Toxic Ocean Conditions During Major Extinction 93.9 Million Years Ago Quantified: Doesn’t Take Much Sulfide to Impact Ocean Life
Oxygen in the atmosphere and ocean rose dramatically about 600 million years ago, coinciding with the first proliferation of animal life. Since then, numerous short lived biotic events — typically marked by significant climatic perturbations — took place when oxygen concentrations in the ocean dipped episodically.
The most studied and extensive of these events occurred 93.9 million years ago. By looking at the chemistry of rocks deposited during that time period, specifically coupled carbon and sulfur isotope data, a research team led by University of California, Riverside biogeochemists reports that oxygen-free and hydrogen sulfide-rich waters extended across roughly five percent of the global ocean during this major climatic perturbation — far more than the modern ocean’s 0.1 percent but much less than previous estimates for this event.
The research suggests that previous estimates of oxygen-free and hydrogen sulfide-rich conditions, or “euxinia,” were too high. Nevertheless, the limited and localized euxinia were still sufficiently widespread to have dramatic effect on the entire ocean’s chemistry and thus biological activity.
“These conditions must have impacted nutrient availability in the ocean and ultimately the spatial and temporal distribution of marine life,” said team member Jeremy D. Owens, a former UC Riverside graduate student, who is now a postdoctoral scientist at the Woods Hole Oceanographic Institution. “Under low-oxygen environments, many biologically important metals and other nutrients are removed from seawater and deposited in the sediments on the seafloor, making them less available for life to flourish.”
“What makes this discovery particularly noteworthy is that we mapped out a landscape of bioessential elements in the ocean that was far more perturbed than we expected, and the impacts on life were big,” said Timothy W. Lyons, a professor of biogeochemistry at UCR, Owens’s former advisor and the principal investigator on the research project.
Study results appear online this week in the Proceedings of the National Academy of Sciences.
Across the event 93.9 million years ago, a major biological extinction in the marine realm has already been documented. Also associated with this event are high levels of carbon dioxide in the atmosphere, which are linked to elevated ocean and atmospheric temperatures. Associated consequences include likely enhanced global rainfall and weathering of the continents, which further shifted the chemistry of the ocean.
“Our work shows that even though only a small portion of the ocean contained toxic and metal-scavenging hydrogen sulfide, it was sufficiently large so that changes to the ocean’s chemistry and biology were likely profound,” Owens said. “What this says is that only portions of the ocean need to contain sulfide to greatly impact biota.”
For their analysis, the researchers collected seafloor mud samples, now rock, from multiple localities in England and Italy. They then performed chemical extraction on the samples to analyze the sulfur isotope compositions in order to estimate the chemistry of the global ocean.
According to the researchers, the importance of their study is elevated by the large amount of previous work on the same interval and thus the extensive availability of supporting data and samples. Yet despite all this past research, the team was able to make a fundamental discovery about the global conditions in the ancient ocean and their impacts on life.
“Today, we are facing rising carbon dioxide contents in the atmosphere through human activities, and the amount of oxygen in the ocean may drop correspondingly in the face of rising seawater temperatures,” Lyons said. “Oxygen is less soluble in warmer water, and there are already suggestions of such decreases. In the face of these concerns, our findings from the warm, oxygen-poor ancient ocean may be a warning shot about yet another possible perturbation to marine ecology in the future.”
A species of humpback dolphin previously unknown to science is swimming in the waters off northern Australia, according to a team of researchers working for the Wildlife Conservation Society, the American Museum of Natural History, and numerous other groups that contributed to the study.
To determine the number of distinct species in the family of humpback dolphins (animals named for a peculiar hump just below the dorsal fin), the research team examined the evolutionary history of this family of marine mammals using both physical features and genetic data. While the Atlantic humpback dolphin is a recognized species, this work provides the best evidence to date to split the Indo-Pacific humpback dolphin into three species, one of which is completely new to science.
“Based on the findings of our combined morphological and genetic analyses, we can suggest that the humpback dolphin genus includes at least four member species,” said Dr. Martin Mendez, Assistant Director of WCS’s Latin America and the Caribbean Program and lead author of the study. “This discovery helps our understanding of the evolutionary history of this group and informs conservation policies to help safeguard each of the species.”
