Cultivating Palmaria palmata - Bord Iascaigh Mhara

50
higher running costs than does interval flushing, especially when bigger tanks are used. Interval flushing
involves pumping seawater into the tanks at intervals to exchange a certain volume every hour (or
longer time period). High and continuous flow-rates have the most positive effect on growth of Palmaria,
but interval flushing combined with strong water circulation, driven by aeration in the tank, can be nearly
as efficient as continuous flow-through.
Aeration: Aeration is essential for good growth and health of Palmaria. The water movement created
by aeration fulfils two important tasks: a) movement of algae in the water to enhance nutrient uptake
and thus growth, and b) movement of algae in a circular flow from the surface to the bottom and up
again to minimise exposure to high light intensities, especially in summer, and thus to avoid bleaching of
Palmaria fronds. Bidwell et al. (1985) were the first to develop the principle of tumble culture using
specific air agitation for the cultivation of Chondrus crispus but it has been applied to the culture of other
algal species, including Palmaria (Pang & Lüning, 2004). Fig. 8.1 shows types of aeration suitable for
circular and rectangular tanks. Circular tanks are best aerated by a central pipe with an air outlet at the
bottom. A weight will hold the pipe in place (Fig. 8.2). Aeration devices can be home-made quite easily
or bought in. Rectangular tanks should be fitted with a pipe running along the whole length of the tank in
the middle of the floor. Holes should be drilled at intervals in this pipe for the air to escape and bubble
up to the surface.
Fig. 8.2. Experimental 200-L tanks for Palmaria cultivation. Left: Overview of set-up. Arrows indicate the
main supply pipes for air (blue) and seawater (grey). Middle: Seawater is supplied through a tube (2 cm
diameter; white box) and air by a central pipe. Right: Aeration pipe with weight at the bottom made by
filling a flowerpot with concrete.
The capacity of the air blower required depends on the size of the aquaculture system. It may be
advisable to build in some surplus capacity, since that will allow the tank system to be expanded if
required. A stand-by air blower should also be purchased to replace the main one in emergency.
Without aeration of tanks, Palmaria starts to decay in a few days. Air is distributed from the air blower to