Production of intracellular and extracellular algal hpid classes was examlned over a range of rates of supply of Inorganic nitrogen The marine dlatom Phaeodactylum tncornutum was studied using 2 new techniques Cage culture turb~dostdts wt rl used for growing the phytoplankton These are continuous cultunng systems which provldc-a h~g h l y controlled algal environment The Chromarod-Iatroscan TLC/FID system was used for llpid class separat~on and quantification This permitted the resoluhon and detechon of as many as 10 algdl lipid classes plus an lnternal standard for accurate quanhflcauon Up to 3 cultunng units were supplled wlth medium of known nutrient content simultaneously, and particulate intracellular hplds together wlth d~ssolved hplds in the effluent media were monitored Intracellular synthesis of a storage class, triglycende, was clearly triggered by nltrogen stress, whlle synthesis of membrane-assoc~ated polar lipid cIasses was reduced under these conditions Partlculate tnglycerlde yield was higher at lower levels of nitrogen supply despite lower growth rates Different amounts and different types of dissolved extracellular lipid classes were produced under nitrogen-stressed and nitrogen-replete condltlons

The Chromarod-Iatroscan TLC/FID system was used to measure h p~d classes in the dissolved and particulate fractions of seawater samples taken dunng spnng blooms In Bedford Basln, a small inlet in eastern Canada. Polar hpids were the major dissolved lipids present during the bloon~s. Dissolved l i p~d t~m e series indicate decreased phytoplankton exudation and increased bacterial uptake of lipid classes at the t~m e of the chlorophyll maximum. There is evidence to suggest algal uptake of dissolved phospholip~ds. T h~s polar l i p~d class may be used by autotrophs as a source of N and P when inorganic nutrient levels are depleted. The energy-rich storage component, triglyceride, became the major particulate lipid class from the time of the chlorophyll maximum onwards. Other particulate hpid classes present after the chlorophyll maxlmunl suggest that in addition to increased energy storage, there was a greater degree of degradahon of hplds and larger numbers of microheterotrophs.

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