The smallest and most plentiful creatures of the ocean can’t with the heating of the ocean | Science | EUROtoday

With lower than a thousandth of a millimeter, the Prochlorococcus They are giants. Discovered on the finish of the final century, they’re accountable for a lot of the turquoise colour that tropical seas have. In entrance of terrestrial crops, they’re additionally the primary photosynthetic dwelling beings, metabolizing the sunshine to generate natural carbon, the bottom of marine ecosystems. As a byproduct, 5% of the oxygen accessible for respiratory (its predecessors had been the protagonists of the nice oxidation that stuffed the planet of this ingredient tens of millions of years in the past) launch. However, they don’t carry the warmth effectively and of that, the seas has increasingly. A research revealed in Nature Microbiology He estimates that, by the top of the century, the abundance of those cyanobacteria can be decreased by half. Such descent will trigger cascades results which are nonetheless unknown.

For greater than 10 years, a gaggle of marine oceanographers and biologists has traveled about 150,000 nautical miles (round 277,000 km) in 100 crossings learning phytoplankton (microscopic beings that float on the floor of the ocean). They sought to estimate the abundance of the primary cyanobacteria in keeping with latitude and, particularly, measure the affect of temperature on the cell division and multiplication strategy of Prochlorococcus. You can discover as much as 100,000 cells (they’re unicellular organisms) per cubic millimeter of water. To inform them, they used a bigger model of a tool in any scientific evaluation or hospital laboratory, a move cytometry.

“Having such small agencies requires specialized team,” says François Ribalet, professor of Oceanography on the University of Washington (United States) and first writer of the analysis. “We use a continuous flow cytometer called Seaflow that triggers laser light to the cells as they pass. Each cell of Prochlorococcus It contains chlorophyll that fluoresce when impacted by the laser, creating a unique optical firm that we can detect and count, “adds. Ribalet compares it with an automated microscope that can process tens of thousands of samples per second.” During the last decade, we have analyzed more than 800 billion cells of cells Prochlorococcus In this way! “, Complete.

The results of so much journey confirm that to the Prochlorococcus They like heat. There are not in the poles or in the colder seas. In fact, its abundance increases with latitude, the closer to Ecuador, the more of these cyanobacteria. The maximum of cell division (its replication rhythm) has it in the tropical strip of the Atlantic and in the Indian Ocean, where its populations would be folded, of not mediating the death of the precedents, every 10.5 hours. They also found that the key factor for their multiplication are neither the available nutrients (nitrogen and phosphorus) nor the amount of light, but the thermometer: they found that the cell division ratio increased exponentially as the sea surface temperature approached the 28th, but collapsed from there.

“We have not directly observed population decreases during our 10 -year study, since we show different places every year instead of monitoring fixed sites,” says Ribalet. However, he adds, “when comparing the similar temperature ranges in different years and places, the thermal sensitivity pattern is remarkably consistent: populations are systematically lower in the warmer waters we find.”

Combining their field work with experiments with laboratory crops, they have seen that Prochlorococcus They accelerate their cell division and multiplication from the 19th to a rhythm that becomes exponential by around 28. But when overcoming this threshold, which was a thermal optimal, degenerates in thermal stress: when the water reaches 30º (as has happened this summer on the Spanish Mediterranean coasts), that growth rate is reduced to a third and, beyond, a decrease in populations begins.

“The phytoplankton is the grass of the sea, the ocean forests,” compares the professor of the Oceanographic Center of Gijón (IEO/CSIC), Xosé Anxelu G. Morán. Within it, the main group are Prochlorococcus. “They are so small and each produces so little chlorophyll that went unnoticed by traditional microscopy,” he says. It was not until 1986, when the MIT Sallie Chisholm microbiologist team used flow citometry, that these cyanobacteria became visible. “If they did not exist and the rest of the phytoplankton there would be no primary production, life in the sea depends on the zooplankton being eaten, that the larvae of the fish is eaten the zooplankton, that the small fish eat …” says Morán, which has not intervened in the study.

Because according to the forecasts of the Ribalet team, in the future there will be seas so warm that the Prochlorococcus They will have disappeared from them. With the data accumulated in the last decade, they fed a climate model with two alternative scenarios. One, the most optimistic, foresees for the end of the century an accumulation of carbon dioxide (CO₂) of 650 parts per million (PPM). Today are 424 ppm. The other, the most pessimistic, raises the concentration up to 1,370 ppm, which would imply even more pronounced warming.

Whatever happens with emissions, at best the abundance of Prochlorococcus In tropical seas it will fall by 17%. And in the worst, they could be reduced by 51%. That is the average. “Our models predict that the most severe decreases will occur in the warmest tropical regions, in particular the Western Pacific Warm Pool [la piscina cálida del Pacífico occidental, en inglés] (Around Indonesia, the Philippines and Papua New Guinea), parts of the central Pacific, the warmer areas of the Indian Ocean and the Arabic Sea, ”says Ribalet.

With heat, cell metabolism tends to accelerate. That made scientists think that, with global warming, good times would arrive for cyanobacteria. “The Prochlorococcus It is an ideal machine to make photosynthesis to acquire photo voltaic power and switch it into chemical power, ”recollects Laura Alonso, from the world of ​​Marine Biotechnology and Molecular Ecology of the Azti Research Center. With a really small genome (DNA wants each nitrogen and phosphorus), its mobile equipment calls for little or no,” that’s why it thrives in regions with few nutrients, “provides Alonso. of evolution, marks its limits: “The Prochlorococcus They are not adapted to new temperatures, ”the researcher completes. In crops within the laboratory with a pressure, Alonso and her staff proved how warmth decreased the supply of RNA obligatory to specific gene genes.

Neither the authors of the research nor different consultants within the Prochlorococcus They are clear that they may occur once they start to overlook. His position as an oxygen generator will not be among the many issues, “since one other phytoplankton, akin to Synechococcusthey may compensate for the loss, “says Ribalet. What worries has to do with his role in the trophic chain. Absent these cyanobacteria, the hole would be filled by others, which are much larger. And that detail would have some consequences that summarize, Morán, of the Oceanographic Center of Gijón:“ A small organism, such as the zooplankton, which is eaten to a smaller one [las Prochlorococcus]it cannot be eaten to another bigger [las Synechococcus]”For Alonso, from Azti, what happens is unpredictable:“ Until this study on-sitealmost all have done with isolated crops in the laboratory. Beyond his photosynthetic work, we do not know a lot about his interactions with the rest of the organisms. “