Ocean food web is key in the global carbon cycle
![]() Date:
March 11, 2014 Source: University of California - Santa Barbara Summary: Nothing dies of old age in the ocean. Everything gets eaten and all that remains of anything is waste. But that waste is pure gold to an oceanographer. In a study of the ocean's role in the global carbon cycle, oceanographers used those nuggets to their advantage. They incorporated the lifecycle of phytoplankton and zooplankton -- small, often microscopic animals at the bottom of the food chain -- into a novel mechanistic model for assessing the global ocean carbon export.Nothing dies of old age in the ocean. Everything gets eaten and all that remains of anything is waste. But that waste is pure gold to oceanographer David Siegel, director of the Earth Research Institute at UC Santa Barbara. In a study of the ocean's role in the global carbon cycle, Siegel and his colleagues used those nuggets to their advantage. They incorporated the lifecycle of phytoplankton and zooplankton -- small, often microscopic animals at the bottom of the food chain -- into a novel mechanistic model for assessing the global ocean carbon export. Their findings appear online in the journal Global Biogeochemical Cycles. The researchers used satellite observations including determinations of net primary production (NPP) -- the net production of organic matter from aqueous carbon dioxide (CO2) by phytoplankton -- to drive their food-web-based model. The scientists focused on the ocean's biological pump, which exports organic carbon from the euphotic zone -- the well-lit, upper ocean -- through sinking particulate matter, largely from zooplankton feces and aggregates of algae. Once these leave the euphotic zone, sinking into the ocean depths, the carbon can be sequestered for a season or for centuries. "What we've done here is create the first step toward monitoring the strength and efficiency of the biological pump using satellite observations," said Siegel, who is also a professor of marine science in UCSB's Department of Geography. "The approach is unique in that previous ways have been empirical without considering the dynamics of the ocean food web." The space/time patterns created by those empirical approaches are inconsistent with how oceanographers think the oceans should work, he noted. Carbon is present in the atmosphere and is stored in soils, oceans and Earth's crust. Any movement of carbon between -- or in the case of the ocean, within -- these reservoirs is called a flux. According to the researchers, oceans are a central component in the global carbon cycle through their storage, transport and transformations of carbon constituents. "Quantifying this carbon flux is critical for predicting the atmosphere's response to changing climates," Siegel said. "By analyzing the scattering signals that we got from satellite measurements of the ocean's color, we were able to develop techniques to calculate how much of the biomass occurs in very large or very small particles." Their results predict a mean global carbon export flux of 6 petagrams (Pg) per year. Also known as a gigaton, a petagram is equal to one quadrillion (1015) grams. This is a huge amount, roughly equivalent to the annual global emissions of fossil fuel. At present, fossil fuel combustion represents a flux to the atmosphere of approximately 9 Pg per year. "It matters how big and small the plankton are, and it matters what the energy flows are in the food web," Siegel said. "This is so simple. It's really who eats whom but also having an idea of the biomasses and productivity of each. So we worked out these advanced ways of determining NPP, phytoplankton biomass and the size structure to formulate mass budgets, all derived from satellite data." The researchers are taking their model one step further by planning a major field program designed to better understand the states in which the biological pump operates. "Understanding the biological pump is critical," Siegel concluded. "We need to understand where carbon goes, how much of it goes into the organic matter, how that affects the air-sea exchanges of CO2 and what happens to fossil fuel we have emitted from our tailpipes." Story Source: The above story is based on materials provided by University of California - Santa Barbara. The original article was written by Julie Cohen. Note: Materials may be edited for content and length. |
California and Arizona amaze with two new species of desert poppy
![]() Date: March 11, 2014 Source: Pensoft Publishers Summary: Not quite desert roses, two new species of desert poppies from North America amaze with their simple beauty. The newly described plants are found in the deserts of California and Arizona and have a vibrant yellow colored flowers, typical for all the desert dwellers from the Eschscholzia genus of the poppy family. Who said that there is only sand in the deserts? Not quite desert roses, two new species of desert poppies from North America prove such statements wrong with their simple beauty. The newly described plants are found in the deserts of California and Arizona and have a vibrant yellow colored inflorescences, typical for all the desert dwellers from the Eschscholzia genus of the poppy family. The study was published in the open access journal PhytoKeys. Most commonly known for the iconic California Poppy, the state flower of California, Eschscholzia is a genus in the poppy family Papaveraceae that previously held 12 species. The genus is native to the mainland and islands of western North America in both the United States and Mexico, but the type species, Eschscholzia californica, is commonly spread and has invaded Mediterranean regions around the world. Shannon