This can be blown in from the Sahara occasionally. The whale faeces float, whales eat at depth but due to the high pressure of the deep ocean they can only defaecate at the surface.
If they’re in an eddy and grouped as a pod the nutrients are concentrated in an area the plankton can then use the iron, and the krill which live for six years or so feed on it.
The idea being to seed the oceans with simulated whale faeces this should jump start the plankton and ideally the krill giving the whales an opportunity to feed should their numbers expand, a trial in the Arabian ocean is planned to start.
Currently iron levels are only sufficient near the coasts, the hope being that all far more of the oceans could start to support life instead of being deserts.
This Inside Science podcast has a good bit about it all:
https://www.bbc.co.uk/programmes/m00114n7
Just thinking about it, this sounds slightly like Dune. The whales being the sand worm of the oceans, reprocessing krill into plankton food which is thought to have a huge effect in sequestering carbon.
I wonder how much of this recycled krill nutrient is removed by humans in the form of ambergris, to meet the requirements of wealthy women.
[Edit] Apparently it is excreted, perhaps by pooping; but it isn't quite poop.
A forest with all the seedlings eaten out struggles to recover from the death of mature trees, which is normally an opportunity for an explosion of growth - the decaying trunk restores nutrients to the soil, the sunlight streaming through gives the seedlings an opportunity to grow as fast as they can.
So continual overpopulation ultimately leads to the head of deer a given area of forest can support dropping significantly. Predation, whether by wolves or humans, can reduce the deer population to the extent that allows the forest to recover, which in turns leads to the forest being able to sustain larger populations of deer.
For example, maybe krill do a poor job recovering nutrients from dead krill, while they do great job of it with whale waste. In this case, whales would keep the overall amount of nutrients available to krill high while also consuming them.
Who knows what's actually going on here, but it's really not difficult for these sorts of highly interrelated systems to end up with counterintuitive dynamics.
For instance: Krill need chemical X when young but create it when older in large quantities. Wales poop out X then. Or wales create X, while krill do not.
Another possibility is recycling. Suppose the rate of iron addition via dust seeding is A tons per day, the rate of iron lost when a krill dies of old age is 60% and the rate of iron lost when a krill is eaten by a whale is only 30%. If the average age of krill dropped by say 20% then the biomass of krill should significantly increase.
Phytoplankton convert sunlight and dissolved CO2 into biomass, krill eat phytoplankton, baleen whales eat krill. So the role of the whale poop is fertilisation. https://en.wikipedia.org/wiki/Iron_fertilization
(i am not a krill expert)
It’s like fertilizing soil with the dead… it could in theory support ever growing populations.
If we arrange more material into phytoplankton, that would seem to leave less material available to be krill.
> It’s like fertilizing soil with the dead… it could in theory support ever growing populations.
But this cannot work in theory. A population cannot grow if its only nutrient input comes from dead members.
That’s the point your missing. The nutrient input is coming first from the sunlight. The phytoplankton nutrient for the krill is limited by the available iron.
> Sunlight is a source of power; by assuming unlimited sunlight input we can rearrange as much material as we want, but we can't add or subtract any.
Photosynthesis creates nutrients at the base of all food webs (except deep sea geothermal vents) It’s able to allow plants to take carbon dioxide out of the air and fix it as a source of chemical energy. The sunlights radiative energy then is converted to chemical energy which then acts as a nutrient for other living things. The nutrient addition is literally arriving out of thin air. (C02 into sugars)
However, organisms and in this case the phytoplankton doing that photosynthesis, are limited by specific nutrients, otherwise known as regulating factors. [1] In this case sunlight, carbon dioxide, etc would allow for massive growth of phytoplankton in the ocean. However, even given unlimited amounts of those, the phytoplankton will hit a growth wall when it runs out of iron.
That iron, in this case, was locked up in vast amounts of krill. Krill from my knowledge can live up to 10 years. So that means that a balance will be reached between the krill and phytoplankton in terms of population densities and where that limiting nutrient of iron is stored.
Whales change that limiting nutrient balance. By eating the krill and releasing the iron, the phytoplankton is able to increase its growth rate.
Krill then, feeding on the phytoplankton blooms will reproduce quicker. Iron that was once locked up in krill for 10 years allows faster reproduction rates of new krill.
