Page updated March 10th, 2019.
So WHY this should be done.
First, we have to find new food resources: For the soon to be 9 billions individuals, our food production needs to increase drastically. It is easily understandable that broad spare areas and quality water in quantity is the least we will need. On the contrary, as desertification and urbanization progresses, available arable lands shrink dramatically. Remaining forests and wild lands are either highly coveted or already acquired. Fresh water is hit by scarcity or pollution, and most of the coastal seas are not even free for new exploitations anymore.
So where are there still enough space and water? On high seas !
Secondly, we need to keep the oceans resources (and us) healthy: Oceans fish resources are overexploited. For several years now, despite the fisheries' technical efforts, going always further and deeper, the wild capture production stagnates. The global production does not regress, only thanks to aquaculture which grows rapidly, and tends to exceed the capture production.
(Source: FAO, The state of world fisheries and aquaculture 2014)
The inland farming of herbivorous fish (carps, tilapias) is still able to increase as long as appropriate locations can be found on land, but the marine farming of carnivorous fish (salmon, bass, cobia) is in a predictable dead end. It bites its own tail, as wild forage fish is necessary for feeding, and is unfortunately lacking more and more. Therefore, the fish farming industry tries to reduce and substitute its contribution in their feed. The ongoing attempts to feed farmed carnivorous marine fish with terrestrial agricultural resources, instead of fish meal and fish oil, may work technically, but make us actually lose all the benefits of a healthy fish, and so, healthy food for us.
Indeed, marine proteins are healthy because, set apart their good amino-acid profile, vitamins, minerals and trace elements, they present high levels of long chain omega 3 polyunsaturated fatty acids (PUFA), well known to develop our brain and protect our heart and eyesight. Fishes, as all aquatic organisms, need a very large amount of omega 3 in their diet, as these are the fundamental constituent of all their cell membranes. These essential PUFA are nearly exclusively produced by phytoplankton, the first marine trophic level, which is assimilated by zooplankton, which is assimilated by forage fish, among others. Without an appropriate amount of PUFA, fishes are much more sensitive to stress, undergo diseases, and have more difficulties to bear with parasites like sea lice. In today's most aquaculture plants, in order to grow properly despite those issues, the feed have to be complemented with antibiotics and the water treated with pesticides, which are both ultimately ingested by us. With a long chain omega 3 rich diet, farmed fishes are much more healthy for themselves of course, but also for us. For our part, as all terrestrial organisms, only some of our cell membranes are constituted from PUFA. Nevertheless, this bunch of cells constitutes our eyes and our brain. That is why, we also need to ingest PUFA to grow and keep healthy. It thus becomes quite critical to us to preserve farmed fish as a good PUFA long chain omega 3 source.
(Source: Philip Chou/SeaWeb/Marine Photobank)
My ambition is to develop a colossal and healthy animal protein source in the high sea desert, more than enough to provide long chain omega 3 rich feed to our noble fish farms around the world. Thus, fish farming will not be deadlocked any longer and would be able to provide a healthy food for us. Further, forage fish will remain in sea to nourish penguins, seals, dolphins, whales, sharks, seabirds... and wild fish from upper trophic levels we also want to catch and to eat. Rather than just looking down on how fisheries and aquaculture are managed nowadays, I suggest the whole process to be re-thought in a pragmatic way. The main thread of my reflection is based upon an implacable logic:
"The better we aquaculture, the less we fish, and let the oceans live"
But HOW are we going to achieve all that ?
Weather conditions are the first issue encountered when operating any infrastructure on high seas. So let us first choose the only ocean not to be prone to cyclones, typhoons or other hurricanes, South Atlantic. Besides, it is the poorest ocean both in terms of fisheries and maritime traffic, so we should find an unoccupied and safe place there.
(Source: NASA Earth Observatory)
The lack of mineral nutrients for phytoplankton is the second issue on high seas in general, and in South Atlantic in particular. Except in some eastern areas, where constant winds from land cause upwelling, algae bloom and related important fish production, it is a real desert out there. Anyhow, we have to content us with the desert areas, because the naturally rich ones along the african coast are already exploited and occupied. Farther west, the nutrients present in the photic zone - above a 100 meters depth where light comes in - are quickly completely consumed by phytoplankton's photosynthetic activity. In these conditions, the phytoplankton cannot multiply enough to feed many zooplancton. That is why the high seas are biologocal deserts. No existing wind is strong enough here to mix the layers, and the mineral nutrients are not massively renewed from the deeper layers, where they stay present in quantity.
(Source: SeaWifs Project)
The challenge now is to bring the existing nutrients from the depth and the light from above together. Doing the math, there are only two possibilities, bring light down or bring nutrients up. Let us have a look at both.
