How would marine plants lower global warming?

Question

How would marine plants lower global warming?

Answer 1

they remove CO2 from the atmosphere just as all plants do when they photosynthesise.

Answer 2

They could fix carbon as organic matter and then remove it from circulation when they (or the things which eat them) die and fall to the ocean floor.

Answer 3

i dont think they would actually lower the problem, but they would help lower the ocean level. marine plants drink the ocean water. it doesnt seem like they'd do all that much, but with more of them they could at the very least prevent the water level from getting much higher.