Cultivating Palmaria palmata - Bord Iascaigh Mhara

8.4 Monitoring and maintenance
To produce high quality biomass, factors such as light, stocking densities and nutrient supply should be adjusted
as the cultures develop during the course of the year. Several factors should be monitored on a frequent basis:
Growth of Palmaria: Growth is measured as increase in biomass over time (e.g. kg wet weight per
week). The driving factors for growth are light, nutrients and, to a lesser extent, temperature, as
described above.
Colour and integrity of fronds: The algal fronds should show a rich red-purple colour. A change in
colour to green and disintegration of fronds due to parts dying off indicates that the culture conditions
are not right (see Fig. 8.3). The reasons could be: too much light; nutrients depleted in times of rapid
growth; over-fertilisation at times of slow growth; aeration too low and insufficient to tumble the fronds;
fronds too large and too heavy to tumble; flow rate of seawater too small, resulting in too little flushing.
Epiphytes and endophytes: The growth of epiphytes is easily detected. Small green or brown fine
filamentous algae settle preferentially around the stipes of Palmaria and on old thallus parts (see Fig.
8.3) or along the edges, especially where fronds have been torn into smaller pieces. Endophytes are
visible as dark brown spots inside the tissue of older parts of Palmaria thalli. Although endophytes do
not cause any harm to consumers, infected tissue parts will not meet the quality demands for foodstuff
and have to be removed. Epiphytes appear mainly from the spring until autumn. Growth of epiphytes
can be reduced by lowering light intensity and nutrient concentrations in the seawater.
Fig. 8.3. Palmaria from tank cultivation. Left: Individuals which are damaged and/or bleached. Right:
Epiphytic algae growing on the older parts of fronds; new fronds have grown out from the margins of
the lower part of a frond.
Movement of algae in the tanks: As Palmaria is a species which grows best at sites with a strong
current, it is essential to ensure that the water in the tank is agitated by strong aeration and that the
tanks are flushed sufficiently. This should be checked daily because Palmaria thalli die off quickly
without proper movement.
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