Growth rates of North Sea macroalgae in relation to temperature, irradiance and photoperiod
© Biologische Anstalt Helgoland 1980
Three eulittoral algae(Ulva lactuca, Porphyra umbilicalis, Chondrus crispus) and one sublittoral alga(Laminaria saccharina) from Helgoland (North Sea) were cultivated in a flow-through system at different temperatures, irradiances and daylengths. In regard to temperature there was a broad optimum at 10–15° C, except inP. umbilicalis, which grew fastest at 10 °C. A growth peak at this temperature was also found in four of 17 other North Sea macroalgae, for which the growth/temperature response was studied, whereas 13 of these species exhibited a growth optimum at 15 °C, or a broad optimum at 10–15 °C. Growth was light-saturated inU. lactuca, L. saccharina andC. crispus at photon flux densities above 70 µE m−2s−1, but inP. umbilicalis above 30 µE m−2s−1. Growth rate did not decrease notably in the eulittoral species after one week in relatively strong light (250 µE m−2s−1), but by about 50 % in the case of the sublittoralL. saccharina, as compared with growth under weak light conditions (30 µE m−2s−1). In contrast, chlorophyll content decreased in the sublittoral as well as in the eulittoral species, and the greatest change in pigment content occurred in the range 30–70 µE m−2s−1. Growth rate increased continuously up to photoperiods of 24 h light per day inL. saccharina andC. crispus, whereas daylength saturation occurred at photoperiods of more than 16 h light per day inU. lactuca andP. umbilicalis.