Farming the sea.
The world seems to many to have reached its limits. There are so many of us and so few acres of land. If you’re an unskilled refugee so many doors are closed that you have to risk dangerous boats to sail to freedom. Religious minorities and political idealists can’t strike out into a new frontier to seek their liberty or fortune. There is one open frontier left to populate on this planet, the open oceans. If we can live at sea we can again live free. If we can farm the sea then we can live there. If someone can live in international waters it’s no longer a commons but someone’s back yard. Fish stocks and pollution would be much better managed. Others have done the work on housing, see the sea stead to the right, and others have designed the fish farms. Now for the vegetables.
Bubble ponds.
An air and fresh water filled floating inflatable greenhouse. Fresh water floats on sea water but has a strong ballasting effect. The bubble is rubberised plastic on the bottom clear on top with a zodiac edge. The same as most inflatable boats and life rafts. The inflatable torus around the edge has an integral pod that includes power, pressurisation, reverse osmosis desalination, crop monitoring, fertilisation and some harvesting equipment. This pond rides the waves in light seas and dives below them in heavy seas. There may be a rigid but segmented floor level with the lower edge of the torus. Essentially the whole thing is a robot jelly fish. It's not manned but has a hatch attached for access and automated harvesting.
Food crops grown in this bubble pond would include.
Aquatic plants are much easier to grow on such a flexable raft than other crops. Because they are buoyant and water tolerant, there is less work. We only need to fertilize and deal with salinity.
Spiralina, (the major crop) other algae's including biofuel algae crops. Spiralina is an algae that can be processed into high protein noodles, powdered protein filler or textured protein. If the protein and sugars are separated the sugar rich whey has many uses.
http://www.spirulinasource.com/earthfoodorigin2.html#production
http://en.wikipedia.org/wiki/Spirulina_%28dietary_supplement%29
http://www.daenvis.org/technology/Spirulina.htm
http://www.spirulina.com/
Water spinach Ipomoea aquatica, This is a major crop option after spiralina. This is a green vegetable with hollow stems and requires no soil. We need to check its properties to see if it can be made into a sweet sugars, bulk starch or a bulking agent for spiralina based foods.
http://en.wikipedia.org/wiki/Ipomoea_aquatica
Water caltrop or water chestnut: genus Trapa - T. natans and T. bicornis.  A major starch source. Note with the right nutrient mix in the water these grow with little mud, like floating hydroponic plants.
http://en.wikipedia.org/wiki/Water_caltrop
Water hyacinth.  Currently an inedible non food aquatic plant yet it could be chemically processed into starch, sugar and glucose or livestock feed. Also a useful biofuels feed stock and a very useful fertilizer.
http://en.wikipedia.org/wiki/Water_hyacinth
Duck weed. This small fast growing plant has been used for human food in the past but is rarely eaten today by humans. Pulped either Water hyacinth or Duck weed could feed fungi, bacteria cultures and yeasts.
http://en.wikipedia.org/wiki/Duckweed
Semiaquatic plants and raft pot plants.
Yams, Taro, Rice, wild rice, watercress, edible lilies require more mud. These can be grown if the bottom is semirigid with a quantity of mud in a rubber mesh mat. Wave action would stir the mud a little and disturb the plants but they could be bred to handle that.
Raft farming is a possibility with buoyant pot plants that can be tethered in the plastic pond with some room to flex and move about. Normal water tolerant garden crops are grown on the floats.  Nothing more than a meter high can use      this process but that leaves many crops: Mints, Peas, beans, vegetables, etc. In this case the "pond" might be narrower and higher so waves squeeze it rather than overtop it. See the links below and also the permaculture work on floating gardens.
http://crazyponds.com/floating_islands.html
http://edis.ifas.ufl.edu/pdffiles/HS/HS18400.pdf
low technology vesion on fresh water
Salt tolerant shore plants.
There are two new salt tolerant crops available called NyPa grain and Nypa forage; Distichlis palmeri and Distichlis spicata.  These are derived from nyipa which will grow on sea water but grows better with sweeter water. Thus they reduce the load on desalination. They do require soil though. Perhaps these will do for places on the sea stead where salt spray may reach.
http://en.wikipedia.org/wiki/Distichlis_palmeri 
There are also sea side succulents pig face and salt bush that are used as vegetables by Aboriginal Australians but neither tastes great without processing. Both are good fodder though.
