Effects of micro-nutrients and major nutrients on natural phytoplankton populations

Six experiments were carried out with natural phytoplanktonpopulations grown under simulated natural conditions, in anattempt to assess the gross effects of major nutrient and micronutrientperturbations upon the growth and species composition of thesepopulations. Water was collected from Yaquina Bay, Oregon, andfiltered into twenty-litre growth containers. Some of this waterwas treated with activated carbon to remove a portion of thetrace metals and trace organics. Various combinations of majornutrients, micro-nutrients, and chelators were added to thesecultures. Inoculation was with unfiltered bay water, at a ratioof 1:1000. Incubation was in outdoor tanks of water circulatingfrom the bay, under natural sunlight. The major nutrients andmicro-nutrients appeared to have fundamentally different effectson the growth and species composition of phytoplankton. Themicro-nutrients had marked effects on the species compositionof the phytoplankton populations, while major nutrients hadminimal effects on species composition. The micro-nutrientsalso had substantial effects on population growth rates, lagperiods, and final yields. The major nutrients had a substantialeffect only on final yields.