I think the point of the article is that understanding how seagrass captures carbon is useful and interesting.

For more relevant numbers, I did a very quick calculation (tell me if you spot a mistake).

Using these numbers [0, 1], the worlds seagrass captures ~5% of US automobile emissions per year.

Another number of interest, the amount of seagrass carbon sequestration is 2 - 4x greater than mature tropical rainforests (per hectare) [0].

Seems to me that seagrass is an organism worth understanding.

[0] https://www.thebluecarboninitiative.org/about-blue-carbon

[1] https://www.statista.com/statistics/1120499/us-road-vehicle-...