Let’s say you’re right:
(1) fish need 5 PPM of dissolved O2 (in round numbers) to live in relatively warm waters. Agreed. That does coincidently equate to your figure of about 5 mg/L. Deep ocean species need less, warm water fishes might need more. But we can go with the 5 mg/L figure. Apples and oranges. What’s your point? You have merely pointed out that methane CAN be a solute at higher concentrations than the minimum O2 levels required to support aquatic life. Relevance?
BUT...
(2) Methane is NOT toxic, nor is it suffocating as a solute in water. The mere presence of dissolved methane is NOT a problem. Please cite a reference for how methane directly harms fish. I don’t even know what “quite high enough” or “significantly biologically effective” means or why it is in quotes in your post. Again, demonstrate in fact that ANY concentration of dissolved methane (up to amounts encountered in the Gulf) is a PROBLEM. Being smug— (on my part) the concentration of H2O is highest of all! ... and that’s not a problem.
What is it you want me to agree to that I have not yet acceded to?
Again, my point on this post/thread is twofold—
(1) Methane, according to my sources is, expressed in moles per litre, among the least soluble atmospheric and/or aquatic/marine natural gases. and (2) I have yet to see how the mere presence of higher-than-normal levels of dissolved methane is a PROBLEM in the marine ecosystem because it is NON-toxic.
As an aside, you’ll note I prefer to employ a solubility number expressed in moles (micro moles actually) per litre, because comparing solubility by mass (mg) can be misleading due to the difference in molecular weight of 02 versus CH4.
Now I’ll move to your next post.
My point is simply that dissolved gaseous species, even though present at concentration levels of parts per million, can still be highly biologically significant.
And I'll say for the fifty-fifth time, I NEVER SAID METHANE WAS A PROBLEM. I don't see why you keep bringing that up.
"As an aside, you’ll note I prefer to employ a solubility number expressed in moles (micro moles actually) per litre, because comparing solubility by mass (mg) can be misleading due to the difference in molecular weight of 02 versus CH4.
One unit vs another. As a chemist, I certainly understand the "micro-moles/liter", but for the benefit of non-chemist lurkers/readers, I used the still valid but more easily understood figure of "mg/Liter", which is, even in the scientific literature, a more widely used and less confusing (to nonchemists) unit.
As to the rest of your suppositions, I'll wait 'til I have a chance to see the actual published peer-reviewed article over a newspaper summation. I'm quite well aware that, on subjects of science, reporters virtually always get one or more substantial points totally wrong.
On the overall subject of the Gulf oil spill, if you look back over my postings on the subject, you will see that I was one of the early advocates for NOT thinking "there's a spill in the Gulf, AND WE'RE ALL GONNA DIE".
Thus far, all the evidence points to my early comments as having been correct.