Abstract
Linear growth of Laminaria saccharina (L.) Lamour. and L. solidungula J. Ag. sporophytes exposed for 9 months of darkness under a turbid ice canopy were compared over a 2-yr period in the Alaskan Beaufort Sea. Peak growth in L. solidungula (1.4 mm · day −1) occurred from late February to late April. Maximum growth in L. saccharina (4.7 mm · day −1) was recorded between late April and late July. Since the dark period extends from about November to June, L. solidungula completed most of its growth in complete darkness. During the dark period, from November to late April, linear growth was 1.5 to 8 times greater than that of L. saccharina. In contrast, L. saccharina completed nearly all of its annual growth during the period when light first starts to penetrate the water column as a result of breakup of the ice canopy. The period of rapid growth in L. saccharina occurs 4 to 5 months later than plants found at temperate latitudes. The seasonal pattern of linear growth in the two species differs because L. saccharina does not appear to depend on stored carbon reserves for winter and spring growth. The delay of growth in the ubiquitous L. saccharina to late spring reflects a different growth strategy than that found in L. solidungula.
Published Version
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