It always comes back to the same issue: a fantastically increasing human population. Virtually everything stems directly from human overpopulation. Overfishing on a small scale, massive commercial overfishing using destructive technologies, vast quantities of farm fertilizers washing into the seas, construction which destroys natural shorelines, and countless numbers of other actions, are all designed to feed or house a population which grows by millions every week, and at a faster pace every day. Climate change, acidification of the seas, and ocean stratification are ultimately caused by the same kinds of population and consumption imperatives that caused the recent spectacular but in the long run less permanently destructive gulf oil spill.
Only if we as a species are prepared to dramatically decrease our numbers through serious restrictions on the numbers of children permitted, and accept the social and economic upheavals that will cause, can anything be done to save what is left. Perhaps, if we really deprive ourselves, in may be possible to reverse some of the damage. As was pointed out, we are a selfish and shortsighted species, so I'm not optimistic. Without drastic population control, anything and everything done in the name of conservation is futile, an illusion that can, at best, put off the inevitable by a few years. Big deal.