic zone depth – which inherently constrains the habitat for most ocean life – shrinking across the years. The photic zone is the topmost layer of the ocean, where light from the Sun (including that reflected off the Moon) permeates the water. All marine organisms that photosynthesize – seagrasses, kelps, and most essential of all, phytoplanktons – must live in the shallower parts of this layer to harness the Sun's energy. So the many other organisms that depend on these primary producers – like corals, crustaceans, fish, and marine mammals – hang out in the photic zone too. The study found in nearly 10 percent of the world's oceans, the depth of the photic zone has shrunk by more than 50 meters (164 feet). This means that three-dimensional habitat has become a lot smaller, which leads to greater competition for resources. Even worse, in 2.6 percent of the ocean, the photic zone has reduced by more than 100 meters. "The ocean is far more dynamic than it is often given credit for. For example, we know the light levels within the water column vary massively over any 24-hour period, and animals whose behavior is directly influenced by light are far more sensitive to its processes and change," says Smyth. "If the photic zone is reducing by around 50 meters in large swathes of the ocean, animals that need light will be forced closer to the surface, where they will have to compete for food and the other resources they need. That could bring about fundamental changes in the entire marine ecosystem." A few factors affect the depth of the photic zone. Light that hits the ocean in a vertical nosedive, like equatorial rays shining in the middle of the day, can penetrate further into the water, with fewer photons reflecting off the surface. And the less resistance those plunging photons encounter, in the form of suspended sediment and organic matter, the further they can dive. That's why, in clear tropical waters, light can penetrate up to 80 meters deep. When entering the water at an angle, however, more light reflects off the surface, and photons that do break the surface have to travel farther on their way down. This results in a much narrower photic zone at the poles – less than 10 meters deep in some places. This may partially explain why some of the most prominent changes were seen in the photic zones of the Arctic and Antarctic. But sediment and other suspended matter, like algal blooms, make the water more opaque, affecting the depths that light can reach. This is what Davies and Smyth suspect is darkening the world's waters in recent decades. "A combination of nutrient, organic material, and sediment loading near the coasts and changes in global ocean circulation are probable causes of increases in primary and secondary productivity that have reduced light penetration into surface waters," they write in their research paper. In extreme cases, like the recent algal blooms across Australia's Great Southern Reef, a lack of light can lead to mass mortality events. But the world's photic zones aren't only shrinking near the coast, where we would expect excess runoff from human activities to cloud the waters, as is evident in the Baltic Sea and the eastern coasts of England and Scotland. Darkening was also prominent in the Gulf Stream and the poles, where climate change is rapidly changing the natural systems. "We also rely on the ocean and its photic zones for the air we breathe, the fish we eat, our ability to fight climate change, and for the general health and wellbeing of the planet," Davies says. "Taking all of that into account, our findings represent genuine cause for concern." This research was published in Global Change Biology. Your Salad Could Be Carrying Microplastics From Soil Into Your Body UN Warns: High Odds We'll Exceed 1.5°C Temp Rise by 2029 Earth's Crust Is Hiding Vast Reserves of Hydrogen – Here's How We Can Find It
The Independent
30-05-2025
- Health
- The Independent
The ocean is changing colour – why it's a threat to marine life
A recent study reveals that over a fifth of the world's ocean has darkened in the last two decades, reducing the surface layers of the sea that receive light, known as photic zones, and where most marine life exists. The darkening is attributed to factors like increased rainfall, agricultural runoff, harmful algal blooms, and climate change, with significant changes observed near the poles, the Gulf Stream, and the Baltic Sea. Reduced photic zones may force marine animals closer to the surface, increasing competition for resources and potentially altering the entire marine ecosystem, according to Tim Smyth of Plymouth Marine Laboratory. Changes in the ocean's photic zones could impact human activities such as recreation, transport, and food supply, potentially affecting the availability of prey and driving predators closer to shore. Researchers used data from NASA's Ocean Color Web satellite and developed an algorithm to measure light in seawater, finding that over 9% of the ocean saw its lit zones reduced by more than 50 meters.
