The demand of seaweeds nowadays have been increasing. In order to supply the needs, background on seaweeds culture is very important. We must know how to culture seaweeds, handle it with care, the methods to be used, and the environmental factors that may affect the growth of seaweeds.

1. P R E P A R E D B Y :
J E M I M A H D . G U M A L A L
SEAWEEDS CULTURE

2. COASTAL RESOURCES OF ASIA-PACIFIC: ENVIRONMENTAL
ASPECTS
 Most productive zone of the ocean, the coastal zone has
been exploited heavily in the Asia-Pacific region.
 Being the closest to land, therefore, the most accessible
to man, the coastal zone and its resources are also the
most vulnerable to pollution and other influences that
result in the degradation of the coastal environment.
 The destruction of naturally productive ecosystems
such as coral reefs and mangrove swamps continues as
a serious concern.

3. COASTAL RESOURCES OF ASIA-PACIFIC: ENVIRONMENTAL
ASPECTS
 The disposal of wastes, particularly sewage, is a growing
problem near many population centers, sometimes
correlated with negative public health effects.
 While various pollutants such as oil and heavy metals are
evident in some localized areas such as industrial centers,
chlorinated hydrocarbons are more widespread and need to
be monitored.
 The awareness of marine environmental problems and
some measures are being undertaken to address the
concerns.

4. STATUS OF SEAWEED PRODUCTION AND UTILIZATION IN
ASIA
 Coastal areas in many Asian countries are
characterized by well-developed coral reef which
originally support rich fishery resources.
 The rapid increase in population and its concomitant
increasing demands for fishery products, however, are
exerting a tremendous pressure on the productivity of
these resources.
 Many of the coastal areas are at present experiencing
the ill effects of overexploitation.
 Alternative sources of food and livelihood for the
coastal inhabitants are therefore necessary.

5. WORLD SEAWEED PRODUCTION

6. STATUS OF PRODUCTION IN ASIA
 Except for China, Japan and Korea where the
seaweed industry is well established, the rest of the
developing Asian countries are still dependent on
wild seaweed crops.
 The Philippines may be cited as an exception, but
actual farming is still limited to three species,
namely: Eucheuma alvarezii, E.
denticulatum and Caulerpa lentillifera.
 Indonesia is presently producing a certain amount
of Eucheuma. Thailand is starting
her Gracilaria culture project. The rest are still
dependent on wild crops.

7. UTILIZATION OF SEAWEEDS AND SEAWEED
PRODUCTS
 Japan, China and Korea where seaweeds and seaweed products are
standard components of meals of the bulk of the population direct
utilization of seaweeds as food in other Asian countries is limited to a
small portion of the population along the coastal areas.
 Many species of seaweeds are eaten as vegetable salad and
prepared in various ways. Seaweeds in general with the exception
of some species are of low nutritional value due to their low
protein content and generally hard-to-digest carbohydrates.
 However, they are important source of minerals, vitamins and
roughage. Seaweeds are good food supplements and cannot
totally replace the staple foods such as rice, fish and other
cereals. Among those which are utilized directly as food are the
following:
E. alvarezii, E. denticulatum, species of Caulerpa,
Porphyra, Codium, Hypnea, Laurencia, Hydroclathrus,
Acanthophora and Sargassum.

8. UTILIZATION OF SEAWEEDS AND SEAWEED
PRODUCTS
 The high demand for tropical seaweeds in the
international market as raw materials in the
manufacture of commercial products such as agars,
carrageenans and alginates was the primary factor
which influenced the development of farming
technology for some seaweeds like Eucheuma.
 The farming of Eucheuma is a very productive small-
scale industry which can be an alternative fishing
activity in shallow coastal areas.

