Aquaculture is not a new concept. Humanity has been farming the sea for over 6,000 years. The Classics of Fish Culture, by Fan Li, is the earliest written record of aquaculture from 475 BCE and, around 500 BCE, the Romans farmed oysters and fish in Mediterranean lagoons. Modern aquaculture is more scientific and intensive but it still barely scratches the ‘surface’ of the possible.
This article describes some possibilities for the future of sea farming.
The fish farming industry is worth $160 billion US; the seaweed industry is worth more than $8 billion US. Humanity’s exploitation of the ocean world is pretty much defined by extraction of protein (fish), minerals and energy, some vegetable matter (seaweed and sea grass) and for leisure. What humanity doesn’t do is responsibly farm the sea.
There have been attempts at creating subsea gardens with large bubbles tethered to the sea floor and an internal environment mimicking the surface characteristics. What has yet to be successfully achieved is farming crops that grow in subsea environments naturally. Here it is necessary to think of both above-seabed crops such as grasses and seaweed but also those crops that flourish below seabed level such as mycelia (root systems for fungi).
Scientists have identified around 1,400 types of mycelia that flourish in different ocean environments. Conservative estimates suggest that there are probably more than two million eukaryotic organisms still to be identified. Fungi, like animals, cannot make their own food but acquire their food by secreting enzymes that can break down tough molecules like lignin and, as is now being discovered, plastics, which allows it to absorb dissolved molecules, and convert them into glucose or other useful food components. Fungi do not photosynthesise. Farming subsea fungi in a sustainable fashion will require detailed planning.
The cropland area of world is roughly 5.4 billion square miles (14 billion square kilometres) excluding grazing land.
Ocean area, above 200m (sunlight zone) is approximately 9 billion square miles (23.3 billion square kilometres) but fungi thrive all the way down to abyssal depths, see below illustration.
Many of the seas around the world such as the North Sea, the Baltic Sea, East China Sea, Yellow Sea, even the South China Sea and, to a lesser extent the East Sea (Sea of Japan), the Sea of Okhotsk have large areas of seabed within the Sunlight Zone and, having been above sea level for many thousands of years, have fertile sea floors. Of course, for subsea farming, there will have to be severe restrictions on fishing, especially trawling.
One of the major problems will be the inability to erect enclosures which, on land, led to the agricultural revolution and the manifold increase on production that evolved. Sonic barriers might be possible but may be expensive to implement while hedging consisting of kelp or other seaweed would need some serious research.
Given the complexities involved, it would seem unlikely that a single private enterprise would be able to deal with this opportunity. Indeed it may be beyond the capabilities of a single nation and only the economic giants such as China, India, the USA or the EU might investigate this. Against which private equity looking for very long-term rewards might be more fierce in protecting the cleanliness and sanctity of their investment.
Little is known of the life cycle of subsea fungi but it would not be unreasonable to assume that organisms flourishing in the twilight zone and below are relatively slow growing. In the sunlight zone, however, some of the fastest growing plants such as kelp which can achieve growth of 2m per day which is twice that of the fastest growing land plant, bamboo.
The ocean is mercilessly exploited reaping fish and crustaceans without replacement, dumping garbage and polluting the waters with agricultural run-off. This has largely been a result of what is commonly-known as “The Tragedy of the Commons”. If nobody owns something, it can be exploited by everybody and the most ruthless and careless generally ruin the concept. With the institution of enclosures, then intruders and those damaging property could be sued and prosecuted under law. This is possible now but administrations barely use their prosecuting powers to enforce non-damage or pollution of inshore waters (or even freshwater streams). So, beside the benefit of any crops harvested in seabed agriculture, there would likely be additional benefits in cleaner, more sustainable oceans.
What crops might be grown? At the moment antibiotics, anti-cancer and anti-inflammatory are found in abundance in marine inverterbrates such as molluscs (shipworms), gastropods (sea snails), tunicates and ascidians (sea squirts and such), sponges, bryozoans (moss animals), octocorals, annelids (sea worms), echinoderms (starfish) and fish slime are being harvested or researched. Anti-tumour polysaccharide drugs can be extracted from the marine fungi leptosphaeria. A compound called seriniquinone from Serinicoccus, a rare genus of marine bacteria appears to selectively destroy melanoma cancer cells (in the laboratory).
All this makes sense since marine animals, plants, and microbes have had to evolve unique portfolios of chemicals to defend themselves and aid communication.
However, none of these are very suitable for seabed farming. Sea vegetables, such as kelp, salicornia (sea bean), dulse (red algae), nori and aonori (Japanese/Korean edible seaweed), irish moss (used as a thickening agent and as a dessert), sea purslane, arame, badderlocks (type of kelp), gusô or eucheuma, hijiki, kombu, sea grapes, sea lettuce, wakame and oarweed (both types of kelp), and spirulina are all possible crops. It would be almost impossible to believe that amongst the 2 million unidentified subsea mycelia, there are not thousands that are cultivable, nutritious and edible.
This is a very contentious issue. Humanity’s record of land management has, on the whole, been fairly successful allowing the human race to rapid grow its population beyond limits thought possible.
Whether this is ideal is also open to question. But this, in turn, has allowed greater understanding of systems and laws of nature and the amount of knowledge available on this planet should allow humanity to continue growing and spread either here or elsewhere.
Over the last few hundred years, however, the damage humanity has caused both to other species and the environment has become apparent for which humanity must hang its heads in shame.
While the future of our species is in question, growth or managed decline, humans must, at the least, secure the comfort and security of those living and still to come. One way of doing this is a sustainable, considerate exploitation of those subsea resources as yet underdeveloped.
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