Algae First To Recover After Asteroid Strike 86
pickens writes "The asteroid that impacted earth 65 million years ago killed off dinosaurs, but microalgae bounced back from the global extinction in about 100 years or less. Julio Sepúlveda, a geochemist at MIT, studied the molecular remains of microorganisms by extracting organic residues from rocks dated to the K-T extinction (in this research referred to as Cretaceous-Paleogene), and his results show that the ocean algae community greatly shrunk in size but only for about a century. 'We found that primary production in this part of the ocean recovered extremely rapidly after the impact,' says Julio Sepúlveda. Algae leave certain signatures of organic compounds and isotopes of carbon and nitrogen; bacteria leave different signatures. In the earliest layers after the asteroid impact, the researchers found much evidence for bacteria but little for algae, suggesting that right after the impact, algae production was greatly reduced. But the chemical signs of algae start to increase immediately above this layer. A full recovery of the ocean ecosystem probably took about a million years, but the quick rebound of photosynthesizing algae seems to confirm models that suggest the impact delivered a swift, abrupt blow to the Earth's environment."
Old science (Score:3, Interesting)
There is lots of skepticism that the asteroid strike "killed off [the] dinosaurs." I saw a study where a microbiologist claims that many factors contributed to the death of the dinosaurs, but mostly it was disease, a competing lifeform that grew rampant well after the strike. I don't remember his name because it was a TV show, but I'm sure you can track it down.
In the meantime, this is all I have to offer from the Google:
http://blogs.discovermagazine.com/80beats/2009/04/29/new-study-casts-doubt-on-the-asteroid-strike-theory-of-dino-extinction/ [discovermagazine.com]
At this point, because of the data we have available in the sediment record, the idea of the dinosaurs being destroyed by the asteroid strike is almost mythology. Keller's work has gone a long way to confirming that we still don't really understand exactly what happened.
--
Toro
Relevant paper in Science (Score:5, Interesting)
I wish journalists would be more diligent about actually citing the relevant paper [sciencemag.org] from which the news releases are derived. If it is on the web, is it *that* hard for people to stick a link in there?
Anyhow, I haven't read the paper because I can't get the full article yet, but if some of the recovery they are interpreting after the Cretaceous is related to dinoflagellates [wikipedia.org] (which can be detected as dinosteranes [doi.org] in organic geochemistry work), it wouldn't be surprising that they bounced back fairly quickly: A) many of them form highly resistant cysts [wikipedia.org] as part of their life cycle, and those cysts can survive for years before "hatching" and going back to business as usual, B) many dinoflagellates are heterotrophic [wikipedia.org] or mixotrophic [wikipedia.org] -- i.e. they eat things or they eat things at the same time as using photosynthesis. As a result they could probably survive better than many other planktonic "algae" that are exclusively autotrophs [wikipedia.org] (i.e. photosynthetic). This expectation is confirmed to some extent by the observation of relatively few dinoflagellate extinctions across the K/T boundary compared to many other planktonic organisms.
Re:Wow, fascinating. (Score:5, Interesting)
But what makes paleontology relevant to our daily lives? The study of mass extinctions is really important: we can't do the experiment of killing 50% of the earth's biota or clouding the skies for ten years to see how life responds. But, as humans, we are radically altering ecosystems with negative effects which may not play out for thousands of years. We need to understand, having already killed off a massive number of species, how life on earth will respond. Furthermore, understanding the oceans, particularly unpreserved organisms like soft-bodied algae, is important to understanding the processes which control the atmospheric content and the supply of nutrients to larger sea creatures. For example, we know species richness recovery from the KT was delayed in some places for periods much longer than a century. Some thought that was due to a prolonged lack of food. Now we know that the algal production started up so quickly, we know that can't be due to a lack of food; maybe its something else (like a wrecked ecosystem structure).
If you need to know any reasons why understanding the past is important, look up the papers of Jeremy Jackson or David Jablonski. They'll set you straight.
Re:Wow, fascinating. (Score:1, Interesting)
This is a valid question and should not be marked "troll". It is a question that deserves a serious answer.
Another paleontologist has already answered it well, but I'll give my take as a fellow paleontologist.
The main point I make in the classes I teach is based on an old saying:
"Those who do not know history are doomed to repeat it".
In the case of life, that history is mostly one of extinction -- the destiny for >99.9% of species that have ever lived. Humans are a species of life, so do the math, but wouldn't it be nice to "beat the odds" for a while?
Life on Earth has been through a heck of a lot, so I suppose the extinction statistic isn't surprising. There have been some very bad days on Earth -- days that are on par with Dr. Strangelove "doomsday" scenarios, but naturally caused. From paleontology we know that life will survive in some form even when things are extraordinarily bad, although it takes a while for the global ecosystem to get back on its feet afterward, which is what the cited paper is about.
Would we know about these natural hazards to life on Earth if it were not for paleontology? Probably many of them, yes. There are other ways to get at them. But it is only via paleontology that we can get a sense of the effects on life -- the response to the stress. As I also point out in classes, even if it were practical to whack a 10km asteroid into the Earth to see what would happen, it is an experiment we would not want to run. Fortunately we have a bunch of experiments that were already run, and it is more than just impacts:
What happens when ocean currents change configuration?
What happens when the oceans become more strongly "stratified" into layers ("Strangelove oceans [nature.com]")?
What happens during volcanic eruptions 100x greater than any in historical times?
What happens when sea level goes up or down?
What happens when half of whole continents are covered with glacial ice sheets?
What happens when whole groups of organisms become extinct?
What happens when atmospheric temperatures or compositions abruptly change (e.g., the Paleocene/Eocene Thermal Maximum [wikipedia.org])?
All of these are highly relevant questions to the long-term survival of humanity because they could happen naturally or, in some cases, analogous processes could relate to human activity. They are tough questions to answer, but we are fortunate to have access to previous changes that far exceed what we expect in the near future. If we are going to become extinct like most other species have, I'd rather go out knowing that I tried my best to understand and cope with the world that I live on rather than dying out because I was ignorant of my environment and the implications of decisions related to it. This is stuff we need to know. Ignoring it is like living in a house while knowing *nothing* about how to maintain it.
You can always question the priorities of a field of study as obscure as paleontology: is it more important to invest in, say medical science or the development of new energy sources instead of paleontology? You ask this question specifically, and you are right to ask it. Even though paleontology bears on the long-term survival of humanity, which is kind of important (!!), it might be hard to justify with so many urgent problems. I agree that medical science and energy are more important. But my answer is a fairly simple one: have you actually looked at how much money is invested in paleontology versus those other subjects?! ;-) The relative financial priorities aren't out of line, as near as I can tell.
PS: as it turns out, quite a few of the mass extinction events in Earth history are associated with changes in ocean circulation and phytoplankton productivity, which sometimes results in the deposition of organic-rich marine sedimentary rocks. A well-known exam