Everyone please stop blaming coral bleaching on climate change. Nitrogen run-off from farming is the main cause. We need to reduce nitrogen enrichment in farming, which will lead to lower yields and lower profits (or, more likely, higher prices). But blaming climate change here is an egregious example of green washing which will prevent or delay resolving the real issue. Stop it. Please.
"Anthropogenic nutrient enrichment is often associated with coral reef decline. Consequently, there is a large consent that increased nutrient influxes in reef waters have negative longterm consequences for corals"
https://www.sciencedirect.com/science/article/pii/S187734351...
"Increased loadings of nitrogen (N) from fertilizers, top soil, sewage, and atmospheric deposition are important drivers of eutrophication in coastal waters globally. Monitoring seawater and macroalgae can reveal long-term changes in N and phosphorus (P) availability and N:P stoichiometry that are critical to understanding the global crisis of coral reef decline"
https://link.springer.com/article/10.1007/s00227-019-3538-9
No. Nitrogen pollution has local effects and is an enormous problem in some important fish spawning grounds, but it cannot explain what happened to the Great Barrier Reef in 2018 and again in 2019.
The effects of temperature on corals are getting to be quite well understood now. Globally, marine heat waves are a major problem, alongside pollution and direct reef destruction.
Likewise, ocean acidification is happening as part of "climate change" (carbon pollution) and is another stress for corals.
I agree with your point about N runoff. We need to stop growing maize for biofuels and animal feed and implement megascale riparian planting programmes to limit the damage done by floods. For starters.
These things are not either-or. Overfishing and destructive fishing practices, "development", various kinds of pollution and oxygen depletion ... we're doing it all, and it all affects reefs.
Your sources don't seem to exclude warmer waters as a contributor to bleaching. From your first source "...recent scientific results show that increased nutrient levels can reduce the heat stress tolerance of corals..." So it seems that runoff + heat both contribute to coral bleaching.
I'm not sure we can make this conclusion. Certainly the effect you're mentioning does extreme damage but it is localised. Acidification is nowhere near as localised, therefore whilst it doesn't affect individual areas as strongly it is much more widespread. When looking at the accumulative effects the question of which one is worse is up for debate and non trivial to answer.
I have tried to explain this here, but they don't want to hear it, if it does not put climate change as the #1 reason. My daughter is in coral research, N:P is the poison, heat increases it's potency, without the N:P the heat alone does not bleach the coral. We see coral bleaching in all areas where agricultural sits above the wetlands and the runoff runs into the wetlands and then over the reefs. It's funny how Australia's wetlands and Florida's everglades are so similar, and sitting right above both of them is large sugar farms using tons of fertilizer pumping tons of N:P into the wetlands and then out and over the reef.
"Anthropogenic nutrient enrichment is often associated with coral reef decline. Consequently, there is a large consent that increased nutrient influxes in reef waters have negative longterm consequences for corals" https://www.sciencedirect.com/science/article/pii/S187734351...
"Increased loadings of nitrogen (N) from fertilizers, top soil, sewage, and atmospheric deposition are important drivers of eutrophication in coastal waters globally. Monitoring seawater and macroalgae can reveal long-term changes in N and phosphorus (P) availability and N:P stoichiometry that are critical to understanding the global crisis of coral reef decline" https://link.springer.com/article/10.1007/s00227-019-3538-9