Salt bush data
pigface
 Nypa palm is an interesting plant as it is a food and beverage source and a source of sugars. It's the only palm that grows in sea water. Added rigidity would be needed in the floating pond to grow this crop but it would be very useful. A big hole in the top of the bubble would be needed this is a tall crop. Its papery palm leaves can be woven into mats, thatch and basketry.  There is also considerable woody material produced. Plyboard could possibly be made. Paper pulp if its required could also be a possibility with this plant.
http://en.wikipedia.org/wiki/Nypa_fruticans
Marine Algae.
Sargasso weed and many seaweeds. The desalination would be reduced or eliminated. Some of the seaweeds could be grown on simple rafts but the addition of the bubble means you control fertilisation and pest fish and crustaceans. The bubble means you are only fertilising the crop you want not the whole ocean. I would not want to introduce the Sargasso weed algae into the Pacific; we do not know what the consequences would be. Only an Atlantic sea farmer could farm this plant. Likewise the Pacific species: giant kelp and Japanese algae need to be kept out of the Atlantic. There are enough species to go round.
The idea is that this fresh water cropping system floats on the sea and flexes with the waves. Its a near term technology and growing crops on foam floats on dams and ponds does work. All the plastics of the "ponds" would be designed to be regularly recycled at little additional cost. The first challenge is to find a balance between rigidity and flexibility so the "plastic ponds" survive in unprotected seas.

Each pond has a large storage volume of fresh water that doubles as ballast.  It moves with the seas waves becoming part of them rather than fighting the forces of the sea. The ballast also stops it blowing away with the first breeze or flipping over in the first gale.
There is a chance that a good storm would destroy the crop but this happens to land crops anyway. These ponds increase the growing options of sea steaders greatly.


I am quite sure I have missed as many possible crops as I have named.
Greenhouse fluke boats.
These are floating greenhouse with integral wave power and propulsion. The plants are not effected as people are by the rocking action of the boat hull. The wave propulsion damps that as well. These vessels could be 2 to 4 meters in diameter and 12 to 40 meters long. About the size of a fishing boat or large life boat. They would be unmanned robot boats, GPS flocking software guidance, augmented with ladar and sonar, with some crop management automation and regular visits by the farmer.
While sea steads have to be above the waves and decoupled from them (see below); a fluke boat is a creature of the waves. It has a set of flukes attached to the keel. As the waves drive them up and down the fluke is shaped to resist part of this motion driving the craft forward. As a storm approaches the boats scatter out to sea to avoid collision and reefs. They return home to be linked back up after the storm. This is an old pacific island strategy to survive the worst storms and tsunamis.
http://pesn.com/2005/09/21/9600170_Wave_Propulsion/
A fluke boat may be attached to other floating systems: Bubble ponds, fish cages, the sea stead itself. Thus anchoring these systems to the sea bed may be avoided and these wave powered tugs simply tow every thing in one direction to counter the effects wind drift, wave drift and currents. As robot boats these vessels bring the crops to you for harvest so special harvesting systems are economically used. Collision avoidance is relatively easy using mast mounted ladar, sonar and GPS flocking software. Automated mooring systems and fenders would help. They are possible. Because these farms are vessels, there is a distinct possibility of farm racing becoming a pass time for our ocean farmers.
Another problem is solved by these boats mobility: A boat with bee hives on it can be moved around to pollinate the crops. Bees don’t like sea water so to pollinate a boat it needs to be moored to the bee boat and a large flexible duct set up to link the two. Bees can be trained to fly through a maze with markers on it. They are quite immune to claustrophobia often colonizing attics and tree hollows. A smoke generator activated in the boat being pollinated would cause the bees to return to the hive. A hardy bee keeper may live in the bee hive fluke boat several days in the week. The rocking motion would be the least of his challenges. Experiments to see if hives are effected by the rocking of a boat needs to be looked at however bee hives are often found in tall trees and the wind causes a considerable rocking action in tall trees.
Another feature of the green fluke boats is that they have no deck. Everything is rounded and sealed so that big waves wash over and not in. While the plants are not effected by the rocking action of the boat hull some may need some pruning and training to a system of wires to keep them steady. Inside the greenhouse both soil and hydroponics can be used and crop monitoring might include cheap "web cams". When it comes time to plant, prune or harvest people will go on board for a while. The boat would also be ballasted with under floor fish tanks. Plant wastes would feed the herbivorous fish and the fish would fertilize the hydroponics.
That works on land.
Soil making at sea.
Most of the sea bed is siliceous marine ooze, basalt rock, mineral nodules and larger mineral deposits.  The law of the seas don't seem to mention the first two. Dredged up with semi robotic grabs, these materials could be washed with fresh water and mixed with organic crop wastes these could make good soils.
