Could a jellyfish be bio-engineered to convert salt water into fresh water?

Question

For my future world, I've decided that coastal cities need fresh water and there isn't enough of it to go around.

I don't know how jellyfish work. Is it feasible or completely impossible for scientists to bio-engineer giant jellyfish to convert salt water into fresh water? Do they store water in their bodies, or are they just made of water?

I would imagine that the jellyfish would convert the salt water into fresh water and it would be stored in its body for humans to harvest later. Could that work or do jellyfish not absorb water into their bodies and can't do this?

Answer 1

No. Jellyfish are osmoconformers

Osmoconformers are marine organisms that maintain an internal environment that is osmotic to their external environment.[1] This means that the osmotic pressure, or osmolarity, of the organism’s cells is equal to the osmotic pressure of their surrounding environment.... Most osmoconformers are marine invertebrates such as echinoderms (such as starfish), mussels, marine crabs, lobsters, jellyfish, ascidians (sea squirts - primitive chordates), and scallops.

Vertebrates maintain an internal environment that is slightly hypoosmolar - less salty - than seawater. Blood is not as salty as the ocean. I have read that the salinity of blood is the same as the salinity of the ocean in the ancient period when our ancestors evolved closed systems.

All that said I like the idea of giant bioengineered jellyfish. I can definitely imagine an anime with loads of giant jellyfish all around. Or was that Ponyo?

Answer 2

Is it possible? yes but...

There are biological constructs capable of filtering salt. Could a creature theoretically convert salt water to freshwater, yes but the big question is what does it do with the salt or water?

The law of conservation of matter still applies.

I would think this creature could be kind of like a stromatellite building a big salt rock on its inside. Though as soon as it punctured it would be chaos.

Maybe it could store the Na and Cl ions as a means of metabolic energy.

It would need energy to do this.

Could it look like a jellyfish? Maybe, depending on what it does with the salt and how it acquires energy will greatly affect its appearance.

If it photosynthesizes, it wont be that clear color. If it makes a big salt rock it likely wont float or if it does it sure wont look like a jellyfish.

Im also not convinced it would be capable of completely desalinizing water but im not sure it couldn't either.

But, on the salt rock train, I could see a thermally powered anemone concept that looks like a jellyfish stuck on the floor.

There is also the inverse of storing salt and instead store the water. In this case the jellyfish would inevitably float and be stuck on the surface which is useful because it makes harvesting easier. They would be like organically grown pre-filled water bottles. But no amount of tinkering could overcome the buoyancy problem because the stored water would be less dense than the ever increasing saline water, that is in addition to retaining the jellyfish structural appearance.

Answer 3

Sorta maybe.

Jellyfish don't do much, but some do generate pressure to swim. If you put a valved membrane across the ring muscle reverse osmosis could give you fresh water.

However fresh water is bad for jellyfish, and moving it from the mouth to somewhere you want it is work. So you need to give the the jelly some non-jelly plating, and a second exit for the water to be pushed into. With those changes you are halfway to a squid.

Really though I'm just using it as a living pump, so most creatures would work fine. Filter feeders like mollusks might be a better choice since they already are capable of pumping, filtering, surviving hostile environments and don't have a lot of unnecessary propulsion systems. And as a bonus make pearls and shells.

Answer 4

Seawater fishes do have the same problem.

Their skin (and scales) aren't exactly watertight - meaning, next to swallowing up seawater with their food they take up seawater through their skin as well which would raise the salinity of their blood and tissue.

So, to counter that their kidneys do actively transport the excess salt into their urine to be expelled whch gives their urine a higher concentration of dissolved salt than the surrounding seawater.

Meaning, a natural desalination mechanism already exists, though only in higher order organisms which need to rely on more complex mechanisms to expel waste material, but it could be feasible to engineer a bladder-like structure with a membrane with active transport to move a highly salinated solution out of it, thus reducing the salinity inside the bladder. Or, on the other way round, these organisms could be engineered to "pull out" the salt out of the solution they swim in and sequester it in their bodies, much like kidney stones growing.

