This is a complete misunderstanding of the chemistry involved.

Increased dissolved CO2 concentrations (pCO2) make it much HARDER, not easier for corals and shellfish to fix calcium carbonate.

The reaction is:
Ca2+ + 2HCO3- CaCo3 + H2O + CO2
This reaction can go in either direction. It needs to run from left to right to create coral and shells. Increase the concentration of CO2 in the water and you increase the pressure in the other direction (right to left, i.e. dissolution of CaCO3 rather than accretion).

No. http://www.fairwork.gov.au/

I see the email to HR and the council as self-righteous and attempting to undermine my authority.

I see a "reply all" in a situation like this as friendly and open discussion - as long as it is diplomatically worded and not in legalese. A private email to me or (separately) to the person who sent the email would also be good, but further action would then be needed to undo the damage. If was anonymous, it would signal a lack of trust, which I'd find disturbing, but understandable.

The question isn't whether you have sympathy for the companies and individuals who will be directly affected. The question is: how much will YOU be affected by all the companies and individuals who are too lazy or ignorant to take steps 1,2 or 3? Might you have given your credit card details to one of those companies? Might you depend on another in some business sense? Might a few tens of thousands of those individuals have their computers turned into parts of botnets that will be used to attack your systems, or systems you rely on?

Sure they can. They can give lukewarm (accurate but unenthusiastic) performance evaluations and references. They can choose not to put your name forward when asked to identify rising stars to whom others in the organization should be paying attention. They can listen less carefully to the proposals you put forward and give your training requests just a little less priority. They can not invite you to after-work drinks where you'd hear about opportunities ("Z will be putting out a call for proposals next week - get started now if you have an idea, because you won't have much time once the call goes out") or the kind of office gossip that could help you to work around office politics (e.g. "X doesn't get on with Y, so don't get Y involved if you want X's support on a project"). It happens all the time. It can happen without them even setting out to give you a hard time, or realizing that they are doing it. If you don't get out quickly, it's enough to jettison a career.

I guess you'd need to know the personalities involved.
If someone on my team sent the email you suggested, I'd tag them as hostile, difficult to work with, not to be trusted, and a game-player. Yes, I'd be scrabbling to put out the fire and make sure Marketing knew it had done the wrong thing, but I'd also be looking for ways to avoid having to rely on the person who had sent that email in future. Am I oversensitive? Perhaps, but I'd be anticipating trouble from them.

If someone on my team sent the version I suggested, I'd say "Yeah, good catch. Thanks." I'd make sure it was passed on to whoever had sent or received the original email, if they hadn't already seen it and hope that was the end of it. Am I working in an organisation that would encourage astroturfing in the first place? No, but I have to believe that most people in management even in those companies - like most people anywhere - are just trying to get by and do the right thing.

This strikes me as a very aggressive email and would only be appropriate if the work environment is already strained and management has shown that it can't be trusted to handle suggestions or discussion in a fair and open manner. Escalating the matter to HR and the general council before even opening a discussion is hostile.

Better to clarify first, go in friendly and assume ignorance rather than evil is behind the request. Maybe "reply all" something along the lines of "we might want to be careful since this could be seen as astroturfing [link to wikipedia article]. Honest recommendations of the app from those who use it are a good, but let's not go too far."