Cultivating Palmaria palmata - Bord Iascaigh Mhara

the tanks via a pipe system where the final diameter of the pipes is 2.0-2.5 cm when they reach the
aeration device. Valves in each line enable adjustment of air flow into each individual tank (Fig. 8.2).
Light: Outdoor tanks may need semi-transparent screens or blinds to reduce light levels and thus
avoid bleaching of Palmaria fronds. A black mesh with small mesh size may be sufficient to prevent
bleaching. Shade cloth mesh tarpaulins used in fish aquaculture are, for example, available in different
grades of shading. Such screens will also reduce the growth of high-light requiring, opportunistic algae
that may compete with the Palmaria, although such competitors should not be a problem if the initial
stocking densities are high (see Chapter 8.2).
Temperature: Optimal temperatures are between 8 and 12°C, and Palmaria will not grow well if the
water temperature exceeds 15°C. In some parts of Ireland, therefore, it may be necessary to cool the
seawater going into the tanks in summer. Cooling units can be inserted into the seawater supply
system. Holding tanks should be well insulated in order to maintain the ambient temperature of
seawater. Any periods of low water temperature in winter should not cause problems in a flow-through
system but, with interval-flushing, there may be significant decreases in water temperature when the air
temperature falls below freezing, because of the large surface area of tanks containing 1000 litres or
more. Variations in water temperature may be reduced by double-walled tanks, or by covering the tanks
at night.
8.1.2 Indoor tanks for algal cultivation
Culture tanks for seaweed may be integrated into an existing shellfish or fish farm with indoor cultivation tanks.
The set-up of algal culture tanks depends strongly on the existing facilities and the space available. The
requirements with respect to tank size, shape, aeration devices, temperature control and drainage are the same
as for outdoor cultivation but there will be differences in seawater supply and light.
Seawater supply: Algal culture tanks that have been installed in a shellfish hatchery for the purpose of
producing algae as shellfish feed may be integrated into an existing seawater re-circulation system. This
will enable the seaweed tanks to function as a water cleaning unit for the wastewater from the shellfish
or fish tanks, which will contain nutrients released from the feed residues and faeces of the fish or
shellfish. The combined use of fish/shellfish and seaweed species in one aquaculture operation permits
the waste produced by one aquatic species to be transformed into a product, which can either be
recycled within the operation or sold as a separate product. This is called “Integrated Multi-Trophic
Aquaculture” (IMTA; see Appendix 4, Glossary, for further information).
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