How does the ocean biome collapse?
August 8, 2012 6:02 AM   Subscribe

I have a very broad question about the expected collapse of the ocean biome, and a bunch of related detail questions.

So first, the general question. I am kind of assuming that based on climate change, collapse of the coral reefs, overfishing, etc etc., that some time soonish the ocean biome is going to collapse. Where can I find resources online that outline how scientists / biologists project that this will play out?

If you are someone with specialized knowledge in this area - marine biologist, climatologist, ecologist, etc. - I'd like to hear your own prognosis and opinion for how this will play out, as well. Specifically:

Once it starts, does it snowball very rapidly? What is very rapidly? Does it go from plenty of fish to empty desert in a couple years? A couple decades?

What comes after? Does the ocean change chemically or temperature wise in such a way that fish life is completely wiped out? Or is it just that the carrying capacity is much reduced, and there are fewer / hardier species of fish?

Are there dramatic waves of change? Like for example, a few years of massive algae blooms that choke the oceans of O2, or some other species like jellyfish completely take over?

Do sea plants / seaweed survive in any numbers?

Does it eventually reach some new equilibrium, with a new ecosystem establishing itself? Or is the more likely case complete dieout?

Do you project anything else strange / interesting happening that I have failed to consider above?
posted by Meatbomb to Science & Nature (5 answers total) 14 users marked this as a favorite
Over the course of the history of the planet, there have been many times in the past when there were ecological catastrophes which utterly dwarf the one you're worried about. And though they may have led to reductions in diversity in the oceans, they didn't result in a total biome collapse.

The fish survived the K-T asteroid impact, for instance.

The ecological history is very clear: ecological systems are very robust. They don't tend to snowball; you don't get cascading failures.
posted by Chocolate Pickle at 6:08 AM on August 8, 2012 [1 favorite]

Best answer: I don't have specialized knowledge, but I've done a fair amount of independant research since I do a lot of environmental volunteerism and this is a strong concern of mine.

What I have been led to believe is that as climate conditions change, niche species that thrive under those conditions will flourish while existing species die out. Specifically, most of the literature I've read suggests that jellyfish will inherit the oceans.
posted by wolfdreams01 at 6:38 AM on August 8, 2012 [1 favorite]

Best answer: The ecological history is very clear: ecological systems are very robust. They don't tend to snowball; you don't get cascading failures.

No. At the very least you have to caveat these wide, sweeping statements.

To push some credentials up front: I'm an evolutionary biologist who used to work with ecologists, in particular on extinction and macroevolution. I no longer do that, but keep a eye on the field.

First, what will or can happen in the seas? We can plausibly argue for a lot of different scenarios. As far as evolution and ecology go, marine life has been little studied. There's lots of unknowns.

Ecological systems are very robust? What does that mean? We've had a number of very big, devastating extinctions, that wiped over over 90% of taxa. In as much as something came back, yes, you could say ecology is robust. In as much as the succeeding ecologies were totally unlike what went become, the ecology was not robust at all. New ecologies developed.

Complete dieout is unlikely. What is more likely is a rise in survivor forms, generalist species that through sheer numbers and adaptability can wait out the changing conditions, until things stabilize long enough to allow the evolution of specialists. Sometimes we call them "weeds". And there are indications - from land ecosystems anyway - that such "weeds" are spreading. Sea weed and jellyfish are generalists (in general), we're likely to see them hang around.

Rapid? Rapid in geological or evolutionary terms, sure. Rapid in human terms is less likely.

A new equilibrium? Probably. How long is unclear. Studies of completely sterilized ecosystems show a rapid repopulation (from survivors in the outside world). Total recovery takes longer. Of course, if there are survivors to flock in and repopulate, you may end up with something that looks like the original ecology. If there are no survivors to do this, who know what may result.

Will it snowball? Arguable. There are plentiful arguments about the mode of evolution and lots of controversy. There's one school that says ecologies are robust within certain limits - past those limits and things fall apart. There are others that argue for a more dynamic view, where is set off-balance the system could rapidly change until it finds a new equilibria.

You've asked a lot of questions, this will do for a start.
posted by outlier at 7:25 AM on August 8, 2012 [14 favorites]

Response by poster: Hey outlier thanks so much. You are exactly the kind of person I was hoping might contribute here.

If you are willing, I'd really love some more from you!

On the idea of 90% taxa dieout / generalist species winning out. If I understand, this could be seen as a "death of complexity". Generalists will tend to be more hardy and not so reliant on very specific ecological niches to survive, right? What would you put forward as some likely generalists that might thrive / take over in a catastrophic dieout type scenario? Are jellyfish one of these candidates, and what makes them more resilient / more likely to survive in these times?

The "snowball" idea - if some of the base food chain animals like krill / plankton don't survive, that cascades through the food chain. But are these tiny animals likely candidates to suffer in a catastrophic collapse scenario? Could we assume that higher level predators at the top of the food chain will be gone?

I am really interested in the idea of a change in ocean chemistry that I asked in the original question, if you are up for it. Will people always be able to get (at least some) food out of the oceans, or are there possible scenarios in which the chemistry / conditions change to such an extent that all there is for us is jellyfish and plankton, or some other unpalatable gunk?

Again, thanks very much for sharing here outlier!
posted by Meatbomb at 1:14 AM on August 9, 2012

Best answer: No problem. Just insert big caveats that this is not my current research area and I am not and was not a marine biologist. Also insert caveats about the limitations of research into paleontological extinction and ecological collapse. They're hard things to study.

You could look at generalists / survivors winning out as "the death of complexity", although complexity is a very ill-defined term. Better to think of it as the "death of specialists". I'm a little reluctant to nominate specific organisms - my work was largely on land-bound ecosystems - but look towards creatures that are (1) abundant, (2) widespread maybe with a refuge ecosystem they can retreat to and re-emerge from, (3) smaller and (4) tend to reproduce prolifically. (Although I see there's at least one paper that suggests abundance may be irrelevant.). Jellyfish are a plausible candidate, as are many sea plants. Shelled creatures survived previous marine extinctions quite well, so many we should expect to see them do it again. Just about anything large (which tend to be specialised and at the top of the food chain) would go. It would take a helluva kick to kill the stuff at the bottom like krill.

(I should underline here that I don't know that a major marine collapse will happen - this is just a guess at what it would look like if it did.)

I think this takes care of your first two questions. I'm a little uneasy about venturing opinions on a change in ocean chemistry. I seem to recall this has happened a few times in Earth's history, but accompanied by changes in the atmosphere / climate etc. So, if a change in ocean chemistry did occur, we'd likely have bigger problems. I don't want to overstep my knowledge so I'll stop there.

As an aside, I've gotten into discussions about extinctions with lay people, and there's a common viewpoint that since Earth has had major extinctions before and survived them, what's the problem with contemporary extinction? Which is akin to saying that there are still people alive in Afghanistan so it's can't be _that_ bad there ...
posted by outlier at 5:01 AM on August 9, 2012 [1 favorite]

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