9. SEAWEED ECOLOGY: INFLUENCE OF ENVIRONMENTAL
FACTORS ON THE STRUCTURE, PHENOLOGY AND
DISTRIBUTION OF SEAWEED COMMUNITIES
 The environmental conditions regulate the kind,
nature, abundance and productivity of seaweed
communities.
 The stature of the community is reflective of the
environmental conditions in the area.
 Different kinds of species are found in certain
habitats because environmental conditions are
favourable to their development.

10. ENVIRONMENTAL FACTORS
 The ambient ecological condition in a certain habitat
is the result of the combined and synergistic effects
of the various ecological factors.
 Some of these factors may exert modifying effects on
the others.
 The understanding of the influence of these
parameters on the nature, biology and distribution of
seaweed is important in the evaluation and
assessment of sites for mariculture purposes.

11. ENVIRONMENTAL FACTORS
Water Temperature
 A water temperature ranging form 25 °C to 30 °C is best for growing
Eucheuma. In shallow waters near the beach, the water temperature can
become quite high especially during a sunny day. Such an area is not
suitable for planting seaweed. In fact, even though you might think that the
shallow sandy bottom is good for securing your stakes, the high water
temperature will kill your plants.
 So, we suggest that you set your farm away from the lowest tide mark
(spring low tide limit). A good area is the one between the spring low tide
limit and the reef edge or an area which does not dry up during these big
low tides occurring during full or new moon.
Water Salinity
 Minimum water salinity required is about 28 ppt (parts per thousand) or
more. Salinity is the term used to indicate the amount of salt you can
measure in sea water. Do not worry! By tasting a few drops of salt water in
your mouth, you can feel the difference in salinity. Brackish water at the
river mouth will taste less salty than ocean flowing water. Be sure that you
do not plant your seaweed in front of a river mouth or in fresh water, as
fresh water will kill the seaweed.

12. Do not set your farm in front of a river mouth.

13. Bottom Type
 A white sandy bottom with the presence of a limited amount of natural
seaweed, is probably the best place to cultivate Eucheuma. If the bottom is
covered with seagrass, Eucheuma will not grow very well. This is because other
seaweeds might compete, absorbing the nutrients from the water leaving your
Eucheuma plants starving. In this situation, your plants might be covered with
unwanted seaweeds and as a result, silt will quickly deposit on them.
 A sea bottom with hard coral formations and coral heads is not a good site to
establish your farm. In such areas it is difficult to secure your stakes. In
addition, plant eating fish generally live and aggregate around coral heads.
From here, they move out from time to time to graze on your seaweed. As a
result, they damage your plants.
 A muddy sea bottom, is also not advisable for your farming site because silt or
mud will cover the plants reducing the seaweed growth and some extra work
will be necessary to shake and keep clean your plants. Also murky water will
limit the amount of sunlight that is supposed to reach your plants.
 Now you can see why we suggest you choose a nice white sandy bottom to set
your farm.

14. Bad Good Bad

15. Water Movement
 Moderate water movement is mostly preferred to strong water
current like the one you can see close to the reef edges or in its
passages. If the water current is too strong, it can damage your
plants and even wash away your planted lines by pulling down
the stakes. It will also slow down your work as it is difficult work
in areas with strong swift current.
 However, be sure that there is a constant exchange of ocean
water as the one you have with the changing of the tides and
sufficient water movement as the one created by waves. This will
bring the necessary nutrients to the plants for a healthy growth.
 As for any type of farming, the supply of nutrients is an essential
factor for growing your crops. This applies to seaweed
cultivation too. Therefore, remember to consider water
movement as an important factor for seaweed growth while
selecting the area for your farm.

16. Seaweed farm set against water current. Strong water current can bend or
even break the lines. This is not a good way to follow.

17. Water current flows into the farm and not against it as above. This is a good example to
follow.

18. Sunlight
 Eucheuma requires sufficient sunlight for growth.
Sunlight is used by Eucheuma as a source of
energy for its growth and to manufacture
carbohydrates like carrageenan, the
commercially valuable substance inside the
seaweed. Thus, it is essential to have plenty of
sunlight. Clear seawater allows sunlight to
penetrate more easily to the plants. This is why
when seaweed is planted close to the sea surface, it
grows faster and healthier compared to that
planted close to the sea bottom or in deep water.