The oozes are silicon rich. We need to check that there are no toxins like cobalt or copper in the oozes. If we get manganese nodules or gold nuggets "accidentally" then that's just lucky, right? If any major mining operations are done it is reasonable to pay royalties to the relevent entities. The Law of the sea was held up for decades because some fool wanted to spend the money on forced population control. America rightly blocked the ratification but now even China sees the folly of forced population control and is reportedly looking for alternatives. So the door is now open to mining the sea assuming we can make it safe, clean and profitable.
Sand and clay wont be found on the deep sea bed; they dissolve in sea water at various depths. Some countries have ample sand on the sea shore and in their deserts so getting some sand would not be difficult or expensive. Basalt from the sea bed would be useful. Washed and then milled to gravel and dust it could make the mineral portion of a sea soil mix with no trouble. Basalt can also be turned into fibre like glass. Basalt fibre is not as strong as glass fibre and its opaque but it would be a technology to remember. Combined with epoxies basalt fibres sheeting, light hulls, furniture, hydroponic troughs are all possible.
Once the mineral portion of the soil is made then they would be recycled forever or until the boat sinks. Water hyacinth, duck weed, and washed sea weed would add organic matter. Food and crop wastes and fish meal would finish off the mix. It might be wise to add a gutter to our fluke boats and plastic ponds to harvest bird droppings. Dedicated nesting boats are not an impossibility. Guano, bird dropping, are critical to farming on land. Excess use, which is now normal, can lead to soil degradation. That's why our farms are dry deserts most years, blowing away easily and then wash away when the drought breaks; excess phosphate has the effect of stopping plants putting sugars into the soil to feed soil micro-organisms. These micro-oganisms stabilize the soil structure.
These innovations allow the colonization of the open seas with a wide variety of crop options to augment the main crops already discussed by sea steaders. 
Helping save the worlds low islands.
Tuvalu and some other islands are facing problems with rising high tides and sea water infusing into the water table of their farming land and bubbling up through the coral their homes stand on. Storm surges, hurricanes, and tsunamis have always been a threat but today urbanisation, westernisation and the cessation of inter-island nomadism have made these countries more vulnerable. Bubble ponds may help. In this case any depressions are excavated and the fill used to raise the area under or around the houses and used to rase pathways above the king tide level. The depressions will flood and stay flooded. We can then do several things. Build floating houses, toilet blocks and other urban infrastructure. By making these structures float we ensure that they will never flood. By putting them in hole in the coral we prevent them from being washed away in a storm. Another thing is to add lining and fill the depression with soil and irrigate with fresh water. As long as the plastic lining is above the king tide level the soil will remain reasonably fresh. We could float bubble ponds in those depressions that can’t have high enough sides to clear the king tide level. The bubble ponds in the open ocean need to be covered to stop waves breaking over the edge and contamination fresh water. On atolls this is less important and the ponds can be open like a inflatable dingy. Where salt water crops are grown the plastic keeps the  salt water in the pond from contaminating the adjacent fresh water lens in the atolls sand or coral rubble.
Bringing it all togeather. 
Where would I start? The best place to start would be a low coral atoll where food production and opportunities are limited and population is large and growing. Tuvalu, the Maldives or somewhere in the Caribbean. Here sea level rise threatens their land based agriculture. They are dependant on tourism, aid and trade. One good storm could ruin their agriculture, one good war half way around the world could destroy them, diverting the aid or sinking the vital shipping that carries their food to them. Peak oil will have a major impact on shipping prices and fuel for all other purposes. These countries need these solutions, or something like them, now.
Viable Sea steads are being designed by Wayne C. Gramlich, Patri Friedman & Andrew Houser. Design on the right. Using my varient of this design we get the open ocean colony depicted below.
The graphic images here on the left, bellow and above were produced in Second Life.
Thank you Philip and Babbage.
Above image from Sea stead.org
Second Life link.
See Wesley Grommet
Now all we need is some money to start building;  there's plenty of sea. If we can move out over the other 70 percent of the planets surface, the seas, we could increase the planets carrying capacity by several billion. While some may want to get things right on land before pioneering the seas and space; the reality is that pioneering both will give us the skills to cleanup of land based cities and will give us room for those that want large families.  In an era of religous war and often closed boarders having new colonies is essential. Some day you may be seeking freedom far from your home shores. Those new colonies are now possible.

                The end of a beginning.
What about fish farming!?! Fish farming is extremely important to humanities survival and the oceans ecological stability. We farm the land but we still hunt the seas unsustainably.  I have a page on this pending. Please be patient.
wesleybruce -at- iinet . net . au
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