Comment by timschmidt
6 hours ago
Algae are the bottom of the ocean food chain. Everything interacts with it. But algae's happy to grow in a bowl of water left in the sun.
Lots of things eat krill and small fish. They're near the bottom of the foodchain too. In addition to algae, krill are opportunistic omnivores who often consume detritus. But their primary diet is algae. Small fish tend to be pretty similar.
It's not that other things don't interact with algae or krill or small fish, it's that those groups are the foundation bedrock of the ocean ecology. And single celled organisms like algae are tough as nails in aggregate. Couldn't kill them all if we tried. Pool owners will be familiar with the struggle.
But it's not a bottom up interaction. If whales are killed off from climate change, then those other things can get out of control. Too much algae, and then you have hypoxic environments.
A perfect example of this is when sea otters were nearly hunted to extinction which caused sea urchins to flourish which caused the death of coral and coastal environments which started to affect the larger things that depended on those environments.
My point is that any change to the careful balance can have non-linear effects.