19. GOOD BAD
Seaweed planted in shallow water near the surface (30 to 50
centimeters) receives plenty of sunlight and its growth will be
good.
Seaweed planted in deep water (more than 1 meter from the
sea surface) does not get enough sunlight and its growth will
be poor.
Water Depth

20. Water Depth
 At least knee deep water at spring low tide (0.5 meter) is
the minimum water depth required to cultivate Eucheuma.
In shallower waters seaweed can still grow, but it might be
exposed to direct sunlight and wind. As soon as your
seaweed is exposed to sun and wind, the tender tips of the
plants are destroyed and if exposed for a long time (2 to 3
hours), the whitening of the branches can be seen. This will
indicate that part of the seaweed has been killed. Eventually
branches will break and drift away from the whitened area.
 So, it is important to consider the water depth while
selecting the area of cultivation.

21. Water Pollution
 Because Eucheuma prefers clear water and plenty of
sunlight, even turbid water (muddy) will not sustain
good seaweed growth.
 Chemical pollution will kill the seaweed as in the
case of most marine plants and animals.
 We suggest, after you select one location you think is
good to grow Eucheuma, to plant several lines of
seaweed in various spots within that area and
observe its growth. This will be the best way to find
out the ideal area for farming.

22. Methods Used to Cultivate Seaweeds
 There are at least 3 methods you can use to cultivate
seaweed. They are known as:
 Off-bottom (fixed bottom) Method
 Raft or Floating Method
 Longline Method

23.  Off-Bottom Method
Wooden stakes are driven into the sea bottom 20 to
25 centimeters apart form each other in straight rows.
The stakes should be 5 to 10 centimeter in diameter
and 1 or 1.5 meter long. At least 0.5 meter of the stake
should be driven into the sand to make them secure.

24. A 3 millimeter thick polypropylene rope 5 meters long is firmly stretched between
two stakes. Attached to the 3 millimeter rope (line) are 30 pieces of raffia
(polypropylene strings). Each of your planting material (seed), the size of the palm of
your hand (150 grams), is tied to the raffia strings. The 3 millimeter rope, is
suspended at least 20 to 30 centimeters from the sea bottom to prevent the growing
seaweed from being tossed on the sand and 20 to 30 centimeters below the water
surface at low tide to avoid the seaweeds from being exposed to direct sun light.
Direct sun light will kill the exposed parts.

25. Stakes must be sharpened at one end so that they can be easily driven in the sand. You can
use mangrove stakes or any other bush timber which does not rot easily in sea

26.  In the floating method, seaweed is attached to
some device that keeps the seaweed floating;
rising and falling, with the tidal changes.
 Following this method, be sure to keep the
seaweed about 50 centimeters below the water
surface.
 The floating devise can be a simple frame made of
bamboos, mangrove wood, or bush timber
durable in seawater. You can tie together four 2.5
meter long bamboos into a square frame and
stretch 3 millimeter ropes (lines) inside the
frame.
Raft or Floating Method

27.  In a 2.5 meter square frame, you can stretch up to
15 lines, 10 to 15 centimeter apart. Each line will
carry 15 pieces of seaweed tied to the 3 millimeter
rope with raffia.
 In a frame like the one described, you can plant up
to 225 pieces of seaweed.
 In this method you can tie your seaweed on shore
by placing the raft on a support (oil drums or
wooden posts). In this way it will be easy for you to
tie your seeds to the lines.

29. LONGLINE METHOD
The longline method is similar to the raft or floating
method in several ways.
In fact, seaweed is hung to a rope which is suspended
by floaters. In this method, however, the main rope
is thicker; about 10 to 15 millimeters in diameter.
This rope is tied to plastic floaters or bamboo set at 4
to 5 meters interval and anchored at each end. The
pieces of raffia holding the seaweed, can be tied to
the main rope in two ways.

