When a heat wave hits land, animals and humans seek shade, water, or a cooler place. A similar response could be expected at sea. <\/p>\n\n\n\n
However, a new study conducted in the Gulf of Eilat reveals that, at least for some fish, the reality is completely different. <\/p>\n\n\n\n
The study, which was conducted over 5 years and followed 31 sea urchins in the Gulf of Eilat, was conducted by Dan Bez Golansky, a doctoral student in Professor Jonathan Belmaker's laboratory at Tel Aviv University.<\/p>\n\n\n\n
The focus of the study is on the tunas, one of the most prominent and important families of fish in the coral reef. Despite the increase in water temperature during marine heat waves, the fish studied hardly changed their behavioral patterns. They did not move to cooler depths, did not reduce activity, and did not abandon their habitats.<\/p>\n\n\n\n
At first glance, this could be seen as a sign of resilience, but the researchers believe that the lack of response may indicate significant vulnerability. "While logic would say they would seek cooler waters or reduce activity, the findings point to a much more complex reality, which may teach us a lot about the challenges that the climate crisis poses to marine ecosystems," explains Golansky.<\/p>\n\n\n\n
The heat waves that occur beneath the surface of the water<\/strong><\/p>\n\n\n\n In recent years, the phenomenon of marine heat waves, prolonged periods in which the temperature of the sea water is unusually higher than average, has been increasing. This is one of the most prominent phenomena related to the climate crisis, and it is currently being measured in many regions of the world, including the Gulf of Eilat.<\/p>\n\n\n\n For fish and other marine animals, whose body temperatures are directly affected by the temperature of their surroundings, warming water has immediate implications. As the water warms, the fish's metabolic rate increases and their energy requirements increase. In such a situation, many animals may try to conserve energy by moving to cooler water or changing their activity patterns.<\/p>\n\n\n\n The question that preoccupied the researchers was whether the tunas, considered one of the most important species for the functioning of the reef, also respond in a similar way.<\/p>\n\n\n\n The Gardeners of the Coral Reef<\/strong><\/p>\n\n\n\n Sea urchins play a central role in the coral reef ecosystem. They feed on algae that grow on the rocky substrate, preventing them from taking over the reef and damaging the corals. Due to their continuous activity, they are considered the reef's "gardeners," helping to maintain the delicate ecological balance between the corals and marine vegetation. <\/p>\n\n\n\n Several species of sea urchins can be found in the Gulf of Eilat, distinguished by their striking colors in shades of green, blue, and purple. Given their great importance to the health of the reef, researchers sought to understand how they cope with one of the main impacts of climate change.<\/p>\n\n\n\n Five years of tracking 31 fish<\/strong><\/p>\n\n\n\n To examine the behavior of the tunas under warming conditions, a long-term study was conducted on the reefs of the Gulf of Eilat. Over the course of five years, the researchers monitored 31 tunas from five different species. Acoustic telemetry technology was used for the study. <\/p>\n\n\n\n Tiny transmitters were implanted in the fish after they were collected from the reef during research dives conducted with a permit from the Israel Nature and Parks Authority. After a brief veterinary procedure and a recovery period in the laboratory, the fish were released back into the wild and continued their daily lives.<\/p>\n\n\n\n The transmitters provided researchers with continuous information about the swimming depth and activity level of each individual. <\/p>\n\n\n\n The data collected allowed us to examine fish behavior before, during, and after 12 different marine heat waves. The assumption was that during heat events, fish would choose to move to deeper, cooler water or reduce activity in order to conserve energy.<\/p>\n\n\n\n The results that surprised the researchers<\/strong><\/p>\n\n\n\n But the results presented a completely different picture. During and after the heat waves, the tunas hardly changed their behavior. They continued to swim in the same areas, did not move to greater depths, and did not reduce their activity level. On the surface, this is good news. However, the researchers warn that this may actually be a "hidden vulnerability.". <\/p>\n\n\n\n The fact that the toucans continue to behave as usual does not necessarily indicate that they are not affected by the warming, but rather that they may be paying a heavy physiological price that is not visible to the outside world. The findings are consistent with studies conducted at the University of Hawaii, which tested herbivorous fish species under laboratory conditions simulating marine heat waves. There, too, it was found that the fish did not significantly change their behavior, but physiological tests revealed signs of stress and even a decrease in body mass.<\/p>\n\n\n\n When the danger is not visible<\/strong><\/p>\n\n\n\n The significance of the findings extends far beyond the behavior of the terns themselves. During the study period, a rapid warming event occurred in the Gulf of Eilat, leading to widespread mortality of terns. <\/p>\n\n\n\n The fact that fish do not display behavioral warning signs before being harmed makes it difficult to identify distress in real time, a significant challenge for conservation and environmental management, the researchers said. <\/p>\n\n\n\n If the damage occurs only at the physiological level, the ecosystem may already be under significant stress before this can be observed in animal behavior.<\/p>\n\n\n\n The way to strengthen the reef<\/strong><\/p>\n\n\n\n The researchers emphasize that it is not possible to cool seawater or directly prevent marine heat waves. Therefore, the way to help fish and coral reefs is to reduce other environmental pressures. Preserving marine habitats by preventing pollution, enforcing fishing restrictions, and reducing physical damage to coral reefs can strengthen the resilience of the entire ecosystem. <\/p>\n\n\n\n The healthier the reef, the greater the chance that the toucans and other animals living there will be able to cope with the effects of increasing warming. <\/p>\n\n\n\n The research from the Gulf of Eilat provides a rare glimpse into how climate change is affecting life below the surface. It also reminds us that sometimes the greatest dangers are not those that can be seen with the naked eye, but rather those that occur silently, below the surface.<\/p>\n\n\n\n \""The new research findings are worrying"\"<\/strong><\/p>\n\n\n\n Dr. Assaf Zevuloni, Eilat Bay ecologist at the Israel Nature and Parks Authority: "The findings of the new study are worrying, but they are also essential for understanding our methods of operation. The anemones are the 'gardeners' of the reef, and their function is critical for maintaining the balance between corals and algae. The fact that they do not change their behavior during heat waves, and may actually be hiding severe physiological stress, makes it clear to us that the ecosystem may be close to a tipping point before we even notice it.<\/p>\n\n\n\n \""The current reality presents us with a complex challenge - we have no way to prevent the occurrence of marine heat waves or cool the Gulf waters in the foreseeable future. Therefore, the key tool we have left is to strengthen the local resilience of the reef and its inhabitants. To enable the reefs and other natural values \u200b\u200bto survive the thermal stresses operating on a global scale, we must prevent local stresses that are within our control.". <\/p>\n\n\n\n \""This means ensuring the protection of habitats, the complete prevention of marine pollution, uncompromising awareness and enforcement of fishing restrictions, and the prevention of physical damage to the reef. This is exactly the message of 'Man and the Sea' Month \u2013 strict conservation at the local level is the only chance for the natural system to cope with the upheavals of the global climate crisis."'
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