Growth rates of North Sea macroalgae in relation to temperature, irradiance and photoperiod

Abstract

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 in P. 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 in U. lactuca, L. saccharina and C. crispus at photon flux densities above 70 μE m-2s-1, but in P. 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 sublittoral L. 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 in L. saccharina and C. crispus, whereas daylength saturation occurred at photoperiods of more than 16 h light per day in U. lactuca and P. umbilicalis. © 1980 Biologische Anstalt Helgoland.