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Why isn't the ocean full off massive plants? (lemmy.ca)
submitted 4 days ago by to c/asklemmy@lemmy.ml
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Only just realized this when watching a diving video.

But why isn't the ocean full of massive plants? The surface of the earth is covered is giant trees working to fight against gravity, wind, and fire.

But in the ocean you have little things like coral beds and sponges and maybe a kelp forest.

Seeing as weight is massively reduced, and the closer you get to the surface means more light, and water and nutrients are probably plentiful... Why isn't the plant life more massive? What is the limiting factor to things evolving to be bigger?

Only thing I can think of is CO2 perhaps?

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[–] [S] 10 points 4 days ago (4 children)

Yes but they are tiny.

I'm talking about blue whale type equivalent to aquatic plants. The biggest mammal on the planet lives in the ocean why not the biggest plant or fungus?

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  • [–] 3 points 4 days ago (1 child)

    Kelp plants can get pretty massive

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  • [–] 2 points 3 days ago* (1 child)

    That was my thought as well. But apparently they are known for their fast growth β€”the genera can grow as fast as half a metre a day (that is, about 20 inches a day), ultimately reaching 30 to 80 metres (100 to 260Β ft.

    So although they may reach a pretty impressive length, they seem dependant on sunlight like a previous comment pointed out.

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  • [–] 1 point 3 days ago (1 child)

    Yeah great point sunlight only penetrates so far into water, and plant life I think is classified as using photosynthesis

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  • [–] 1 point 3 days ago

    I'd imagine that plants need to grow big on land in order to be taller than the other plants to avoid competition for sunlight. In the water you can only go as high as the surface, and you didn't need to grow any bigger to get there, so microscopic plants won out. Why grow big and complicated if you can get all the sun you need by just being small and finding a little spot at the surface?

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