In a buffered system, the constituents of the system respond to changes in pH induced by addition of acid or base by altering their concentration to establish new equilibrium concentrations which result in only a small change in pH.
(Off the top of my head.)
Now, can you explain how a very weak acid will react in a buffered solution?
With my own personal coral reef, I must measure the quality of the water on a daily basis. For example, as the water evaporates, the salinity will increase. The pH of the saltwater is one thing that I never worry about.
In my living room, I have a two aquariums.
One is 90 gallons, and the other is 55 gallons. In the basement, I have another 300 gallons of saltwater that is constantly being circulated to the aquariums in my living room.
Maintaining a healthy fish population, while keeping my corals alive, has always been a challenge.
But have I ever worried about a change in pH, because of the CO2 from my breathing? You have got to be joking!
The pH of my saltwater aquariums is the one thing that does not change.
When hurricane Wilma sat over Cozumel for almost a week, everything was destroyed. My wife and I went diving there the following month.
All the the coral was covered with sand. Nothing was the same, and we feared that this coral reef had been destroyed.
Instead, everything was healthy, and if anything, this hurricane improved the conditions of life on the coral reef. The coral was nice and healthy, and we observed more "baby" fish than we had ever seen before.
Nature is absolutely amazing, if you simply stop and watch how it actually operates.