The authors propose recognition of at least four species in the humpback dolphin family: the Atlantic humpback dolphin (Sousa teuszii), which occurs in the eastern Atlantic off West Africa; the Indo-Pacific humpback dolphin (Sousa plumbea), which ranges from the central to the western Indian Ocean; another species of Indo-Pacific humpback dolphin (Sousa chinensis), which inhabits the eastern Indian and western Pacific Oceans; and a fourth Sousa species found off northern Australia yet to be named (the formal adjustment of the naming and number of species occurs through a separate and complementary process based on these findings).
“New information about distinct species across the entire range of humpback dolphins will increase the number of recognized species, and provides the needed scientific evidence for management decisions aimed at protecting their unique genetic diversity and associated important habitats,” said Dr. Howard Rosenbaum, Director of WCS’s Ocean Giants Program and senior author on the paper.
Working to bring taxonomic clarity to a widespread yet poorly known group of dolphins, the authors assembled a large collection of physical data gathered mostly from beached dolphins and museum specimens. Specifically, the team examined features from 180 skulls covering most of the distribution area of the group in order to compare morphological characters across this region.
The researchers also collected 235 tissue samples from animals in the same areas, stretching from the eastern Atlantic to the western Pacific Oceans, analyzing both mitochondrial and nuclear DNA for significant variations between populations.
The humpback dolphin grows up to 8 feet in length and ranges from dark gray to pink and/or white in color. The species generally inhabits coastal waters, deltas, estuaries, and occurs throughout the Indian and Pacific oceans to the coasts of Australia. The Atlantic humpback dolphin is considered “Vulnerable” according to the IUCN Red List, whereas the Indo-Pacific dolphin species Sousa chinensis is listed as “Near Threatened.” Humpback dolphins are threatened by habitat loss and fishing activity.
Reference: Martin Mendez, Thomas J. Jefferson, Sergios-Orestis Kolokotronis, Michael Krützen, Guido J. Parra, Tim Collins, Giana Minton, Robert Baldwin, Per Berggren, Anna Särnblad, Omar A. Amir, Vic M. Peddemors, Leszek Karczmarski, Almeida Guissamulo, Brian Smith, Dipani Sutaria, George Amato, Howard C. Rosenbaum. Integrating multiple lines of evidence to better understand the evolutionary divergence of humpback dolphins along their entire distribution range: a new dolphin species in Australian waters? Molecular Ecology, 2013; DOI: 10.1111/mec.12535
Researchers from Nanjing Normal University and BGI report their original genomic research on Baiji, also known as Yangtze River dolphin (Lipotes vexillifer). The study gives new insight into the genetic and evolutionary adaptations of Dolphin, and provides valuable resources for the conservation of mammals and cetaceans in particular. The latest study was published online in the journal Nature Communications.
Nicknamed “Goddess of the Yangtze,” the baiji was regarded as the goddess of protection by local fishermen and boatmen in China. Unfortunately, this species has suffered huge losses in recent decades largely due to the extreme pressures brought by human’s activities. The baiji has become one of the most famous species in aquatic conservation. There have been many great efforts made to conserve the baiji, but most of them failed.
In this study, researchers presented a high-quality draft genome and three re-sequenced genomes of the baiji using next-gen sequencing technology. Comparative genomic analysis revealed that cetaceans (baiji and the bottlenose dolphin) have a slower molecular clock than previous thought.
The further analysis reveals that the genes involved in oxidoreductase activity, ferric iron binding, metabolic processes and ATPase activity show significant expansion, whereas the genes involved in olfactory receptor activity decreased most significantly. Researchers suggested that these changes of genes maybe related with the baiqi’s basic physiological activities required for underwater living, such as oxygen carrying and sensing.
Researchers found there were many factors related with the aquatic adaptations of cetaceans, such as positively selected genes (PSGs), and some functional changes. One of the noticeable findings is that PSGs in the baiji lineage were also involved in DNA repair and response to DNA damage stimulus, which have not been reported in previous studies of mammals or dolphin.
