Farm Design
The cultivation method and farm design (which are highly influenced by the individual site conditions), will determine what type of equipment is needed on the seaweed farm. For the grow out at sea, there would generally be some type of anchor, ropes, culture lines and floaters be required. In most cases a boat will be required by the farmer.
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Saccharina
The depth of the water at the farm site is the main indicator what cultivation techniques and therefore farm design will be used for growing the seaweed
In shallow areas (0.3 – 2 meter depths during the lowest lowest tide) the fixed off-bottom method is very common, where wooden or steel stakes are holding lines in place that are suspended below the surface.
In deeper waters, the hanging long-line, floating rack and multiple raft long-line methods will be used. In these countries, seaweed is mainly growing in areas where the sea has a maximum depth of 15 meters.
Fixed-off bottom cultivation
Hanging long-line cultivation
Floating raft cultivation
Illustrations adapted from University Malaya
Going further offshore is not only more expensive, since more material and boat fuel is used, but also exposes the farm to higher risks, due to typically increasing wave height. There are at least a handful of other cultivation techniques and many unique design variations to set up the farm. In the fixed- off bottom and floating rack method the line length usually does not go beyond 10 meters. However in the floating/ hanging long line method the length of each culture line can be much longer and vary quite a bit, depending on the farm location. Less exposed areas can have longer lines, however also the handling of a longer line can be a limitation.
Farm designs highly depend on the location characteristics
60 meter long floating long lines in 8-10m deep water in South Sulawesi, Indonesia.
Fixed off-bottom method in shallow water in Nemberala, Rote Island, Indonesia.
Fixed off-bottom method in high density, due to short distance between culture lines Nemberala, Rote Island, Indonesia.
The different farming methods of eucheumatoids have different material requirements or needs for equipment.
Different anchors
In terms of anchors, wooden stakes are commonly used across all regions. They are set up with pure manpower. In overhead high waters, this requires skilled free divers in the community.
!Good to know! Wooden stake anchors are in some regions preferably made out of mangrove wood because of their durability in the water. However, by law, mangroves in the Philippines and Indonesia are protected.
In most fixed off-bottom farm setups, each culture line will be attached with two wooden stakes.
It takes a lot of strength to hammer the anchor stakes into the sea ground. Once well placed they would last up to two years under normal conditions.
Iron bars are more expensive but usually last much longer than other anchors (approximately 5 years).
Rope material
The culture lines are somewhere between 4 and 7 mm in diameter. In floating long line systems, the lines connected to the anchor (rig lines) are usually stronger (10-14 mm) – the strength of all ropes used depends both on the farm design and exposure of the site.
The lines are a substantial cost in setting up a farm and in most cases common polyethylene ropes (PER) sold in local variety stores or provided to the farmers by the local dealers. The prices for a roll of 200m rope are somewhere between 10 and 15 USD. Under normal conditions, these ropes can last up to 5-8 years. Frequent cleaning of the culture line after each cycle will help to keep them intact and also reduce the contamination of disease, epiphytes or similar.
Preparation of a new culture line consisting of 6 mm polyethylene rope and nylon cord to tie the seedlings. Taytay Bay, northern Palawan in the Philippines.
The culture lines can be reused many times if kept in good conditions. Sabah, Malaysia
Floaters
As floaters, used PET (polyethylene terephthalate) bottles are most commonly used to keep the culture lines floating. In some regions, only one type would be preferred, elsewhere all sorts of bottles are used. Farmers reported large differences in how long these bottles last them. Depending on the type of PET bottle, they would have to be replaced every 2-3 cycles. Although there have been some initiatives to introduce manufactured floaters (rubber floats) from more durable materials, after all the farmers prefer the bottles since they are very cheap and practical. They noticed that the surface of the new introduced floaters allows more biowaste to attach and the additional weight lets them sink faster. The PET bottles on the other hand have a cleaner surface, where this process happens much slower.
PET bottles ready to be deployed as floaters in Honda Bay, Palawan in the Philippines.
Because almost all PET bottles can be used for seaweed farming, they will be collected from the general trash and traded at a fairly high price in seaweed farming regions.
To reduce the pollution from the PET bottles or Styro Foam used as floaters, the government in Malaysia has introduced various new types of floaters, that are also supposed to last longer.
However a big problem with these floaters is the accumulation of biowaste that makes them sink faster.
Styro Foam floaters are probably the worst option for the environment as they slowly disintegrate into small pieces that never completely decompose.
Usually the fixed off bottom method does not require any floaters. However in some cases they are attached so the seaweed lines will stay closer to the surface at high tide. Oenggaut, Rote Island, Indonesia.
Explore another seaweed species:
Eucheumatoids | Saccharina | Undaria | Pyropia | Gracilaria
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