The tolerance of marine macroalgae from the coastal region of Helgolan
d Island in the North Sea to ultraviolet and visible radiation was stu
died as related to their habitat and the content of amino acids in the
micosporine group. Littoral algae that contained UV-absorbing substan
ces (micosporine-like amino acids), which act as biological screens, e
xhibited high tolerance to UV radiation. The contents of MAAs in the s
pecies studied correlated with the irradiance levels in their habitats
. Increased MAAs levels were also found in algae growing under conditi
ons of high UV irradiance. Deep-sea algae exhibited high sensitivity t
o UV (particularly, to UV-B, 280-320 nm) radiation. Most sublittoral s
pecies that did not occur in the drying zone (on the littoral) had no
protective pigments. It is supposed that, during their evolution, thes
e species permanently inhabited deep waters or lost their protective m
echanisms. The tolerance of macroalgae to UV radiation depended on the
ir age, germinating spores being the most sensitive growth phase.