The independent origin of echolocation in toothed whales and echolocating bats is a classic model of convergent evolution. When identifying genes exhibiting convergent evolution in the baiji and bat, researchers found nine genes (including SLC26A5, TMC1, and DFNB59) have evolved under significant accelerated evolution, and 17 genes contained parallel amino acid changes in echolocating mammals.
Compared to all other mammalian genomes reported so far, researchers also found a significantly lower number of heterozygous single nucleotide polymorphisms (SNPs) in the baiji. The reconstruction of the demographic history of the baiji indicated that a bottleneck occurred near the end of the last deglaciation, a time coinciding with a rapid decrease in temperature and the rise of eustatic sea level.
Fengming Sun, project manager from BGI, said, “We not only found some special evolutionary characterics of baiji, but also found that the functionally extinct of this species was mainly due to human activities. The high-quality draft genome of baiji will provide a valuable resource for researchers to uncover the genetic mechanisms underlying extinct species, and will make a great contribution to the protection of endangered species.”
Reference: Xuming Zhou, Fengming Sun, Shixia Xu, Guangyi Fan, Kangli Zhu, Xin Liu, Yuan Chen, Chengcheng Shi, Yunxia Yang, Zhiyong Huang, Jing Chen, Haolong Hou, Xuejiang Guo, Wenbin Chen, Yuefeng Chen, Xiaohong Wang, Tian Lv, Dan Yang, Jiajian Zhou, Bangqing Huang, Zhengfei Wang, Wei Zhao, Ran Tian, Zhiqiang Xiong, Junxiao Xu, Xinming Liang, Bingyao Chen, Weiqing Liu, Junyi Wang, Shengkai Pan, Xiaodong Fang, Ming Li, Fuwen Wei, Xun Xu, Kaiya Zhou, Jun Wang, Guang Yang. Baiji genomes reveal low genetic variability and new insights into secondary aquatic adaptations. Nature Communications, 2013; 4 DOI: 10.1038/ncomms3708
A new study offers an explanation for the extraordinary run of wet summers experienced by Britain and northwest Europe between 2007 and 2012. The study found that loss of Arctic sea ice shifts the jet stream further south than normal resulting in increased rain during the summer in northwest Europe.
Dr James Screen from the University of Exeter used a computer model to investigate how the dramatic retreat of Arctic sea ice influences the European summer climate. He found that the pattern of rainfall predicted by the model closely resembles the rainfall pattern of recent summers. The study is published in the journal Environmental Research Letters.
Dr Screen said: “The results of the computer model suggest that melting Arctic sea ice causes a change in the position of the jet stream and this could help to explain the recent wet summers we have seen.
“The study suggests that loss of sea ice not only has an effect on the environment and wildlife of the Arctic region but has far reaching consequences for people living in Europe and beyond.”
Jet streams are currents of strong winds high in the atmosphere — around the height at which aeroplanes fly. These winds steer weather systems and their rain. Normally in summer the jet stream lies between Scotland and Iceland and weather systems pass north of Britain. When the jet stream shifts south in summer, it brings unseasonable wet weather to Britain and northwest Europe causing havoc for tourism and farming.
The model suggests that while summer rainfall increases in northwest Europe, Mediterranean regions will receive less rain. The effects are not limited to Europe — weather systems as far as North America could also be influenced.
The annual average extent of Arctic sea ice is currently declining at about half a million square kilometres per decade — equivalent to about twice the area of the UK. The study compared weather patterns during low sea ice conditions as seen in recent years to weather patterns during high sea ice conditions typical of the late 1970s. The model did not use estimates of how much sea ice there will be in the future, and so this study cannot predict future weather. The results do suggest however that if sea ice loss continues as it has over recent decades, the risk of wet summers may increase.
Other studies have suggested that recent ocean warming of the North Atlantic could also be responsible for more summer rain in northwest Europe. It is likely that several other factors, combined with the impact of melting Arctic sea ice, explain the recent run of wet summers.
The next step is to use estimates of future sea ice loss to make predictions of how further melting could influence summer rainfall in Europe in the years to come.
