So it turns out that there’s billions of Coca Colas’ worth of sugar released into the rhizosphere beneath sea grasses.


I have a race of humans/superhumans/merfolk that live exclusively in the sea and other aquatic habitats. They very, VERY rarely leave the sea/water unless they absolutely have to. They're very humanlike in appearance with only some visual quirks like webbed hands, long flexible feet, somewhat fatty foreheads to behave as melons, etc. and other internal traits like cetacean-like blood, collapsible ribs, etc.

At best they live in houseboats (of varying types) and make temporary living spaces on makeshift rafts, diving bells, etc. Being an amphibious species, their palette is limited (from a land-lubber’s point of view) outside of sea creatures and kelp/algae/seaweed. So I was looking into other foods and seasonings (besides salt) there could be and came across the sugar under the sea meadows. I wanted to know if there was a way for them to harvest the sugar there to add onto their cuisine.

Their technology is mostly with primitive materials at this stage. They make due with what they can with: seaweed/kelp, shells, bones, rocks, driftwood, sea glass, things salvaged from shipwrecks, reefs, coral, and whatever other things they can get in the ocean. They have also of course achieved very sophisticated free-range farms for their “vegetation”, numerous methods of fishing/hunting, and rearing of numerous sea creatures from krill to small whales. Some races advanced to where they could make primitive paddleboats as expensive as they may be.

With this info, how can they harvest sugar under the sea meadows with what they currently have?

If it helps, I’m looking at the sea grass meadows surrounding Australia in particular, but feel free to use other examples if it improves an answer.

(got approval from the Sandbox this time)

  • $\begingroup$ "A team of scientists now reports that seagrasses release large amounts of sugar, largely in the form of sucrose, into their soils -- worldwide more than 1 million tons of sucrose": For reference, the global production of sugar is about 170 million tonnes per year. $\endgroup$
    – AlexP
    May 22, 2023 at 21:29
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    $\begingroup$ @AlexP Still way more than I thought could be made under the sea…which was 0. PS HOLY CRUD that’s a lot of sugar we consume. $\endgroup$ May 22, 2023 at 21:32
  • $\begingroup$ ... And those 170 million tonnes per year are actual-sugar sugar. High fructose corn syrup etc. are extra. $\endgroup$
    – AlexP
    May 22, 2023 at 21:33
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    $\begingroup$ This question answers itself. $\endgroup$
    – Nosajimiki
    May 24, 2023 at 15:37
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    $\begingroup$ I'd like to reopen this question as I've edited it to include more on-topic information on my question, such as the people and world this farming is taking place in, as well as the existing level of technology. $\endgroup$ Jul 3, 2023 at 20:47

4 Answers 4


It might be better to instead breed the seagrass so that it retains more sugar in the rhizomes, then harvest and process these like sugarbeet.

  • $\begingroup$ Okay that’s a start! I was so focused on the sand and water around the roots I completely missed the roots themselves. $\endgroup$ May 24, 2023 at 23:04

I have an idea as to how this sea grass could be harvested, but I think it would be much easier to just use sugar cane. It is already a very water intensive crop, but unfortunately cannot grow in salt water. Your merfolk can squeeze the sugar cane, perhaps into a sponge, then put this into a clam shell, and bind it tightly with seaweed. This will slow the loss of the liquid to a minimum. If you want just crystal sugar, you would have to boil it. A sun cooker would be a monumental project, and likely would not suffice, and fire cannot be used for obvious reasons.

The seagrass' roots contain more pure sugar then the soil. It will be easier to harvest from there. Crush the roots into a powder, preferably in a area without water. Then seal it however you can, perhaps the clam wrapped in seaweed method might work. Add the powder as a sweetener, unfortunately you cannot purify it further without heat. Maybe if you have access to underwater vents you could place the container over it, heating the interior, but I doubt that will work.

Supposedly the mucus of a honeycomb moray eel is sweet, but this is undocumented. (This is entirely a theory based on fish behavior, supposedly the sweet taste lures the fish.)

Some mangrove trees produce edible fruit. These can be turned into sweeteners.

