The lakeshore I live near is sometimes sandy, sometimes rocky. The wind shifts and we either get a few inches of sand deposited, or it's all stripped away and we're left with rocks.

That must be happening all around the gulf. A layer of tar is exposed and everything changes.

Then there's the lifecycle issues. A population of fish swims upriver and spawns, expecting to find fresh shrimp to eat. There are none, so the whole new generation dies.

Then of course the bacteria and algae eat the dead fish and create an anoxic bubble that drifts downriver, killing everything along the way.

Yeah, this is going to suck hard for years.