Reference: J A Screen. Influence of Arctic sea ice on European summer precipitation. Environmental Research Letters, 2013; 8 (4): 044015 DOI: 10.1088/1748-9326/8/4/044015
Coral reefs may be able to adapt to moderate climate warming, improving their chance of surviving through the end of this century, if there are large reductions in carbon dioxide emissions, according to a study funded by NOAA and conducted by the agency’s scientists and its academic partners. Results further suggest corals have already adapted to part of the warming that has occurred.
“Earlier modeling work suggested that coral reefs would be gone by the middle of this century. Our study shows that if corals can adapt to warming that has occurred over the past 40 to 60 years, some coral reefs may persist through the end of this century,” said study lead author Cheryl Logan, Ph.D., an assistant professor in California State University Monterey Bay’s Division of Science and Environmental Policy. The scientists from the university, and from the University of British Columbia, were NOAA’s partners in the study.
Warm water can contribute to a potentially fatal process known as coral “bleaching,” in which reef-building corals eject algae living inside their tissues. Corals bleach when oceans warm only 1-2°C (2-4°F) above normal summertime temperatures. Because those algae supply the coral with most of its food, prolonged bleaching and associated disease often kills corals.
The study, published online in the journal Global Change Biology, explores a range of possible coral adaptive responses to thermal stress previously identified by the scientific community. It suggests that coral reefs may be more resilient than previously thought due to past studies that did not consider effects of possible adaptation.
The study projected that, through genetic adaptation, the reefs could reduce the currently projected rate of temperature-induced bleaching by 20 to 80 percent of levels expected by the year 2100, if there are large reductions in carbon dioxide emissions.
“The hope this work brings is only achieved if there is significant reduction of human-related emissions of heat-trapping gases,” said Mark Eakin, Ph.D., who serves as director of the NOAA Coral Reef Watch monitoring program, which tracks bleaching events worldwide. “Adaptation provides no significant slowing in the loss of coral reefs if we continue to increase our rate of fossil fuel use.”
“Not all species will be able to adapt fast enough or to the same extent, so coral communities will look and function differently than they do today,” CalState’s Logan said.
While this paper focuses on ocean warming, many other general threats to coral species have been documented to exist that affect their long-term survival, such as coral disease, acidification, and sedimentation. Other threats to corals are sea-level rise, pollution, storm damage, destructive fishing practices, and direct harvest for ornamental trade.
According to the Status of Coral Reefs of the World: 2000 report, coral reefs have been lost around the world in recent decades with almost 20 percent of reefs lost globally to high temperatures during the 1998-1999 El Niño and La Niña and an 80 percent percent loss of coral cover in the Caribbean was documented in a 2003 Science paper. Both rates of decline have subsequently been documented in numerous other studies as an on-going trend.
Tropical coral reef ecosystems are among the most diverse ecosystems in the world, and provide economic and social stability to many nations in the form of food security, where reef fish provide both food and fishing jobs, and economic revenue from tourism. Mass coral bleaching and reef death has increased around the world over the past three decades, raising questions about the future of coral reef ecosystems.
In the study, researchers used global sea surface temperature output from the NOAA/GFDL Earth System Model-2 for the pre-industrial period though 2100 to project rates of coral bleaching.
Because initial results showed that past temperature increases should have bleached reefs more often than has actually occurred, researchers looked into ways that corals may be able to adapt to warming and delay the bleaching process.
The article calls for further research to test the rate and limit of different adaptive responses for coral species across latitudes and ocean basins to determine if, and how much, corals can actually respond to increasing thermal stress.
Reference: Cheryl A. Logan, John P. Dunne, C. Mark Eakin, Simon D. Donner. Incorporating adaptive responses into future projections of coral bleaching. Global Change Biology, 2013; DOI: 10.1111/gcb.12390
Light enhances brain activity during a cognitive task even in some people who are totally blind, according to a study conducted by researchers at the University of Montreal and Boston’s Brigham and Women’s Hospital. The findings contribute to scientists’ understanding of everyone’s brains, as they also revealed how quickly light impacts on cognition. “We were stunned to discover that the brain still respond significantly to light in these rare three completely blind patients despite having absolutely no conscious vision at all,” said senior co-author Steven Lockley.