30. LONGLINE METHOD

31. Remember!
Your seaweed has to be hung near the water surface
to receive sufficient sunlight. You can suspend the
main line about 0.5 meter below the water surface.

32. What are the advantages and disadvantages among these three culture
methods?

33. How to Handle Seaweed?
When you need to transport your
seaweed seeds from one place to
another, as in the case of taking your
seeds to another village or even when
you want to take seaweed at home to
prepare your lines, you should consider
that the seaweed is a living plant and
needs particular care.

34. The first thing you should do, is to cover
your seaweed with tarpaulin or coconut
leaves. If you know that you will be
travelling for several hours moving your
seaweed, it is advised to put it in jute or
onion bags. It is very important to keep the
seaweed moist at all times. You can pour sea
water over the bags or, when you have a
chance, dip the bags in the sea.
How to Handle Seaweed?

35. You can also use styrofoam boxes to
transport your seaweed. In this case, make a
few holes on the upper edges of the box to
facilitate aeration. Remember to keep the
seaweed moist. Do not fill the box with
seawater as this will make the seaweed rot
rapidly unless the sea water is constantly
circulated.
How to Handle Seaweed?

36. How to Handle Seaweed?

37. How to Handle Seaweed?
Even when you carry seaweed seeds on your punt to
the farm site, keep the seeds covered to protect them
from direct sunlight. Pour some seawater over them
at regular intervals. Preparing the lines from your
punt, might take several hours and if not covered
and kept moist, the seaweed seeds will be spoiled.

38. How to Handle Seaweed?
You might wonder why you should cover and keep
your seaweed moist. This is to avoid the seaweed
being exposed directly to sunlight, wind and rain.
Seaweed, needs to be kept moist, cool and protected
to survive out of the water.

39. What can harm the seaweed?
 NATURAL PREDATORS
As frequently observed,
rabbit and puffer fish
are the main seaweed grazers.
In addition to these,
sea urchins and sea turtles
are also often seen
damaging the seaweed plants.
Among all of these,
rabbit fishes are usually
the most destructive.

40. What can harm the seaweed?
 DISEASES
Even though there are no specific diseases that
might affect Eucheuma, in situations where plants
are heavily grazed it is common to observe whitened
areas on their branches.
Whitened areas are more exposed to fungal
infection. Especially during the warmer months,
fungal infection can spread quite rapidly and the
seaweed plants show large portions of discolored
branches commonly seen as white and pink areas.
“Ice Ice” is the common term used to describe
seaweed plants in this condition.

41. What can harm the seaweed?

42. What can harm the seaweed?
 WEATHER
Apart from occasional bad weather (rough sea and heavy rain), the effect of
cyclones occurring during the summer months can be devastating. Cyclones
cannot be avoided, but what you can do is take precautions.
1. During the cyclone season, you should listen to the radio weather forecast
regularly and carefully. If a cyclone is expected, harvest as much seaweed as
you can and keep it on shore protected from wind and rain.
2. Put aside sufficient seaweed to allow you to re-start farming after the cyclone
has passed by. Remember you need to keep this seaweed in bags moist with
seawater at all times. That seaweed will be your re-planting material.
3. If seaweed is kept small during this period, and not allowed to become over-
mature, little damage is expected. You might decide to harvest after 4 or 5
weeks of growth instead of waiting for 6 or 8 weeks. Experience after going
through several cyclones suggest that this strategy could limit your damage.
4. Also, be sure that your stakes are firmly erected otherwise the strong water
currents and swells during cyclones might wash away your effort.
5. After the cyclone has gone through, tangled lines should be entangled and
secured again. Badly damaged seaweed should be completely removed and
replaced with new seeds.
6. If you are heavily hit by a cyclone but you have not lost all your seaweed,
then it is possible to be back in full business again after 8 weeks. A lot of
work has to be done and done quickly, but it will worth it.