Post by Andrei Tchentchik on May 1, 2020 11:36:30 GMT 2
(.#A.093).- Climate change: what fate for marine life?
Climate change: what fate for marine life?
PHOTOMONTAGE THE PRESS
Even if the world succeeds in working together to reduce greenhouse gas emissions, climate change will have an inevitable impact on the oceans and coasts. At the most recent annual meeting of the American Association for the Advancement of Science (AAAS) in mid-February in Seattle, a dozen researchers presented their observations and predictions about marine life. A Mathieu Perreault file
Posted on March 8, 2020
The mystery of the oceans
Warmer, more acidic, less oxygenated. This is the general prediction for the impact of climate change on the oceans. But it is very difficult to predict what the effect will be on the complex food chains of marine life.
Acidification
PHOTOMONTAGE THE PRESS
Ocean acidification brought on by climate change is harming organisms with shells. If several zooplankton species have them and are at risk of being affected, it is far from obvious that this will directly translate into a reduction in marine productivity. "Certain types of phytoplankton [microscopic algae] have much more efficient photosynthesis when the CO2 level in the water increases," says Scott Doney, a biologist at the University of Virginia who presented his research to the American Association for the advancement of science (AAAS). "Others can draw energy from the carbon in the water. If there is more, there is more energy. But it is not clear that the small amount of CO2 dissolved in water, which is comparable to the concentration in air, is a big game changer. Even the effect of pH on zooplankton shells is uncertain. "There is an effect on the formation of the shell, but also on the general metabolism of zooplankton," says Doney. Work on the effect of acidification on metabolism is very recent, it is not clear in which direction it will go. "
Oxygen and toxic algae
PHOTOMONTAGE LA PRESSE
Heat stroke and acidification cause waves of coral bleaching.
Ocean acidification may affect some plankton species more than others. "Toxic algae appear to thrive in warm, acidic waters," says Doney. But there, there is also an important effect of the oxygenation of the water. Toxic algae seem to like waters with little oxygen. It is expected that in some areas, especially in the tropics, there will be more stratification of the waters, that the deep waters will mix less with the surface waters and that this will lead to very poorly oxygenated areas. However, little is known about the effect that climate change will have on ocean currents, which could be game-changing in terms of stratification and oxygenation. In this negative portrait for some of the regions highly prized by tourists from rich countries, however, there is good news for the whole world. "The seas most likely to be hit by stratification and low oxygen levels are not the most productive in the world, far from it," said Doney.
The invasions to come
One of the sessions of the AAAS congress in Seattle focused only on parasites and marine viruses. The three researchers, Kristina Miller of Fisheries and Oceans Canada, Carolyn Friedman of the University of Washington, and C. Drew Harvell of Cornell University, said that several diseases devastating to marine animals are more virulent in warm waters. They work on salmon, oysters and starfish, respectively. "It has cascading effects," says Harvell. Sea stars no longer control sea urchin populations, which devastate the algal forests where the juveniles of many species of fish hide. These diseases are also migrating north, where unprotected populations are very vulnerable. In recent years, for example, a parasite affecting the domestic cat (especially dangerous for pregnant women) has reached Alaska, where it causes deaths of marine mammals, notably belugas.
A glimmer of hope
PHOTOMONTAGE THE PRESS
A California oceanologist announced relatively good news at the AAAS convention. James Randerson, of the University of California at Irvine, discovered that water oxygenation models predict a decrease in the tropics, but only until ... 2150. Thereafter, the oxygen-poor areas gradually shrink , until finding the current oxygenation rates. This phenomenon is due to a rebalancing with the Southern Ocean which, moreover, should also decrease the quantity of nitrogen in the tropics from the XXIIth century. Nitrogen levels are increasing in the tropics due to the agricultural boom in emerging countries, as nitrogen from fertilizers is not completely absorbed by the fields.
Robotic sentries
A chemist at the prestigious Woods Hole Oceanographic Institute in Massachusetts believes that underwater drones are the only way to fully understand and predict the changes in marine life that will result from climate change. "We need to understand the basis of marine life, the microbiological processes," said Mak Saito of Woods Hole in Seattle. We have developed an automatic analysis of the main stress biomarkers and microbial enzymes, which will be transported by autonomous underwater drones. This is a project that will diagnose changes at the scale of the oceans. "
Retirement
When we think of climate change and oceans, we usually think of the rising sea level. Harvard University political scientist A.R. Siders presented an action plan to the AAAS conference to deal fairly with evacuations from threatened coastal communities. "My analysis of properties purchased by a national program to evacuate areas that are too often flooded shows that the result is very inequitable," says Siders. In poor neighborhoods, properties will often be bought individually, without an overall plan, at low prices. Those that remain are worth even less, are unsaleable. There is also a problem with tenants, who are often not compensated for their move. It is essential to plan this retreat from our shores to avoid aggravating social inequalities. "
In numbers
6 cm: increase in sea level between 2000 and 2016.
15 cm: increase in sea level between 1880 and 2000 15 to 45 cm: increase in sea level in 2090, compared to now, if the Paris Agreements are respected.
23 to 53 cm: sea level rise in 2090, compared to now, under firm commitments currently made.
