quote: but will survive indefinitely in that medium if gradually acclimated to it.
Is that consistent with a sudden, global deluge? It doesn't seem so to me.
It seems to me that this crys out for quantification. How long, days, hours, weeks in "gradually" in the first one? ANd how "sudden" is the second?
As far as speciation: We're finding different mechanisms all the time of rapid speciation that could have happened post-Flood. For example, introns (usally labelled Junk DNA) could have played a role. Depending on where the cell begins transcription, different genes can be produced. The founder effect also stimulated variation, for example it alters pleiotropic balance, and founder populations have a great range of variation. Inbreeding depression would have selected for animals that would have been more fit early, also. Genes are highly interactive, and rapid post-Flood variation would have been possible.
Certainly, we understand that evolution can happen pretty quickly under some circumstances. But there are at least a couple of problems with the idea. 1) The raw speed of the speciation. I've seen some creationist sites that have "kind" at the family level. For there to be no historic record of this happening the full range of speciation would have to have been complete sometime well before 2000 years ago.
2) Why did it stop? There is no suggestion of a mechanism that can turn on and off that extremely.
I'm afraid that an arm waving explanation like this isn't going to hold up under any kind of close examination.