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Comment by nradov | Hacker News Reader

Sea grass already grows pretty much everywhere it can grow, so I don't think we can cultivate a lot more (at least not without disrupting other sensitive marine ecosystems). It's more important to prevent pollution that would kill existing sea grass.

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Have you got a reference for that?

This article suggests that "92% of the UK’s seagrass has been lost in the past two centuries, with 39% disappearing just since the 1980s, thanks to pollution from industry, mining and farming, along with dredging, bottom trawling and coastal development."

https://www.theguardian.com/environment/2021/nov/05/seagrass...

What are the limiting factors for it's range? Is there a critical nutrient that can be introduced?

It is grass. It needs sunlight and a substrate on which to grow. That means shallow/clear water over a sandy bottom, not a common thing in the ocean.

Seems like sunlight and substrate is much more common than seagrass is. I found this paper [1] that talks about the difference.

It estimated the area of suitable sunlight and substrate to be 4,320,000 km2 but estimated seagrass coverage of 177,000 km2.

I think this big difference indicates that there are additional factors at play.

https://iopscience.iop.org/article/10.1088/1748-9326/ab7d06

Earth has something like 150 million square kilometers of ocean. 4mil is a tiny corner of that area. Depth/light remains by far the primary limitation for sea grass, preventing it from even attempting to colonize the vast majority of the worlds oceans. Compare other carbon sinks like plankton which can exist across the ocean irrespective of water depth.

Sure, but Im not asking why seagrass doesn't cover the entire ocean or entire planet.

I'm asking why it doesn't cover more area than it currently does it appears that light and substrate is an insufficient answer. 90% of the area with suitable light and substrate is not covered, so something additional is going on.

> What are the limiting factors for it's range?

Fishermen and recreational sports

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