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Why isn't the ocean full off massive plants? (lemmy.ca)
submitted 3 months 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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[โ€“] 4 points 3 months ago* (4 children)

Water pH (water in the ocean is alkalyne, different from the varied soils we can have), water dynamics and currents (whater moves, soils do not), temperature delta (the deeper it goes, there are different temperatures), source of nutrients (carbon cycle on the different soils we have vs the ocean nutrient cycles), sunlight availability (sunlight might change based on the particulates present on the ocean, in different seasons, etc, in a higher variation than above soil), etc. Ocean dynamics is very different than continental dynamics (or island dynamics).

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  • [โ€“] [S] 2 points 3 months ago (3 children)

    All of those variables to me appear like they would be similar on land. Currents move but so does wind, and I don't think their are any currents in the ocean that can rival hurricane force winds that trees can contend with.

    Sunlight also changes quite a lot on land depending on the season or weather.

    Just can't see why underwater trees aren't a thing.

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  • [โ€“] 3 points 3 months ago (2 children)

    The chemical structures that make a tree a tree would be very different, lignin and cellulose will act different on alkalyne environments, pulping for paper uses very alkalyne (like pH 13) solutions to change the chemical bonds that make the wood "hard", turning them into loose fibers. Also water infiltrate cellulose, so osmotic pressure, ion pressure, etc, would change how the tree structure would form.

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  • [โ€“] [S] 2 points 3 months ago (1 child)

    Well, ya but I don't think it would be 100% identical to trees. Lignin didn't really even exist for millions of years before trees evolved to fight gravity on land. But underwater you wouldn't need a strong trunk like that since they would weigh so much less and can evolve buoyancy structures or something like other plants do. Or even short and stout, just massive.

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  • [โ€“] 2 points 3 months ago* (last edited 3 months ago)

    From what I searched, cellulose from kelp is different from cellulose from trees, from a properties perspective, so it seems it only acts this way on land is because it's on land. Maybe the need for a stronger material built trees for them to be the way they are, not having a need for a strong trunk can make an inpact on the evolutionary path of those beings.

    It could be that the environment primed trees to need this structure, while ocean beings never experienced the evolutionary force to build some structures in the same way.

    Idk, I'm not a biologist.

    Edit: So the chemical and physical environment not encouraging the evolutions teps needed for trees to form in the ocean.

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