Answer 5

Well, not in the way you're probably thinking of. Jellyfish aren't filters, and they don't extract salt from the ocean as they pass through it- so you can't use them directly to extract the salt from ocean water. As Will points out, they're osmoconformers and could care less about the salinity of the water.

However, I can think of a few ways to use jellyfish as part of the water purification process.

1) Use them for transport

This idea requires a bit of technology on the scientist's part, but well within reality. The key tech here is a semipermeable membrane that allows water to pass through, but not salts. These are commonly used in modern science and are part of the reverse osmosis desalination process. With a semipermeable membrane, all that's required is a pressure differential.

Jellyfish are bad at a lot of things, but moving vertically in the water column is not one of them. Some jellies, such as the beautiful and massive Lion's Mane jellyfish undergo daily migrations between the surface and the depths, known as diel vertical migration. If properly trained, I can easily imagine our massive Lion's Mane jellies making daily trips to the seafloor with a semipermeably sealed container on their bells, which would fill with fresh water, rejecting salts, as the jellies sink to the seafloor. Each night, they would return to the surface with containers filled with fresh water.

2) Engineer them as substrates

Some jellyfish would be excellent candidates for the harvesting of biological, semipermeable membranes. In particular, the Portuguese man o' war, while not a true jellyfish, has a large float made of a single cell. This float could be repurposed or engineered by scientists to produce biological semi-permeable membranes that could be harvested for the larger desalination plants, solving the problem of constant, expensive filter replacement. Additionally, semi-permeable membranes made from jellyfish would likely be less vulnerable to dissolved organic carbon, which is actively problematic for current systems.

Answer 6

This is really not what you asked, but your question got me thinking. In the real world, the favorite solution for coastal cities without enough water is to channel it from other areas. When that's impossible, the solution is physical desalinization in a process called reverse osmosis. You're looking at biological desalinization.

Jellyfish are a bad choice. As Will said, they maintain the same salinity as the water around them. Changing this would involve so many changes to their physiology that the result would not be jellyfish. They'd need a circulation system like you see in fish to isolate the salt from the surrounding water.

Usually, single celled organisms will be easier to breed into a specific task like this than complex organisms like jellyfish. So what you can do is breed bacteria that maintain internal salt content higher than the water around them. I'm handwaving how you would do this, but a microbiologist might have some ideas. Then you filter the salty bacteria out of the water, leaving behind less salty water, or even fresh water if the bacteria are efficient enough.

If you really want jellyfish, you could make them host the engineered bacteria. But at that point, you'll have a huge drop in efficiency because instead of just feeding bacteria, you have to feed the jellyfish plus the bacteria, and will probably have much less bacteria.

Answer 7

Since you're free to explain this any (plausible) way you want, you could have bio-engineered jellyfish that are captive. They are tethered offshore and are connected to a pipe system that continually transports the fresh water back to shore. The jellyfish are filter-feeders, taking-in nutrients and sea-water, excreting digestive waste and salt back into the ocean, and having the fresh water tapped from their bodies in some way.

You could even make them "solar powered" like a lichen by having a captive plant contained within the body of the jellyfish to provide extra energy. Since the jelly fish have clear bodies, they could be tethered right at the water surface and sunlight will easily penetrate within the body to provide the power.

Answer 8

At the very least those jellyfish will need to resist the osmotic pressure, so they will need a hard carapace and / or thick rubber-like skin able to withstand that pressure. So the answer is "no", unless you're ready to call such creatures jellyfish.

I suppose it would be easier to bio-engineer a regular fish into a slow-moving bloated organism consisting primarily of water with low salinity. Still, it would never achieve the body water content that jellyfish have.

Answer 9

As someone said, what do you do with the salt? It would eventually make the ocean too salty as you remove the fresh water. Better invent a machine to separate H20 and use sodium and chloride, both very unstable elements to generate the heat(energy) to do it. BTW fresh water is available aplenty in the colder waters of the artic within the old ice, and in deep water. Since hot salt water floats to the top, perhaps you can find cold fresh water deep down in pits on the ocean floor. Or perhaps you can make a plant that drinks salt water, survives and yet produces a freshwater fruit like Watermelon.