Tag Archives: ocean

Meet Loki – one of our oldest, primeval ancestors

The Arctic might seem like a desolate place, but in fact new research suggests a lot of vibrant activity beneath its rapidly diminishing sheets of ice, with a rather surprising find hidden rather deep within the hydrothermal vents at the floor of the Arctic Ocean, where scientists discovered a new and unusual organism which may finally bring to light a significant evolutionary link from the days when life on Earth was simple, comprised of a single cell to when cells became multiple and further complex life forms first took shape.

The recently discovered microbe along with its relatives belonged to the group Lokiarchaeota, named for the trickster god from Norse mythology. They were described in depth in the latest issue of the journal Nature – single-celled organisms who display a rather unusual mix of traits more commonly found among eukaryotes — the taxon that consists of all complex cellular life forms on Earth – including all species of animals, plants and fungi. Even the single-celled protozoan such as amoebas are eukaryotes.

Evolutionary biologists have estimated that the earliest line of the eukaryotes first evolved some two billion years ago, in what was perhaps the most significant transition in the history of life on this planet – the moment at which it was determined beings like us would one day exist. However, until now there has been very little evidence of when these events began to take place, with few fossilized remains to help them map out the gradual process along the way, and a lack of transitional forms from prokaryotic to eukaryotic.

On Wednesday, a team of scientists changed all this when they proudly announced the discovery of such a transitional form. In the far depths of the Arctic Ocean, where just enough heat circulates to encourage life, the scientists discovered microbes which contain many — but not all — of those features which had previously only been singular in eukaryotes. These microbes could provide us with an indication of what the precursors of complex cellular organisms actually looked like.

“This is a genuine breakthrough,” said Eugene Koonin, an evolutionary biologist at the National Center for Biotechnology Information who did not partake in the research. “It’s almost too good to be true.”

Back in the 1970s, scientists picked up the first major piece of evidence about how life evolved from a single cell to many. Carl Woese, a microbiologist from the University of Illinois, along with his colleagues looked at the genetic material across different species in order to reconstruct the tree of life, an effort that would later become the scientific practice of phylogenetics. This analysis broke life forms down into three major branches.

The first branch included bacteria, with such familiar species as E. coli, located in the intestines of living animals. A second branch was described by Dr. Woese as archaea, consisting of the lesser-known species of microbes, extremophiles, which thrive in high stress environments such as bogs or hot springs. Eukaryotes, which comprise the third branch, have much more in common with archaea than they do with bacteria, and are more closely related to the former.

Over the last four decades, during which scientists identified new species of microbes and created powerful new ways for comparing their DNA, Woese’s tree of life has become clearer. Many of the most recent studies now indicate that eukaryotes are in fact not a third individual branch. Rather, they evolved from the archaea.

Thijs J. G. Ettema, a microbiologist at Upssala University in Sweden, was particularly enamored by the fact that many species of archaea closely related to eukaryotes grew colonies on the deep sea floor. It remains likely that in the near future, scientists could discover even closer relatives between the two, hiding near the hydrothermal vents.

It was discovered quite by accident, when Steffen L. Jorgensen, a microbiologist from the University of Bergen, was digging up samples of sediment at a full two miles beneath the surface of the Arctic Ocean. An initial glimpse of this sediment revealed several types of archaea living among the layers. Dr. Jorgensen then offered some of his samples to Dr. Ettema so he could take a closer look.

Dr. Ettema and his colleagues took it a step further, attempting to extract DNA out of the sediment for further analysis, which is quite a risky undertaking.

Dr. Jorgensen was only able to provide a teaspoon size amount of the sediment, one that Dr. Ettema was sure couldn’t contain too many microbes.

As the environment they are used to is cold and dark, the microbes barely grow. If you offered a spoonful soil out of your own backyard, it would likely contain a million times the amount of microbes.

It soon became clear that Dr. Ettema and his colleagues would have to spend just about every bit of the sediment just to get enough DNA for an accurate analysis. Any accidents that might happen along the way would leave them nothing to study.

“There was just one shot,” Dr. Ettema recalled.

Luckily, Dr. Ettema and his colleagues were successful in their experiment. It so happened that this particular sample of the sediment held DNA carried from a lineage of archaea that was unlike any kind ever discovered before. The scientists decided to call it Lokiarchaeum, for the hydrothermal vent near where it was found, which is known as Loki’s Castle.

Analyzing the DNA, the researchers found that Lokiarchaeum is far more closely related to eukaryotes than any other known species of archaea. But even more surprising was that it had genes for many traits that had only been found previously in eukaryotes.

