eli5: do nutrients from a whale fall remain on the seafloor forever?

Submitted by weakherofan t3_10pr2hd in explainlikeimfive

Hello, I'm not sure if this is biology or chemistry or oceanography or what. I'm not much of a science person. I'm also going to preface this by saying i have anxiety and it's causing a dumb anxiety attack for me so sorry if this doesn'take sense.

As far as i can tell, oceans and land like to work in cycles, to deliver the necessary building blocks of life. water cycles and the migrations of animals mean that nutrients cycle between the two. The carbon, nitrogen, phosphate and so on in my body will decompose into the soil, and then rain will carry it into a river. It will be swept into the sea. Somehow, it will end up in a salmon eventually and be carried up the rivers back into the land. I'm not super technical, but basically the food chain is actually a cycle but on a larger scale. it's poetic and comforting that things cycle like that.

But when a whale falls all the way to the bottom of the ocean and is eaten by deep sea animals... I don't know how the cycle moves those nutrients back up onto the surface and then land. As far as i can tell, those animals don't interact much with the middle of the water Column so it's not super common for them to then be eaten by other animals from the coastal areas. Maybe sperm whales versus squid? How do the nutrients consumed by the hagfish return to the cycle and then end up in like. A tree. A cow. Me? I'm missing the links in the food chain and i can't find it on the internet.

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nmxt t1_j6m35dw wrote

Those nutrients eventually get decomposed down to carbon dioxide and other simple compounds, which enter the oceanic circulation and get back up eventually, although it might take hundreds of years for a single atom of carbon to enter the atmosphere again. Sometimes the nutrients get buried by sediment before they can be completely decomposed, and then they become part of the tectonic plate and only get recycled in volcanoes (or not at all).

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weakherofan OP t1_j6lxpgb wrote

Sorry. To add to this, i was under the impression that fish can't move from the deepest parts of the ocean floor up the water column very far, because the pressure is to different and they'll be unable to hold their shape and therefore survive.

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CallFromMargin t1_j6lz27y wrote

Generally when whale dies it's corps support whole ecosystems, and can take years to decompose. First, large scavengers will feed on it, and those will be on or near the surface, then small bits and pieces will start falling down and support deep ocean ecologies, but we don't truly understand those. Depending on how deep you go, they will feed anything from fish to microbes, and entire deep ocean ecologies rely on decomposing animal bits falling to ocean floor.

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weakherofan OP t1_j6lz9ki wrote

Ok but those fish now have the nutrients. I get that. But how do those nutrients then end up back on the surface. Or will all nutrients remain in the deep sea once they end up there?

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valeyard89 t1_j6maim7 wrote

A fish might eat another fish, then get caught by a fishing boat. But negligible. More nutrients are constantly being created at the surface (eg plankton) than any number of whalefalls.

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oblivious_fireball t1_j6m2iwk wrote

ocean currents or animals that migrate to shallower water at night will redeliver nutrients. over time other nutrients and minerals get reabsorbed with tectonics back into the earth and erupt out of volcanoes

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