ALLOCATION OF BLADE SURFACE TO REPRODUCTION IN LAMINARIA-LONGICRURIS OF LONG-ISLAND-SOUND (USA)

Sorus formation in the kelp Laminaria longicruris de la Pylaie (Phaeop hyta) was quantified for a biennial population in Long Island Sound (C onnecticut, USA), at the southern limit of its biogeographical range i n the Western Atlantic Ocean. The allocation of blade surface to repro duction was measured monthly during two years, with additional samples taken at times of peak growth and reproduction. Sporophytes produced sori year-round, with the highest percentages of fertile plants (75 to 95 percent) occurring from October to December. The mean percentage o f sorus area to blade ranged from 1 to 37 percent, remaining low and f airly constant during the spring and summer, but reaching much higher levels in the fall (when growth is minimal) and early winter. The comp aratively low mean annual allocation of blade surface to reproduction (5 percent), was postulated to be due to temperature stress on these p lants at the southern limit of distribution, but may instead be typica l of the species. Such a small allocation of resources to reproduction nevertheless results in billions of spores per M2 of substrate, makin g a major contribution of material potentially available to grazing fo od webs.