The sugar cane juices can be applied to food like a syrup, and the seagrass root powder, like a powder. Preferably you would place what you wanted sweetened in a container, like a barrel, then add in the sweetener, seal the barrel, then shake it or roll it. Hopefully the powder and/or 'syrup' will stick to your food, like a glaze.

  • $\begingroup$ While this is heavily dependent on the quality of the container used, you could technically pasteurize your seagrass with hydrothermal vents : Those apparently goes up from 60°C to 300°C, sometimes more in short bursts. That's normally enough to start killing bacterias, 'specially in a thermally conductive environment like water. We have yet to know whether the seagrass would be edible after such endeavor, and the short temperature bursts could make it harder, but... [...] $\endgroup$ Sep 22, 2023 at 12:11
  • $\begingroup$ [...] But that makes the world even more interesting : Batches of sugar clams will vary in quality and safety, so you will now need dedicated sugar artisans. This also leads to various types of buyers (rich and poor...), counterfeiting, etc... $\endgroup$ Sep 22, 2023 at 12:11
  • $\begingroup$ I've awarded you the bounty since it is the most in-depth answer. Yes, of two answers, but psshtt don't tell anyone ^^'! Moreover, this answer focuses on the means of gathering and storing some sort of sugar, which can be a very important yet easy oversight. Most importantly, this answers at a fundamental level : It will serve as the basis of all that critical stuff that depends on it (breeding species, automation, best locations...) $\endgroup$ Sep 25, 2023 at 12:13
  • $\begingroup$ @Tortliena I really like this insight! The hydrothermal vents idea may actually jibe well with some other worldbuilding concepts I have. $\endgroup$ Nov 23, 2023 at 3:58
  • $\begingroup$ I didn't understand the process. Do you say that the seagrass secrete the sugar into the soil? They would rather store it as food reserve inside the rhizome. Living organisms (plants included) keep the sea salt out, so it is easy to harvest the seagrass rhizomes, and process them on a floating raft: Squeeze the rhizome juice and let it evaporate, to collect the precipitating sugar. $\endgroup$ Nov 23, 2023 at 15:21

The plants have been genetically engineered to store the sugar in the roots, and the roots have been engineered to work as a network to supply hungry "neighbours". Tapping the root network on site allows to extract the juice without killing the fields in a sustainable way.

Then a third genom was crafted on, resulting in cellulose coveredd sugar bladders forming on the roots. Given enough growth, the sugarbladders stem rips off and the whole thing drifts to the water surface.

Thus some droneboats just drive along, collecting floating sugar-bags. It was all good, till that faithfull day, a narco-sub crashed into a cliff, releasing a myriad of columbian snow packages.

People could not get enough of the real ocean grown "coca cola".


Harvest the seagrass, take it to a dry place (like a floating home or the shore). Let the seagrass dry, grind it to a powder, let it dry further. You will have a powder that has some quantities of sugar and salt in it.

A sea-dwelling species should not need to care about the high salt content in that powder. But if you wish to trade some of that sea-sugar with some hypertension-prone species, or increase the incidence of diabetes among your own people, you can refine that sugar further.

Get some booze - the stronger the stuff, the better. Aim for something that you could use to sterilize surgical instruments. You see, salt is not much soluble in alcohol, but sugar is. So you throw your powder into the booze, and most of the salt (both sea salt and lots of impurities) should settle in the bottom. Then you can transfer the liquid phase to another vessel. Drink some for your trouble and let the rest evaporate. You will end up with a very sweet powder that is mostly sugar.

  • $\begingroup$ That is extremely creative, like wow. Would there be the added taste of alcohol to the sugar? Like how beer-battered shrimp might still have the taste of beer, but the alcohol burned away. $\endgroup$ Nov 28, 2023 at 2:11
  • $\begingroup$ @Thunderhammer there is only one way to know. Someone should actually try this for real! $\endgroup$ Nov 28, 2023 at 4:22
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    $\begingroup$ FOR SCIENCE!!!! $\endgroup$ Nov 28, 2023 at 5:51

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