GROWTH AND REPRODUCTIVE PHENOLOGY OF 9 INTERTIDAL ALGAE ON THE MURMANCOAST OF THE BARENTS SEA

Monthly replicate samples of 30 plants of each of nine species were co llected in the intertidal zone in the Dalnezelenetskaya Inlet, Murman coast, Barents Sea. Germlings and new shoots emerged in great quantiti es in March when temperature was near 0 degrees C and daylength 10-13 h. All nine intertidal species on the Murman coast exhibit a period of rapid vegetative growth in early spring, at temperatures far below th e optimum temperatures in at least five of them for which experimental evidence from the literature is available. The increasing light level in early spring is probably responsible for this growth. In six of th em (Ulvaria obscura, Monostroma grevillei, Chorda filum, Chordaria fla gelliformis, Stictyosiphon tortilis, Dumontia contorta) summer peaks o f reproduction are apparently responsible for the summer decline of th e thalli. The last five of these six have heteromorphic life histories in which microthallus stages are thought to ensure approximate synchr onization of early spring recruitment (for instance by short day induc tion of microthallus development at autumnal temperatures, as in D. co ntorta and M. grevillei). In one species (Membranoptera alata), with a n isomorphic diplohaplontic life history, early spring recruitment is thought to be ensured by the release of tetraspores and carpospores in winter. Earlier expectations that southern species would shift their reproduction to the summer near their northern distribution boundary w ere not confirmed. The general conclusion is that each of the nine spe cies has approximately the same seasonal cycle of growth and reproduct ion in various parts of its geographic range, with only minor shifts f rom spring towards summer (but precise data on seasonal cycles elsewhe re are scarce). This suggests that there may be subtle differences in temperatures and photoperiods triggering the onset of reproduction; th is aspect needs further experimental testing of strains from the Murma n coast.