Still discovered the new species while studyingEschscholzia for his dissertation research at the University of California Davis. "What is interesting about these new species is that, while people have been collecting these plants for decades, they were not recognized as something different" Still said. "They were always confused for existing species. This confusion led to my study of the group, and ultimately, recognizing something new. I imagine there are many more desert plant species that are also understudied." The two new desert species E. androuxii and E. papastillii are found in desert washes, flats, and slopes growing in coarse and sandy soil across California deserts and parts of Arizona. Eschscholzia androuxii has a small range, is fairly uncommon and is suggested that it be listed as a rare plant species. The wide distribution of the other species, suggests there are no conservation threats at the moment. Still acknowledges the resources that lay the foundation for his research. "My work would have been impossible without a strong system of specimen and data sharing from herbaria around the world, and especially in California. I used the herbarium specimens to compare with collections I had made from the field, to establish important characters used to identify the species, and to examine the species' geographic ranges. This work highlights the value that herbarium collections play in cataloging, understanding and conserving our biological diversity." Story Source: The above story is based on materials provided by Pensoft Publishers. The original story is licensed under a Creative Commons License. Note: Materials may be edited for content and length. |
Long-term warming likely to be significant despite recent slowdown
![]() Date:
March 11, 2014 Source: NASA/Goddard Space Flight Center Summary: A new study shows Earth's climate likely will continue to warm during this century on track with previous estimates, despite the recent slowdown in the rate of global warming.new NASA study shows Earth's climate likely will continue to warm during this century on track with previous estimates, despite the recent slowdown in the rate of global warming. This research hinges on a new and more detailed calculation of the sensitivity of Earth's climate to the factors that cause it to change, such as greenhouse gas emissions. Drew Shindell, a climatologist at NASA's Goddard Institute for Space Studies in New York, found Earth is likely to experience roughly 20 percent more warming than estimates that were largely based on surface temperature observations during the past 150 years. Shindell's paper on this research was published March 9 in the journal Nature Climate Change. Global temperatures have increased at a rate of 0.22 Fahrenheit (0.12 Celsius) per decade since 1951. But since 1998, the rate of warming has been only 0.09 F (0.05 C) per decade -- even as atmospheric carbon dioxide continues to rise at a rate similar to previous decades. Carbon dioxide is the most significant greenhouse gas generated by humans. Some recent research, aimed at fine-tuning long-term warming projections by taking this slowdown into account, suggested Earth may be less sensitive to greenhouse gas increases than previously thought. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), which was issued in 2013 and was the consensus report on the state of climate change science, also reduced the lower range of Earth's potential for global warming. To put a number to climate change, researchers calculate what is called Earth's "transient climate response." This calculation determines how much global temperatures will change as atmospheric carbon dioxide continues to increase -- at about 1 percent per year -- until the total amount of atmospheric carbon dioxide has doubled. The estimates for transient climate response range from near 2.52 F (1.4 C) offered by recent research, to the IPCC's estimate of 1.8 F (1.0 C). Shindell's study estimates a transient climate response of 3.06 F (1.7 C), and determined it is unlikely values will be below 2.34 F (1.3 C). Shindell's paper further focuses on improving our understanding of how airborne particles, called aerosols, drive climate change in the Northern Hemisphere. Aerosols are produced by both natural sources -- such as volcanoes, wildfire and sea spray -- and sources such as manufacturing activities, automobiles and energy production. Depending on their make-up, some aerosols cause warming, while others create a cooling effect. In order to understand the role played by carbon dioxide emissions in global warming, it is necessary to account for the effects of atmospheric aerosols. While multiple studies have shown the Northern Hemisphere plays a stronger role than the Southern Hemisphere in transient climate change, this had not been included in calculations of the effect of atmospheric aerosols on climate sensitivity. Prior to Shindell's work, such calculations had assumed aerosol impacts were uniform around the globe. This difference means previous studies have underestimated the cooling effect of aerosols. When corrected, the range of likely warming based on surface temperature observations is in line with earlier estimates, despite the recent slowdown. One reason for the disproportionate influence of the Northern Hemisphere, particularly as it pertains to the impact of aerosols, is that most human-made aerosols are released from the more industrialized regions north of the equator. Also, the vast majority of Earth's landmasses are in the Northern Hemisphere. This furthers the effect of the Northern Hemisphere because land, snow and ice adjust to atmospheric changes more quickly than the oceans of the world. "Working on