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Algae invades for the reef

Until now, the common perception was that invasive plants and animals threaten the ecological diversity in the place they invaded. However, a new Israeli study that examined algae that invaded the Mediterranean Sea presents a possibility that the solution to saving the ecosystem lies precisely in them

"Algae are an essential component of marine society, since they form a habitat where dozens and even hundreds of species of small marine creatures live." Photo: Rilov Laboratory
"Algae are an essential component of the marine society, since they form a habitat where dozens and even hundreds of species of small marine creatures live." Photo: Rilov Laboratory

Between the extreme heat loads that are felt these days in Israel, the massive heat wave that recently hit Europe, and the one that is now hitting North America, there is no doubt that the rise in global temperatures as part of the climate crisis is well felt this summer. Beyond its effect on us, humans, the increase in air and sea temperatures in recent decades causes marine creatures that lived in tropical areas to migrate to areas where the temperature was lower in the past. For the most part, the thought is that these creatures, which are defined asInvading species, compete with the local species for food and habitats - until the latter are pushed out and disappear. However, a new Israeli study, presented recently In the 50th Annual Conference on Science and the Environment, reveals that some of them may actually benefit the ecosystem around them.

"In the last 150 years, about 1,000 foreign species of fish, invertebrates and algae have entered the Mediterranean Sea, mainly from the Red Water through the Suez Canal, or from the Atlantic Ocean," says Prof. Gil Rilov, head of the Laboratory for the Ecology of Marine Societies at the National Institute of Oceanography of Seas and Lakes Research for Israel, that the new research was carried out under the guidance and direction of Dr. Jack Silverman Seas and Lakes Research for Israel, led by doctoral student Martina Mols and with the participation of students Tamar Gay-Chaim, Ohad Peleg, Erez Yeruham, and Reut Zamir. Many of these species migrated as part ofThe Leapse migration: The massive migration of fish and other marine creatures from the Red Sea and the Indian Ocean through the Suez Canal to the Mediterranean Sea, which began due to the digging of the canal and continues to this day, and is named after the Suez Canal developer, Ferdinand de Lesseps. This phenomenon has had a significant impact on the ecosystem in the sea, and many of the foreign species probably compete with the local species and harm them. Beyond that, invasive species, in and out of the sea, are a worldwide problem, which is the second most acute cause of the extinction of local species (after habitat loss).

"The global effects of the accelerated warming of the sea and the invasion of species, in addition to the local effects of overfishing and pollution, make Israel a hot spot when it comes to the disappearance of species," says Rilov.

In the geographical area where Israel is located - the Levant basin, the southeastern edge of the Mediterranean - the environmental conditions are naturally extreme, and the area is the hottest in the Mediterranean. This is an area that is heating up especially fast today, andThe constant warming in it leads to the collapse of biological diversity All over the Mediterranean. Studies from previous years on disappearance the molluscs At sea the high school, Andhis disappearance של Hedgehog the sea the purple which was common on our coasts until about 30 years ago, showed the connection between high temperature and the disappearance of local species in the Mediterranean Sea.

An essential component of maritime society

The new study focuses on a comparison between a local algae species called Cystanitis Rice (Gongolaria Rayssiae), and two species of algae that invaded the Mediterranean Sea: Lobophora Schneideri, a relatively recent invader from the Atlantic Ocean, andGalaxaura Rugosa, from the area where the Indian and Pacific oceans meet. In the study, the function of the various algae in the ecosystem was examined, with the aim of understanding whether aliens can replace the local algae that are disappearing in some of their functions.

"Algae are an essential component of marine society, since they form a habitat where dozens and even hundreds of small marine species such as crabs, worms, snails and more live," Rilov explains. "The algae provide a home and food for these creatures and various fish, and their importance as part of the functions of the ecosystem is in the production of oxygen and the absorption of blue carbon (Blue Carbon, carbon dioxide absorbed by marine organisms such as mangrove trees, Seaweeds And of course algae in the process of photosynthesis, the absorption of which reduces the amount of greenhouse gas emitted into the atmosphere, "RA)".

"In the shallow water areas of the Mediterranean Sea, there are many species of Cystanis that are under local and global pressures originating from human activity," says Rilov. "On our shores there are only a few species, and mainly forests, of the local algae, which is endemic to Israel and Lebanon - that is, it cannot be found anywhere else in the Mediterranean Sea. These forests function as an important habitat, but vegetarian fish of a dangerous type that invaded the Mediterranean Sea from the Red Sea in the last century threaten them, due to the aggressive eating of the algae, which turns the rocky reefs of the Mediterranean Sea The 'deserts' are almost bald from bushy algae.'

Algae that can compensate

In the new study, it was discovered that the local algae species is more sensitive to heat - this is in contrast to the invasive species, which are more resistant to high temperatures. Also, the local species is seasonal, and thrives for only a few months a year, between winter and early summer - while the foreign species thrive all year round. "At the beginning of the summer, when the temperature reaches 28-27 degrees, the cistern loses its branches and enters a sort of 'dormancy'," says Rilov. "It is possible that in the past, when the water temperature was lower, the local algae was more productive during a greater number of days a year - but the situation has changed with the existing warming, and will be exacerbated in view of the one that will come in the future."

"Foreign algae have the possibility to compensate for some of the functions of the local algae: both as a habitat, and in the restoration of the loss of blue carbon caused by the impact of global changes and the possible loss of the local species," says Rilov. "Actually, since the local species is seasonal and during the rest of the year its function decreases, in the annual calculation, both foreign species have a higher potential when it comes to absorbing blue carbon than the local species," explains Rilov.

"The foreign algae have the possibility to compensate for some of the functions of the local algae: both as a habitat, and in the restoration of the loss of blue carbon." Photograph by Rilov Laboratory
"Foreign algae have the possibility to compensate for some of the functions of the local algae: both as a habitat, and in restoring the loss of blue carbon." Photograph by Rilov Laboratory

The research findings are also linked to another question: Is the reason why many local species have disappeared from the Mediterranean Sea the invasion of foreign species, the rise in global temperatures - or both? Because the southeast of the Mediterranean Sea is less explored than its western side, andMonitoring Species in our area Apply only At the beginning Century ה-20, it is difficult to prove what was the reason for the disappearance of the various species. "The widespread assumption that the disappearance of species is related to the invasion of other species is problematic, and the issue needs to be investigated and scientific evidence found in order to be able to say this," claims Rilov. According to him, other studies conducted in Israel, including those conducted in the laboratory of Prof. Yonatan Belmakar from Tel Aviv University, reinforce the argument that the warming of the water explains better than competition with foreign species the decrease in the frequency of fish species. "The findings of our research help to strengthen the argument that the increase in sea temperatures is what led to the disappearance of the local species."

"Must train mental flexibility"

As mentioned, the issue of invasive species is far from being limited to the algae examined in the study, and foreign species, such as the haharon fish andHedgehog the sea The black, which are common in the Red Sea, reach the Mediterranean all the time. According to Rilov, the spread of these species in the Mediterranean following the increase in global temperature requires creative and adaptive thinking when it comes to marine nature management and conservation policies. "We need to research every alien species that has a great impact potential, and see what level of impact it has on the functioning of the ecosystem in the context of the climate crisis," he says. "It's always sad to lose a local species, but we must be flexible in our thinking, and use the knowledge gathered with the help of research to make informed decisions about dealing with them - whether it's as threats, or as lifelines in a world and seas that are rapidly warming," he concludes.

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