Bring light down:
Due to the aggressiveness of ultraviolet radiation from the sun, and to the constant adaptation of the naturally sinking algae, the optimal wavelength for its photosynthetic activity is within the blue range, the one that have the highest water penetration coefficient. Luckily, thanks to today’s LED technology, we are able to produce just the needed blue light with very few energy. Furthermore LED can easily be deployed in high pressure environments, because, unlike light bulbs, they are not hollow and cannot implode. But, even if we manage to illuminate properly a portion of the dark aphotic zone - below 100 meters depth - with strings of blue LED, we still need to survey, handle and fix a production process in these depths… This is feasible, but too constraining.
Bring nutrients up:
Unfortunately, nutrients are diluted in great amounts of water, far too much to be pumped up with external energy and create an artificial upwelling. It would not be economically viable to spend so much energy. So can we bring up colossal amounts of nutrient-rich deep-sea water without energy? Yes we can :
Antarctic Intermediate Water (AAIW) is a nutrient rich, and low salinity water body, which characteristics are due, among other factors, to the mixture of seawater with mineral rich and fresh meltwater from the southern ice cap. These are the waters, where the antarctic life explosion takes place every summer. AAIW flows slowly northerly in every oceans. In the South Atlantic, it meets warmer and saltier sub-Antarctic water at the convergence zone, 50°-60°S. There, it sinks to approximately 1000 meters (3280 feet) deep, gliding over cold, salty and very dense bottom water. A large part of it is flowing northeasterly to the South Atlantic Gyre, where it loses its characteristics by mixing. But a little part of it is flowing due north on Atlantic's west side, until crossing the Vitoria Trindade Chain east of Brazil. AAIW lays at this depth, and does not mix with the upper and under layers, even in this tropical region, where surface water becomes heavier, due to evaporation and induced saltiness increase. The sea stays stratified because the diffusion between the different water masses is too low, no storms are strong enough in this region to mix the layers, and no constant wind from land forms an upwelling.
(Source: Earth' Climate: Past and Future, written by William Ruddiman)
These conditions are ideal to set up a Perpetual Salt Fountain, an oceanographic curiosity, as first described by Henry Stommel et al. in 1956. If you put a vertical pipe between two layers, and pump it up until the pipe is full with the colder deep water, you can stop pumping and the up flow will last perpetually, without any other energy spending. This is due to the fact that the heat difference between the water masses is conducted through the pipe walls, but the salinity difference remains unchanged. This property has been recently validated on open sea by Shigenao Maruyama et al. from the Institute of Fluid Science, TOHOKU University. In our previous exemple, we have very salty and warm water above very little salted and colder water. The salinity having the largest influence on density, the salt fountain should be very strong. Here is our solution to bring nutrients up without energy spending.
(Source: Institute of Fluid Science, TOHOKU University)
Furthermore, AAIW, found today at 1000 meters depth in the tropical zone of South West Atlantic, was in contact with the atmosphere about 300 years ago, in other words, long before the Anthropocene, and the wide dissemination of its pollutants. Even with the inevitable transfers, caused for example by the daily vertical migrations of zooplankton, the concentration of anthropogenic pollutants in these waters should remain insignificant.
Another issue is to build a floating infrastructure with, at least, a 1000 meters deep anchorage, or with dynamic positioning. This is quite preposterous if you consider the scale of the area, and the production we are aiming to. Help is provided here by seamounts, and more specifically guyots with a flat top, extinct volcanoes rising up from the seafloor, sometimes almost to the surface. Such a guyot is perfectly suited to support an infrastructure on its top and pipes along its slopes. In addition, due to Taylor columns effects, seamounts have the particularity to let the isotherms rise a bit, and form a vortex that retains the surrounding waters. This phenomenon allows us to find AAIW at less deep level and, after being raised trough the Perpetual Salt Foutain pipes, to keep it a while above the seamount for exploitation.
A last issue is the needed energy supply so far away from the cost. Overlooking fossil fuels which have no more real future, let us have a look on renewable powers.
Solar energy: a large area of solar panels is too fragile in this environment.
Wind power: technically feasable, but no regular supply.
Wave power: too fragile and no regular supply.
Current power: needs a very strong current which is better to avoid.
Osmotic power: technically too complex.
Ocean thermal energy: too sophisticated and too costly.
What else ? Geothermal energy on high seas !
Why not, being located above an extinct volcanoe, rising up from the seafloor almost to the surface ?
And WHERE could it take place ?
