History is usually a great teacher for how living systems handle change. If
you'd like to follow up with this, I've photographed a graph to point out
times of rise and fall in the seas. This book is mainly concerned with how
things affected reefal development, but I thought the information here would
give you a good idea where to look.
The first is from page 186, Figure 5.23
http://www.farmertodd.com/nanfa/cretaceous/DepthChart.jpg
You'll see the highest points in the Cretaceous, some 350m higher than
current sea levels at it's peak. This period is believed to be plagued by
heavy volcanization (that's like the lava kind, not the Spock kind ;) which
left a whole lotta CO2 up in the air, and made for one big greenhouse. The
book suggests average air temps 10 degrees C higher than our current
averages. Phew!
It is supposed the world looked something like this from page 187, Figure
5.24
http://www.farmertodd.com/nanfa/cretaceous/MidCreataceousSea.jpg
I've added the current continent labels so this thing makes some sense :)
What I found interesting was that there was absolutely no thought given to
salinity differences in reef ecosystems in the text... But changes in fauna
had everything to do with turbidity from continental erosion from the
approaching waters. I wonder if the now aqueous minerals in the eroded
soils contribute to the overall salinity, and the volume of water doesn't
make much of a difference? That's the next thing I'll look for :)
All in all, as you can see from any research you do on how and how well
certain groups of animals were doing in this period... Speciation and
adaptation kept right up with the changes in environment. In this period,
while reef building coral were present and had been the dominant reef
builders prior, they took a back seat to mollusks who took on the task of
reef development during this time. My *guess* is with all the sedimentation
and liberated organics, there was an algal fest to end all going on :) But
aside from this guess, this period illustrates how speciation and adaptive
radiation works it's way.
The exclamation point on all of this happens at the end of the Cretaceous.
All thru these changes life adapted, and background extinction remained
constant. It wasn't until the end when some cataclysmic event happened (I
think this is the Gulf of Mexico Impact?) that caused a mass extinction.
I'm unfortunately not seeing what the total losses were in biodiversity...
Perhaps someone else has that information more readily available.
There are some, as you might be thinking now, other implications to our
current situation etc... But I think this is where I'm straying to unholy
ground. ;) I'm open to discuss, but only if people promise to look at this
as they type responses:
http://www.farmertodd.com/nanfa/cretaceous/ToddRash.jpg
...and realize that I'm never in a place where I take myself too seriously.
I'd really hate to start an argument because email is imperfect and folks
can't see my big stupid grin :)
Hope you're enjoying all this John. I certainly am. I needed something new
to obsess about :)
Now... To get that BAP thingie done so y'all, like the good Dr. Stallsmith,
can put in all these spawnings yer gonna do this spring :)
Todd
----- Original Message -----
From: "Todd Crail" <farmertodd_at_buckeye-express.com>
To: <nanfa_at_aquaria.net>
Sent: Monday, March 03, 2003 11:04 PM
Subject: Re: NANFA-- Louisiana sinking and other thoughts
> > 3. What effect would rising sea levels have on short term and long term
> > biodiversity of fish? If there is significant warming, then there would
> > be a reduction in salinity due to retreating polar ice and glaciers.
> > Someone recently said that Red fish have successfully colonized fresh
> > or estuarian waters. Would we expect to see more of that? Would a
> > reintegration of teleosts occur resulting in completely new
distributions?
>
> I'm up for some speculation, and a great thought, I'd like to join in on
it.
> :) Given that I am no expert on the subject, but have read quite a bit on
> adaptation, historical events of crash, divergence and adaptive
radiation...
> (read: this is not the gospel truth in any way ;)
>
> My quick answer would be yes and then no, and topped with some "You'd need
> to live to a thousand to see anything significant". :)
>
> Yes, in that you would see species making their very best efforts to
survive
> given any change in conditions. Short term it would be redistribution.
> Those who have the ability to make the changes more gracefully will carry
> on. Those who do not, pass on into the extinction record. I wouldn't
> speculate on who would take over where... Maybe estuarine species
expanding
> a wider range due to the extensive shallows created... Maybe marine
species
> just expand with the shoreline progress inland. There's really no way to
> predict that.
>
> No, in that I don't think it will be much of a "redistribution" for very
> long. I seriously doubt that you will have a mass of the current species
as
> they appear today in the same form over a period of time. I feel that
they
> would be at first, of a divergent genotype, if not even more so, a unique
> species, and certainly so in the future. It would be interesting to
compare
> DNA of landlocked Salmon in the Great Lakes with their native range "look
> alikes" or a population of Striped Bass in a Tennessee or Arizona
reservoir
> with fish up East in the sea. I doubt they'd come out the same... Even
> after the 50 or so years they've had different conditions long enough, I
> would think, to make some difference somewhere. The situations are
> different, the competition is different, everything is different... And
> different, historically, produces different genes. And so that isn't
really
> a redistribution. That's speciation.
>
> The timeframe, I think speaks for itself :)
>
> Your salinity comment has me wondering and my interest peaked, and I'm
gonna
> hit the books this week to see if there's already a defined answer. I
> vaguely recall that the dilution will not be significant enough, nor quick
> enough to cause a mass extinction, and would create the short term
> redistribution, long term speciation. Due to the way temperature affects
> salinity, I again, vaguely recall reading that as the oceans balance out
> their new climatology, that there isn't that great a percentage change.
May
> need to go pick up an oceanography book for that one tho...
>
> But in the sprit of speculation... I'm concerned that any slight change
will
> modify hermatypic reef building by coral in such a way that the dominant
> reefs and obligate inhabitants are gonna go the way of the Dodo. They're
> already in trouble for a variety of reasons. It would be sad, but
> interesting, to observe how those species would adapt. Guess we'll have
to
> save that one for the Meerkat's species line to answer, no? :)
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