Among the bundles of genes they discovered were ones that coded for special compartments within eukaryote cells. These compartments, which are known as lysosomes, allow the eukaryote cells to eliminate any defective proteins.

All eukaryotes also possess a cellular skeleton which is constantly being rebuilt and torn apart as their shape changes. Dr. Ettema, along with his colleagues found that many of the genes in Lokiarchaeum code for the same type of proteins necessary for building such a skeleton.

It could be likely that the Lokiarchaeum use their skeletons for crawling over surfaces in the same way that protozoans do. Lokiarchaeum’s genes also indicate that they may be able to swallow up molecules or smaller microbes just as eukaryotes do.

At the present time, Lokiarchaeum appears to be far more complex than other archaea and bacteria, although not as complex as true eukaryotes. The new study indicates that they lacked a nucleus and mitochondria.

But Dr. Ettema’s discovery sheds light on how a creature resembling the Lokiarchaeum may have subsequently evolved into the first full-blown eukaryotes.

After the ancestors of eukaryotes had developed a complex skeleton, the second major step could have been the beginning of mitochondria, which provides energy to the cell.

Scientists have long known that mitochondria evolved from bacteria. They carry their own DNA, which more closely resembles the genetic strands found in free-living bacteria than the genes within the cell’s nucleus.

A number of the researchers propose that the common ancestors of all eukaryotes consumed some free-living bacteria. The bacteria became mitochondria, providing fuel for their host cell.

Lokiarchaeum, which holds the potential to graze for microbes, may be exactly the type of microbe needed for this scenario.

Once the early eukaryotes developed mitochondria, they acquired the energy needed for fueling a much larger and more complex cell. In 2006, Drs. Koonin and William Martin at the University of Düsseldorf suggested that the development of mitochondria encouraged the gradual evolution of the cell’s powerhouse – a nucleus.

The two different sets of genes could cause a whole host of damage, were they to interfere with each other. Drs. Koonin and Martin suggested that eukaryotes gradually build a barrier to keep them separated.

As much as the Lokiarchaeum’s genes may reveal, there are limits on how many clues they can give the scientists. “We don’t even know how big the cells are,” said Dr. Ettema.

Dr. Ettema and his colleagues are now focusing on the Lokiarchaeum microbes. They’ve acquired some new sediment samples, and they are now able to determine how many microbes are inside them. Unfortunately, due to the pressure and harsh lighting of a laboratory setting, the microbes often die out before the scientists are able to find out much about them.

So the researchers have another task lying ahead: how to best recreate the conditions suitable for the growth and survival of these microbes will replicating the extreme temperatures and high pressure that the Lokiarchaeum have grown accustomed to. Before they can do that, however, they still need to determine some other factors necessary for the survival of the microbes, such as the type of carbon necessary for their survival.

“It’s definitely not easy,” said Dr. Ettema, “but we’re not giving up. There are so many questions — this is a whole new biology we have to study.”

James Sullivan
James Sullivan is the assistant editor of Brain World Magazine and a contributor to Truth Is Cool and OMNI Reboot. He can usually be found on TVTropes or RationalWiki when not exploiting life and science stories for another blog article.

Atlantic Ocean Current Growing Weaker Over Last Millennia

The Atlantic has had an uneasy last few centuries – from a 990 mile patch of garbage found in its northern portion (about the distance from Cuba to Virginia), and growing by eight tons of plastic each year, to the heavy absorption of man-cause CO2 cooking its vast quantities of shellfish from rising acid levels, one imagines what else could possibly go wrong. Now the ocean conveyor system, important for carrying warmer tropical waters upstream into the North Atlantic is gradually growing weaker, with a circulation that hasn’t been witnessed in over one thousand years, according to a recent study in the journal Nature Climate Change.

So what’s behind all of this, and should we be worried? It seems as though we have enough on our plate as it is, if we’re already looking at fixing the current troubles. Well, the cause is one we’ve been aware of all along. Ice in the Arctic Ocean up north was already at record lows this winter. The resulting cold water seceding away from Greenland’s sheet of ice is slowing down the circulation of the ocean to levels not experienced since the High Middle Ages, according to the paper, an age that also consisted of a considerable warming period before slowing down in the 14th century AD.

The study obtained its data from coral samples, which are subject to bleaching and gradual death due to increasing acidity levels in the oceans across the globe, as well as from ice cores and tree rings to index the Atlantic winds’ long history of depreciation. The research also made use of the sea-surface temperature data found in previous studies (which are often more telling than surface temperatures) to create a new index — one which marks a trend of decline in the Atlantic meridional overturning circulation (AMOC). You might never have heard of it, but it’s one of the most important circulation systems on the planet – crucial for distributing the density of ocean water. Think of it as the ocean’s air conditioning system, bringing cooler waters to the deeper Atlantic and warmer waters northward, critical for the functioning of the vast majority of the Atlantic’s ecosystems in sustaining plant and animal life.