I managed to found a suitable guyot in the Vitoria Trindade Chain, east of Brazil, the Davis Bank. It rises from 4000 meters on the sea floor to less than 50 meters depth (160 feet), and has a very large flat top, around 90000 hectares (222000 acres). In the tropical southwest Atlantic, it is the only known suitable seamount, which does not belong (yet) to a national Exclusive Economic Zone (EEZ).
But WHAT shall we produce there ?
The core of all production in the sea is phytoplankton, which multiplies rapidly, subject to presence of mineral nutrients and light. From there on, a short trophic relationship with an organism, which has a good conversion efficiency, would be the most effective and healthiest way to produce anything.
Sessile filter feeders like mussels are good candidates, because they belong to the second marine trophic level, don’t spend any energy to swim and cannot escape. The very short trophic relationship between primary production of phytoplankton and production of mussels assimilating it, combined with the very pure AAIW quality, are the unquestionable guarantee of the lowest level of anthropogenic pollutants at the end of the production process.
Mussel aquaculture has been practiced for centuries, even millennia, because it is rather an easy culture. They multiply profusely, attach themselves on any surface or created device, and feed on any organic matter they find. Several techniques are used nowadays. Using long lines is the most productive technique for mussel aquaculture, because it takes advantage of the volume in the water column, instead of a surface. However, this production method, intended for human consumption, is too expensive, and needs to be improved to fit aquaculture diet production. Several stage sorting and mussel cleaning can for instance be discarded, sparing a lot of time and money. The long lines themselves are too expensive in their actual form, and need also to be re-thought.
(Source: The MARICULT Research Programme)
Despite these observations, long lines mussel farming is by far the world’s most productive breeding method, with currently 150 tons, up to 300 tons, per hectare and per year. To put those figure into perspective, beef production is only around 0,340 ton per hectare per year, almost a thousand times less ! With mussels on long lines, we can reasonably forecast a production between 3 to 6 million tons of mussel flesh (75% is shell) in a square of 90.000 ha, like the flat top of Davis Bank is. This figure can also be compared to the 4,7 million tons of Peruvian anchovies caught in 2012, world’s largest fishery dedicated to the production of fishmeal and fishoil.
However, as a consequence of their relative easiness to be cultured, some aspects of mussels’ biology, like their most efficient diet, have not been sufficiently studied. We just know that mussels ingest preferably plankton and other organic particles from 5 to 15 microns. Diatoms, the main intake, provide DHA (good for our brain) and flagellates provide EPA (good for our heart), both important PUFA omega 3. The control of mussels’ diet, until now neglected, has all its importance here, especially if it is revealed to be adjustable.
Each mussel filters nearly 100-liter water a day. Retaining all the present particles, its food conversion factor can be very fluctuant, between 30 and 80%. That means mussel produce between 20 and 70% faeces (which pass through the digestive system), or pseudofaeces (which are immediatly rejected). These sink and pollute the surroundings, because the organic charge is too important for being degraded by aerobic bacteria during the fall, especially when the bottom is not very deep, what is mostly the case in mussel culture areas. Once the faeces are accumulated on bottom, anaerobic bacteria take place, with its inconveniences. That’s why knowledge about mussels’ most efficient diet has its importance. Especially if we are able to sway this food conversion factor and the nature of the metabolized substances, by using the appropriate phytoplankton mix to feed the mussels. In our case, these particular phytoplankton species can be injected in the rising nutrient-rich AAIW passing through the salt fountain pipes, to let them multiply on their way up, thanks to strings of blue LED inside the pipes. That’s a way to control mussels’ diet, in order to minimize faeces and maximize PUFA omega-3 production.
Now we have the framework. But it will not work as it is, because of the environmental footprint of such a huge mussel farm. To avoid contaminations, it still needs to be atomized between several places, or at least separated in some way, by macroalgae for example. Anyhow, it needs also to be associated with other cultures to become a self-sufficient biotope. This technique is called Integrated Multi Trophic Aquaculture (IMTA) where one species' wastes are recycled as feed for another.
(Source: Fisheries and Oceans Canada, drawn by Joyce Hui)
Mussel faeces cause pollution problems in most of today's monoculture areas. To avoid this, the soluble faeces can be assimilated by kelp or an other macroalgae, and the solid ones can be assimilated by scavengers on bottom like sea cucumbers. These will also strongly contribute to the project's viability, because of their value for Asiatic people, who appreciate them a lot as food and medecine.
You can read more with IMTA Research Laboratory of Dr. Thierry Chopin.
These conclusions of mine are written without references to all the sources I used, because I do not claim to have done a scientific work. My project is all the same a solid base to the challenges of fishfarming sustainability and oceans’ biological productivity preservation. As a pragmatic ecologist and amateur oceanologist, I think it has to be done.
Follow me on My vision.