Feasibility of an amoeba sea

Question

Humanity has discovered entire worlds filled with creatures that would question their understanding of biology, but one creature, if it can be called, has brought up many many questions.

Appearance and behavior

The amoeba sea is a massive colony of amoeba Like organisms that stretch across nearly 75% of its planets surface, which is why it’s called a amoeba sea. The surface is solid enough to walk on, but isn’t solid enough for heavy objects, or prolonged standing. the amoeba sea is purple in color and underneath it, one could see either slow moving or completely immobile dimly lit lights which are thought to be some form of bioluminescence. The sea seems to slowly pulsate, which scientists think is a result of the air, but there isn’t any proof to back it up.

When being walked on, the researchers noted that the surface starts to become a lot more more liquid like, and in one instance, a scientist had “fallen” through the surface, and was presumed to be dead. This suggests that the amoeba sea will weaken is surface, causing any living organism to fall through and presumably be digested. When a drone had been sent to go under the amoeba sea, it found thousands upon thousand of preserved yet dead bodies and small cave systems filled with the amoeba like organism, which suggests that either the organism is actively yet slowly corroding rock in search for food, or has grown and replaced an entire sea.

extra facts

Recently, it has been seen that the local wildlife are safely capable of eating it, which means that the colony of amoeba like organisms might not feel pain, or just don’t react and is filled with enough water and nutrients to keep an animal fed for a few hours or days.

what environmental pressures would lead to a amoeba sea, and what parts of it are and aren’t feasible?

Answer 1

You're looking for photosynthetic slime molds on a primordial world.

The colonies need to be smaller.

The most glaring issue with this colony is its sheer size. Even alien amoebas need to eat - but if they take up 75% of the planet's surface, chances are they won't leave much room for prey, or nutrients, or much of anything. Even though many colony-forming eukaryotes and tons of bacteria live in our oceans, they haven't physically filled it because there is far, far too little food in the ecosystem. I can't give you a quote for how much of the ocean can be covered in this organism, but I highly doubt it exceeds 10%. If you're looking for a good place to put colonies, consider placing them near the coasts, where most sea life is on Earth.

The ocean probably can't be physically solid.

Solid structures atop a constantly moving sea won't last long. They also don't make much sense for undifferentiated, unspecialized colonies of microorganisms that need to eat. In a thick amoeba mat, how do the ones in the center get any food?

I could see some structures forming in a manner similar to slime molds (which are related to Earth amoebas!). You could create some vein-like tissues and organs to distribute nutrients, or to communicate about threats. However, nothing too thick would be able to hold itself together. This also rules out digestion.

Purple coloration can be explained by photosynthesis.

A colony (or group of colonies) this large definitely can't eat other organisms to get nutrients; what else could possibly be numerous enough to supply food? Instead, your colonies will make their own food from sunlight.

Early photosynthesizers on Earth used retinal, a purple pigment less efficient than the green chlorophyll we know and love. This is ideal for your world.

Your world is probably very young.

One hypothesis states that since chlorophyll is more efficient, the once-dominant retinal became far less prominent over time. Retinal may be one of the many pigments for photosynthesis that early life forms try out across the universe before reaching peak efficiency for their (sun-like) host stars. Inefficient purple pigment makes the most sense on a young world.

A young world is also consistent with the absolute dominance of your amoebas over the environment. They are likely among the first producers to evolve, so they have little competition and virtually zero macroscopic predators. The one caveat here is that you can't really have land animals, and bioluminescence is unlikely.

Finally, a young world may also be consistent with the pristinely preserved bodies within the ocean. Decomposers may not yet be common - so dead scientists don't break down easily.