Sources: IPCC, Nature
F I N .
Climate change: what fate for marine life?
PHOTOMONTAGE THE PRESS
Even if the world succeeds in working together to reduce greenhouse gas emissions, climate change will have an inevitable impact on the oceans and coasts. At the most recent annual meeting of the American Association for the Advancement of Science (AAAS) in mid-February in Seattle, a dozen researchers presented their observations and predictions about marine life. A Mathieu Perreault file
Posted on March 8, 2020
The mystery of the oceans
Warmer, more acidic, less oxygenated. This is the general prediction for the impact of climate change on the oceans. But it is very difficult to predict what the effect will be on the complex food chains of marine life.
Acidification
PHOTOMONTAGE THE PRESS
Ocean acidification brought on by climate change is harming organisms with shells. If several zooplankton species have them and are at risk of being affected, it is far from obvious that this will directly translate into a reduction in marine productivity. "Certain types of phytoplankton [microscopic algae] have much more efficient photosynthesis when the CO2 level in the water increases," says Scott Doney, a biologist at the University of Virginia who presented his research to the American Association for the advancement of science (AAAS). "Others can draw energy from the carbon in the water. If there is more, there is more energy. But it is not clear that the small amount of CO2 dissolved in water, which is comparable to the concentration in air, is a big game changer. Even the effect of pH on zooplankton shells is uncertain. "There is an effect on the formation of the shell, but also on the general metabolism of zooplankton," says Doney. Work on the effect of acidification on metabolism is very recent, it is not clear in which direction it will go. "
Oxygen and toxic algae
PHOTOMONTAGE LA PRESSE
Heat stroke and acidification cause waves of coral bleaching.
Ocean acidification may affect some plankton species more than others. "Toxic algae appear to thrive in warm, acidic waters," says Doney. But there, there is also an important effect of the oxygenation of the water. Toxic algae seem to like waters with little oxygen. It is expected that in some areas, especially in the tropics, there will be more stratification of the waters, that the deep waters will mix less with the surface waters and that this will lead to very poorly oxygenated areas. However, little is known about the effect that climate change will have on ocean currents, which could be game-changing in terms of stratification and oxygenation. In this negative portrait for some of the regions highly prized by tourists from rich countries, however, there is good news for the whole world. "The seas most likely to be hit by stratification and low oxygen levels are not the most productive in the world, far from it," said Doney.
The invasions to come
One of the sessions of the AAAS congress in Seattle focused only on parasites and marine viruses. The three researchers, Kristina Miller of Fisheries and Oceans Canada, Carolyn Friedman of the University of Washington, and C. Drew Harvell of Cornell University, said that several diseases devastating to marine animals are more virulent in warm waters. They work on salmon, oysters and starfish, respectively. "It has cascading effects," says Harvell. Sea stars no longer control sea urchin populations, which devastate the algal forests where the juveniles of many species of fish hide. These diseases are also migrating north, where unprotected populations are very vulnerable. In recent years, for example, a parasite affecting the domestic cat (especially dangerous for pregnant women) has reached Alaska, where it causes deaths of marine mammals, notably belugas.
A glimmer of hope
PHOTOMONTAGE THE PRESS
A California oceanologist announced relatively good news at the AAAS convention. James Randerson, of the University of California at Irvine, discovered that water oxygenation models predict a decrease in the tropics, but only until ... 2150. Thereafter, the oxygen-poor areas gradually shrink , until finding the current oxygenation rates. This phenomenon is due to a rebalancing with the Southern Ocean which, moreover, should also decrease the quantity of nitrogen in the tropics from the XXIIth century. Nitrogen levels are increasing in the tropics due to the agricultural boom in emerging countries, as nitrogen from fertilizers is not completely absorbed by the fields.
Robotic sentries
A chemist at the prestigious Woods Hole Oceanographic Institute in Massachusetts believes that underwater drones are the only way to fully understand and predict the changes in marine life that will result from climate change. "We need to understand the basis of marine life, the microbiological processes," said Mak Saito of Woods Hole in Seattle. We have developed an automatic analysis of the main stress biomarkers and microbial enzymes, which will be transported by autonomous underwater drones. This is a project that will diagnose changes at the scale of the oceans. "
Retirement
When we think of climate change and oceans, we usually think of the rising sea level. Harvard University political scientist A.R. Siders presented an action plan to the AAAS conference to deal fairly with evacuations from threatened coastal communities. "My analysis of properties purchased by a national program to evacuate areas that are too often flooded shows that the result is very inequitable," says Siders. In poor neighborhoods, properties will often be bought individually, without an overall plan, at low prices. Those that remain are worth even less, are unsaleable. There is also a problem with tenants, who are often not compensated for their move. It is essential to plan this retreat from our shores to avoid aggravating social inequalities. "
In numbers
6 cm: increase in sea level between 2000 and 2016.
15 cm: increase in sea level between 1880 and 2000 15 to 45 cm: increase in sea level in 2090, compared to now, if the Paris Agreements are respected.
23 to 53 cm: sea level rise in 2090, compared to now, under firm commitments currently made.
Sources: IPCC, Nature
F I N .