According to their data, there already was a powering down of the AMOC that took place in modern times, indicating a depreciation between 1970 and 1990, that scientists have already found. A partial recovery has happened, but not anything significant enough to bring the ocean’s current back to what it was in the days before the Industrial Revolution. It could be another irreversible effect of climate change – something that can’t be fixed even if we successfully do reduce CO2 levels.

The research was conducted primarily by the Potsdam Institute for Climate Impact Research of Germany. If their unfortunate forecast is upheld in future studies, it could suggest that as ice continues to disappear in the Arctic, the water it releases “might lead to further weakening of the AMOC within a decade or two, and possibly even more permanent shutdown of its integral components” warn the researchers in their paper’s conclusion.

While these findings might seem “dramatic” to you, as other scientists would agree, the numbers have shown to be consistent from computer climate models that other researchers have been projecting, according to Stephen Griffies, who has designed such models for the National Oceanic and Atmospheric Administration (NOAA.) Although Griffies did not participate in the study or the paper, he is no stranger to AMOC. A previous study in which he contributed was to one that linked abrupt changes in AMOC to a never before seen five-inch increase of sea levels along the Northeast U.S. coastline between 2009 and 2010. Bear in mind that 2010 prior to last year had set NOAA records for being one of the planet’s hottest years. He isn’t alone either. Previous research has shown a link between this same depreciation in AMOC slowdown with some of Europe’s harsh winters and even a spike in hurricane activity.

“It’s inevitable, from my perspective, that we will start to see more and more evidence for the slowdown of the circulation,” Griffies said. “If the overturning circulation slows down further, these extreme sea-level events on the East Coast will become more frequent.”

Michael Mann, prominent climatologist and the director of Penn State’s Earth System Science Center was one of the new study’s authors, in which he emphasizes that the rapid depreciation of Greenland’s ice is happening even faster than earlier researchers had projected, a possible explanation of why the winding down of AMOC is taking place at a rate “decades ahead of schedule.” The abrupt slowdown in the AMOC that took place in 1970 “looked like an aborted collapse” when compared with the rest of the data, giving us a rather unpleasant preview of what a “full-on collapse” may look like, a probable event that the next few decades might show us.

Many of you are wondering what, if at all, are the exact consequences brought about by a slowdown in the AMOC, with occurrences as divergent as higher sea levels on the Eastern Seaboard and European blizzards, so what’s the range of what to expect if the decline actually is irreversible? According to Mann, the consequences are somewhat hard to predict, but our own global food security is at risk. Not only do the currents provide ideal waters for the fish and mollusks we eat, but they need to move rapidly in order to provide the flora and fauna with the right nutrients for their survival. Withholding these nutrients can not only lead to a buildup of them in the deep sea, but also a complete disruption of the Atlantic Ocean food chain.

“The most productive region, in terms of availability of nutrients, is the high latitudes of the North Atlantic,” Mann said. “If we lose that, that’s a fundamental threat to our ability to continue to fish.”

While it’s been a staple of the argument of many climate deniers that extreme cold periods disprove the idea of a planet growing warmer, the AMOC could potentially cause parts of the Northern Hemisphere to become cooler. However, this is because the AMOC is no longer transporting warmer waters out of the tropics to different regions. The result of that, according to Mann, is that we could be looking at a sizable increase in hurricanes, Nor’easters and other types of storms, since they provide the hotter weather with new paths on which to travel. Already winters in the Northeast, and pretty much only the Northeastern United States have had colder periods than usual, wh

“If you shut down this mode of ocean circulation, you’re denying the climate system one of its modes of heat transport,” Mann warned. “if you deny it one mode of transport, it’s often the case that you will see other modes of transport increase.”

The new AMOC index “will certainly attract a lot of attention,” said Stephen Yeager, a researcher from the National Center for Atmospheric Research’s division of oceanography. Yeager, however, is doubtful over how reliable the temperature data used in the study actually is, suspecting that the circulation slowdown may actually be due to overall rising temperatures rather than a buildup of melted water from Greenland, and hopes to pursue it in further research.

“The paper presents an exciting new perspective,” Yeager said. “Many of the ideas put forth in this paper will require substantial further scrutiny and testing.”

James Sullivan
James Sullivan is the assistant editor of Brain World Magazine and a contributor to Truth Is Cool and OMNI Reboot. He can usually be found on TVTropes or RationalWiki when not exploiting life and science stories for another blog article.