The study, published this week in the journal Nature by researchers from Oregon State University and five other institutions, found that on a global scale, a warmer climate could cause a rapid, overall reduction in marine life.
“This clearly showed that overall ocean productivity decreases when the climate warms,” said lead author Michael Behrenfeld, an OSU professor of botany and expert on remote sensing of marine biology.
“There is significant regional variability, with some areas showing enhanced production and some area losses,” Behrenfeld said. “But on a global basis there is an inverse relationship – increased temperatures cause decreased marine phytoplankton production.”
This climate response can be traced to increased stratification in the oceans, the study showed. When the ocean surface warms, it essentially becomes “lighter” than the cold, dense water below, which is loaded with nutrients. This process effectively separates phytoplankton in the surface layer - which need light for photosynthesis - from the nutrients below them, which they also need for growth.
The satellite data used in the study were from NASA’s SeaWiFS satellite, or Sea-viewing Wide-Field-of-view Sensor. Since its launch in 1997, SeaWiFS has measured changes in the color of the ocean - as more and more phytoplankton are added, the color shifts from blue toward green. By studying these color changes from space, scientists can calculate how much phytoplankton pigment is in the water, relate this to photosynthetic rate, and correlate these changes to simultaneous changes in climate.
The first climate-driven change in ocean production measured in this study occurred between 1997 and 1999, when the oceans were recovering from one of the strongest El Nino events on record. With the end of the El Nino, global climate began to cool and there was a surge in ocean phytoplankton productivity that peaked in late 1999.
The second climate event was a long-term warming trend that started in 2000 and continues today. Over this period, the ocean sea surface became overall warmer and more stratified, and phytoplankton productivity went down almost in lockstep at a rate of about 190 million tons of carbon a year. On a regional scale, the decreases in production often exceeded 30 percent.
Despite their microscopic size, ocean phytoplankton are responsible for about half of the photosynthesis on Earth, a process that removes carbon dioxide from the atmosphere and converts it into organic carbon to fuel nearly every ocean ecosystem.
Compared to terrestrial land plants, however, phytoplankton use a very small amount of biomass to convert large amounts of carbon, because they are eaten by predators about as quickly as they grow. The entire global phytoplankton biomass is consumed every two to six days, in contrast to land plants that might have turnover rates of a year to hundreds of years.
“This very fast turnover, along with the fact that phytoplankton are limited to just a thin veneer of the ocean surface where there is enough sunlight to sustain photosynthesis, makes them very responsive to changes in climate,” Behrenfeld said. “This was why we could relate productivity changes to climate variability in only a 10-year record. Such connections would be much harder to detect from space for terrestrial plant biomass.”
Results of the study may provide important insight into how ocean biology might respond to sustained global warming, the researchers said. “A common prediction among global climate models is that warming will cause ocean production to decrease at mid-latitudes and low latitudes, due to intensified stratification,” Behrenfeld said, “This is precisely the response we observed.”
Climate models also predict long term global warming will cause enhanced phytoplankton production near the poles, because of longer growing seasons, and shifts in the organisms dominating different ecosystems across the globe. These predictions have not yet been confirmed by satellite ocean measurements, and detection of them may require a longer record or advances in satellite technology.
Climate not only influences ocean biology, but ocean biology influences climate.
“Rising levels of carbon dioxide in the atmosphere are a key part of global warming,” Behrenfeld said. “This study shows that as the climate warms, phytoplankton production goes down, but this also means that carbon dioxide uptake by ocean plants will decrease. That would allow carbon dioxide to accumulate more rapidly in the atmosphere, making the problem worse.”
Better understanding this “feedback mechanism” which compounds global warming is a top priority for study, the researchers say.
Michael Behrenfeld | EurekAlert!
Safeguarding sustainability through forest certification mapping
27.06.2017 | International Institute for Applied Systems Analysis (IIASA)
Dune ecosystem modelling
26.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
26.07.2017 | Event News
21.07.2017 | Event News
19.07.2017 | Event News
26.07.2017 | Physics and Astronomy
26.07.2017 | Life Sciences
26.07.2017 | Earth Sciences