ABSTRACT
Microscopic Macrocystis gametophytes and juvenile sporophytes were cultured in both natural and artificial seawater media supplemented with various concentrations of the nutrient trace metals copper, zinc, iron, manganese and other elements. Ranges of concentrations tested included levels associated with adverse effects such as growth inhibition and buildup of a metal in the tissues. Our results indicated dependence upon factors affecting biological availability of the metal, both inside and outside the plant. Juvenile Macrocystis sporophytes growing in offshore surface seawater from the Southern California Bight can apparently tolerate additions of about 200 nM copper and 1000 nM of either zinc, iron, or manganese without adverse effects. Macrocystis gametophytes are probably more sensitive than sporophytes to trace metal additions, possibly by as much as an order of magnitude in terms of concentrations tolerated.