the IPCC, there was a lot of discussion of climate sensitivity since it's so important for our future," said Shindell, who was lead author of the IPCC Fifth Assessment Report's chapter on Anthropogenic and Natural Radiative Forcing. "The conclusion was that the lower end of the expected warming range was smaller than we thought before. That was a big discussion. Yet, I kept thinking, we know the Northern Hemisphere has a disproportionate effect, and some pollutants are unevenly distributed. But we don't take that into account. I wanted to quantify how much the location mattered." Shindell's climate sensitivity calculation suggests countries around the world need to reduce greenhouse gas emissions at the higher end of proposed emissions reduction ranges to avoid the most damaging consequences of climate change. "I wish it weren't so," said Shindell, "but forewarned is forearmed." Story Source: The above story is based on materials provided by NASA/Goddard Space Flight Center. Note: Materials may be edited for content and length. |
Exotic plant species alter ecosystem productivity
![]() Date: March 11, 2014 Source: Helmholtz Centre For Environmental Research - UFZ Summary: Biologists have reported an increase in biomass production in ecosystems colonized by non-native plant species. In the face of climate change, these and other changes to ecosystems are predicted to become more frequent, according to the researchers.In their joint publication in the journal Ecology Letters German and American biologists have reported an increase in biomass production in ecosystems colonised by non-native plant species. In the face of climate change, these and other changes to ecosystems are predicted to become more frequent, according to the researchers. All over the world, plant and animal species are increasingly encroaching upon ecosystems where they don't belong as a result of human influence. This phenomenon is known as a biological invasion. Observational studies on biological invasions show that the invasion of non-native plant species can alter ecosystems. One important aspect of this is biomass production: compared to intact ecosystems, the productivity of ecosystems with non-native species is considerably higher. "In such purely observational studies however, it is not possible to differentiate between cause and effect," says Dr. Harald Auge from the Helmholtz Center for Environmental Research (UFZ). "The question is whether exotic plant species prefer to colonise more productive ecosystems, or whether increased productivity is a result of the invasion." To get to the bottom of this question, UFZ researchers joined forces with colleagues from the Martin-Luther University Halle-Wittenberg, the University of Montana, the University of California and the US Forest Service and staged invasions by setting up experimental sites in three disparate grassland regions -in Central Germany, Montana and California, on which 20 native plant species (from the respective region) and 20 exotic plant species were sown. Researchers investigated whether and to which extent herbivorous small mammals such as mice, voles or ground squirrels as well as mechanical disturbance to the soil would influence exotic plant species colonizing ability. "The experimental design was exactly the same for all three regions to ensure comparability. We wanted to find out whether superordinate relationships were playing a role, irrespective of land use, species compositions and climate differences," explains Dr Auge. When the experimental sites were not subject to any mechanical disturbance and when herbivorous small mammals had open access to the sites, then no differences could be found between the three regions in their reaction to the sowing of exotic species: biomass production was found to be only slightly higher than for ecosystems with exclusively native plant species, and susceptibility to invasions was low. "The herbivorous small mammals really surprised us," says Dr Auge. "Their presence and appetite is largely responsible for the resistance of grasslands to exotic plant species invasions." If the herbivorous small mammals were excluded using fences or the soil disturbed mechanically or both, then the results were considerably different: ecosystems proved to be less resistant to invasions and biomass production turned out to be considerably higher. "It was perplexing that an increase in productivity applied to all three (from a climate perspective) completely disparate regions. Hence, there seems to be a universal phenomenon going on: exotic plant species do not necessarily prefer more productive ecosystems -their exotic provenance as such leads to an increased production of biomass, which is thus an effect and not the cause of the invasion," Dr Auge resumes. So far there has been no explanation as to why exotic plant species increase biomass production so dramatically. It is possible that only those non-native species that are particularly productive and competitive are able to establish successfully in a new area. Another cause could be the lack of parasites and pathogens specialised on these species. To investigate the long-term reactions of grassland ecosystems on the establishment of non-native plant species, the researchers plan future investigations on the further development of the species on the experimental sites. Dr Auge: "We assume that the non-natives will increasingly crowd out the natives from the ecosystem -a reduction in species richness would imply another dramatic change to native ecosystems." Story Source: The above story is based on materials provided by Helmholtz Centre For Environmental Research - UFZ. Note: Materials may be edited for content and length. |