“Light doesn’t just allow us to see, it tells the brain whether it’s night or day which in-turn ensures that our physiology, metabolism and behavior are synchronized with environmental time.” “For diurnal species like ours, light stimulates day-like brain activity, improving alertness and mood, and enhancing performance on many cognitive tasks,” explained senior co-author Julie Carrier. The results indicate that their brains can still “see,” or detect, light via a novel photoreceptor in the ganglion cell layer of the retina, different from the rods and cones we use to see.
Scientists believe, however, that these specialized photoreceptors in the retina also contribute to visual function in the brain even when cells in the retina responsible for normal image formation have lost their ability to receive or process light. A previous study in a single blind patient suggested that this was possible but the research team wanted to confirm this result in different patients. To test this hypothesis, the three participants were asked to say whether a blue light was on or off, even though they could not see the light. “We found that the participants did indeed have a non-conscious awareness of the light — they were able to determine correctly when the light was on greater than chance without being able to see it,” explained first author Gilles Vandewalle.
The next steps involved looking closely at what happened to brain activation when light was flashed at their eyes at the same time as their attentiveness to a sound was monitored. “The objective of this second test was to determine whether the light affected the brain patterns associated with attentiveness — and it did,” said first author Olivier Collignon.
Finally, the participants underwent a functional MRI brain scan as they performed a simple sound matching task while lights were flashed in their eyes. “The fMRI further showed that during an auditory working memory task, less than a minute of blue light activated brain regions important to perform the task. These regions are involved in alertness and cognition regulation as well being as key areas of the default mode network,” Vandewalle explained. Researchers believe that the default network is linked to keeping a minimal amount of resources available for monitoring the environment when we are not actively doing something. “If our understanding of the default network is correct, our results raise the intriguing possibility that light is key to maintaining sustained attention” agreed Lockley and Carrier. “This theory may explain why the brain’s performance is improved when light is present during tasks.”
Reference: Gilles Vandewalle, Olivier Collignon, Joseph T. Hull, Véronique Daneault, Geneviève Albouy, Franco Lepore, Christophe Phillips, Julien Doyon, Charles A. Czeisler, Marie Dumont, Steven W. Lockley, Julie Carrier. Blue Light Stimulates Cognitive Brain Activity in Visually Blind Individuals. Journal of Cognitive Neuroscience, 2013; : 2072 DOI: 10.1162/jocn_a_00450
It’s a view as good as gold. A loop high above Saturn by NASA’s Cassini spacecraft revealed this stately view of the golden-hued planet and its main rings. The observation and resulting image mosaic were planned as one of three images for Cassini’s 2013 Scientist for a Day essay contest. The contest challenges students to study three possible targets and write about which one they think will yield the best science. Today is the last day for U.S. submissions and the Cassini mission has already started working on picking the best essays.
This natural-color view — seen as human eyes would have seen it – was obtained on Oct. 10, 2013. It shows off the differently colored bands of weather at Saturn. A bright, wavy stream of clouds around 42 degrees north latitude appears to mark some of the turbulent aftermath of a giant storm that reached its violent peak in early 2011. The mysterious six-sided weather pattern known as the hexagon is also visible around Saturn’s north pole.
When Cassini arrived in 2004, more of the northern hemisphere sported a bluish hue and it was northern winter. The golden tones dominated the southern hemisphere, where it was southern summer. But as the seasons have turned and northern summer has begun, the colors have begun to change in each hemisphere as well. Golden tones have started to dominate in the northern hemisphere and the bluish color in the north is now confined to a tighter circle around the north pole.
Cassini is currently in a special set of tilted orbits known as “inclined orbits” that allow the spacecraft to swing up over the north pole and below the south pole. Cassini was tilted as much as 62 degrees from the plane of Saturn’s equator in April of this year and will continue to work its way back down again till early 2015. Much of Cassini’s tour has involved orbits around the equatorial plane, where most of Saturn’s rings and moons are located.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team consists of scientists from the United States, the United Kingdom, France and Germany. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.