Do you like to eat, or would you rather starve? If you're a swordfish or bluefin tuna and you like to eat, you got some bad news today. Your chance of starving is going up; ocean areas where food is scarce are getting bigger.
Maybe we should start selling satellite-linked GPS units to fish so they can download daily food maps and make a living.
Now wait a minute, you're saying, this is hard to keep clear. Dead zones and deserts, excess nutrients and low nutrients, it's a mess and maybe it'll all just balance out.
This is different than dead zones, and yeah, it's confusing. So please pay attention even though there's a brief scary science blurb cmoing.
Some ocean areas have rich biological productivity, and some don't. The black areas above right are the "don't" areas where food is scarce. They're called gyres and you can tell when you're in one because the water is clear, really-really clear. Like 100 foot visibility or more. Oceanographers will tell you this all happens becaues of wind, currents, and "down-welling" which result in low levels of nutrients. These low productivity areas are getting bigger (red part of the maps below right).
The scary news is that the low productivity areas have expanded substantially in the last decade. If this is part of a long-term trend, we should probably be worried. The research says it's probably linked to climate change, uh-oh. But since this is new stuff, there are some who say links to climate change are unproven (see note at bottom of link).
Proof, harumph. We need it, but if we're smart we won't wait until we lock up all the details, cuz those little rascals are REALLY hard to pin down.
We do seem to be forcing ocean extremes to get more extreme. Some food-rich productive areas are tipping over into eutrophication and dead zones. Some low productivity food-scarce areas are growing. This could undermine the fish and other animals that we rely on for food. It's an ocean future that we didn't plan and we probably won't like, and we should get moving in protecting the things we like. It's simply prudent.