The energy input that allows both populations to grow in this scenario is the sunlight. Again, the iron is only a limiting factor. The limiting factor is not 100% of the energy input. The iron is not “used up” meaning it’s availability to allow increased photosynthesis remains.
The end result is that a significantly larger proportion of sunlight is captured and converted to living matter which allows a net positive gain in both populations. This is possible because the regulating factor for increased photosynthesis is maintained in the ocean at higher levels with whales.
1. https://en.wikipedia.org/wiki/Limiting_factor#Ecology
https://sciencing.com/effect-limiting-nutrient-ecosystem-517...
But a limiting factor is the trace minerals they need to do so - iron is key to photosynthesis. In fact, people have proposed deliberately seeding the ocean with iron to stimulate phytoplankton blooms to fix carbon dioxide... not sure I agree with that, given the risks of harmful algal blooms.
The krill eat the plankton, the whales eat the krill, the whale poop contains iron that the phytoplankton need, it's the great circle of life.
But it can only be in one thing at a time. More algae can't lead to more krill if the existence of the larger krill population precludes the existence of the larger algae population.
Suppose I told you that by draining the iron from a bunch of humans we could promote the growth of iron-bearing plants that would feed a bunch of new humans. How much surplus iron could we drain from a living human? How many new humans could sustain themselves on that amount of iron?
Give it a long time for coevolution to take place, then have something suddenly happen to the mosquito population that was extracting the iron from the people, and we could see the same dynamic.
There are a couple of ways this could work.
The human population might have access to a source of iron which is not available to the plants. In this case, we can model the system as iron going from a mine somewhere (say) to the plant population, mediated by human remains. The iron isn't being drawn from the human population.
Or, this human subspecies might store a lot more iron than it actually needs to survive. Maybe they grow their own metallic armor or something. In this case, the remains of one human contain enough iron to support several other humans, so returning human remains to the soil in order to grow more plants could cause in increase in the human population, though the new humans would have impaired armor or whatever.
The issue I see with the iron/algae/krill model is that it's explicit that the additional iron for the algae is coming out of the krill. So we have two questions:
(1) Can krill get their iron through some other means than eating it?
(2) Do krill sequester more iron than they need to survive?
I'm assuming that krill obtain their iron through their diet. So unless an adult krill sequesters more iron than it needs, it doesn't really matter how much algae the recycled iron can produce -- less iron in the krill population will necessarily mean a smaller krill population. If the krill population isn't limited by iron, it may be happy to grow to accommodate the new larger supply of algae. But in order to do that, it will need to keep a certain amount of iron. If that iron has to come out of the algae the new krill supposedly eat, then how much larger is the new supply of algae really? Once the krill population gets back up to its original size, all of the "additional" iron is gone.
Putting this another way, if we think that algae are limited by the availability of iron, and we also think that krill are limited by the availability of algae, then we aren't saying that krill are not limited by the availability of iron. They definitely are! But that limitation goes through the algae they depend on.
Just some quick Googling found this:
"Other types of whales, such as sperm whales, migrate to waters much deeper than the euphotic zone and they can scavenge iron from below and then return to the surface layer to defecate."¹
¹: https://theconversation.com/bottoms-up-how-whale-poop-helps-...
Not the main causes of course, I believe it is mine and fertilizer runoff which are the current leaders.
When krill die due to old age, they might sink to the bottom and be buried in sediments, so the elements stored in their bodies will exit the cycle, causing reduced biomass in the cycle, and this loss will not be completely compensated by what river water brings from the erosion of the continents.
A system that uses either more efficiently could result in a net increase in biomass, even if the system is “processing” more krill per unit time while doing so.
Whales eat squids.
And ships are made of iron.
Humans are probably putting more iron in the sea than whales do.
Rusty ships are avoided, some of the iron is molecularly bonded to other metals and minerals, and rust from ships will sink immediately, and isn't really very bio available anyway. Rust flakes and particles are kinda difficult (and large) for crustaceans to rend and digest.
Irony whale poop has buoyancy, and the iron is bio available.
And squid eat...
The plural of "squid" is "squid", as the plural of "sheep" is "sheep".
Perhaps "squids" refers to multiple superconducting quantum interference devices.
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