I believe I've seen that movie
But I believe they stressed more on pollution into the rivers and those pollution going into the ocean which provides too much silt and killed the reefs.
Most of the bleaching occuring now is due to high ocean temps from I would guess the green house effect
Not to take away from any concerns like run off, siltation, etc, but it can't be forgotten that bleaching events are the reefs way of clearing the area for regeneration, much like forest fires are needed to maintain a healthy forest in the long term.
In our minute time frame of looking at things, a forest fire is often reported as a disaster, much like when Mt. St Helens erupted and leveled 1000's of square miles of forest... it'll be back and more dynamic then before the eruption.
Good point--massive die offs actaully increase the amount of diversity in a given ecosystem. When an area has been established for some time, the competition for ecological niches has to some degree run its course, and the "winners" outcompete the "losers", limiting the number of species there. Wehn an area is wiped out, it's fair game for all new colonization and many new plants and animals come in and battle it out.