The researchers conducted experiments ranging from locking prey species in cages to putting “squid” to measure how many predators they were able to bite depending on the temperature of the water in which they lived. It has long been observed that marine predators are more vicious in tropical waters, but with climate change leading to global warming, researchers at the Smithsonian Environmental Research Center (SERC) wanted to study the effects this could have in the future. . Usually, temperature changes that lead to major changes in marine ecosystems occur over millennia, not decades. “It took us thousands of years to reach this state and we are suddenly raising the temperature to a much higher rate,” Gail Ashton, lead author of the new report and marine biologist with SERC, said in a press release. “And we do not really know the consequences of this temperature rise.” An international team of researchers led by SERC conducted experiments on marine predators and prey at 36 locations on the Atlantic and Pacific coasts of the United States to study how these species react at different temperatures, hoping to predict what a warmer ocean would bring. The results, published Friday in the journal Science, found that predation would increase in intensity as the oceans warm, with unknown – but certainly far-reaching – effects on other species and the ocean as a whole. “Warmer waters tend to favor animals high in the food chain, which become more active and need more food, and it is their prey that pays for this increased activity,” said Emmett Duffy, director of Smithsonian’s Marine Global. Earth Observatory Observatory (MarineGEO) and co-author of the study, said in a statement. “This suggests that warming seas could cause major changes in the lives of vulnerable seabed habitats.” To get their results, the researchers conducted three specific experiments at each of the sites to test how strong the predators’ response was to different waters. The sites stretched north to Alaska and south to Tierra del Fuego, an archipelago in the lower reaches of South America. First, the researchers confirmed that warmer waters were associated with higher predation. In this experiment, the researchers created an attractive delight for predators, inventing a “squid pop” for its resemblance to the “cake pop” dessert. These cut pieces of dried squid on a stick were left under water to attract fish, and then the researchers checked again in an hour to see how many of the “popping squid” were left. The results were clear: in warmer waters, many more predators came out to bite, while in waters below 20 degrees Celsius, almost zero prey was recorded. “This temperature limit represents an ecological turning point in these coastal marine ecosystems, above which the intensity of predation is increasing,” said Amy Freestone, co-author and associate professor of biology at Temple University. “With climate change, more coastal waters will cross this turning point or become even hotter, fundamentally changing the way these ecosystems work.” Once this was found, the researchers placed the prey in different places of availability for the predators to see how the predator affected their growth and numbers in different waters. In one experiment, they let prey such as underwater invertebrates and mosses grow on plastic panels for three months, some protected from caged predators and others left exposed to any potential fish that wanted a snack. In the last experiment, the researchers placed protective cages around all their prey for 10 weeks and then released half of them for another two weeks to test what happened when they grew up safely and then exposed to predators. These experiments were performed in water with drastically changing temperatures and the results confirmed what the researchers had suspected would happen: the levels of prey species would plummet into warmer waters if left uncovered and unprotected. But in colder waters, it did not matter whether the prey was protected or not – prey levels remained very low regardless of this, reinforcing that prey was less active in colder waters. But what does this really mean for the overall ecosystem as more and more water gets warmer? Researchers say total marine ecosystems could become more “top-down” as the waters warm, with predators controlling the oceans instead of balancing with them. “Such large-scale changes in top-down control could have far-reaching consequences, given the key role of species interactions in maintaining ecosystem structure, diversity, biogeochemical processes and providing critical ecosystem services to human communities.” , the study said. . For example, some of the most commonly consumed species of prey in areas with higher prey, such as tunicates, play an important role in the overall ecosystem. The tunics filter the water and provide “corners and crevices” for other sea creatures to live in, the press release explains. “As predators change, some species will be winners and some will be lost,” said Greg Ruiz, head of the SERC Marine Invasion Research Laboratory and co-author of the study. “Some will defend themselves. others will be vulnerable. “But we do not know exactly how this will happen.” Although these issues have been measured in smaller studies in the past, this is one of the largest to look at the larger picture of how temperature affects these levels of predation. The researchers observed that due to the different levels of marine species in different parts of the ocean, some of the results may have been affected by these different biomass levels. “More broadly, site variation underscores the need for high reproduction and broad coverage for thorough evaluation of both regional and global standards,” the study said. “Our results suggest that climate change may have predictable effects on the regulation of communities near the coastline along the world’s shores.”
