Particulate and dissolved lipid classes in cultures of Phaeodactylum tricornutum grown in cage culture turbidostats with a range of nitrogen supply rates

Abstract

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

Time series of particulate and dissolved lipid classes during spring phytoplankton blooms in Bedford Basin, a marine inlet

“…ST consistently showed a sharp increase on the day of the chlorophyll maximum. This result, coupled with the linear relation between sterols and growth rate in turbidostat cultures (Parrish & Wangersky 1987), suggests that where chlorophyll a values are high, enhanced particulate sterol levels can also be used as an indicator of healthy, actively dividing cells. The second ST peak observed in 1982 (Fig.…”

“…By growing a single species of phytoplankton in a highly controlled environment it s h o d d be possible to examine the rate of production of intracellular and extracellular lipids as a function of the rate of supply of nutrients, provided all other variables are kept constant. This can be done with cage culture turbidostats (Parrish & Wangersky 1987), which provide a means of maintaining a constant population density while preventing the accumulation of exudation products in the medium. Using this culture technique it was found that the rate of production of intracellular triglycendes in the diatom Phaeodactylum tricornutum increased with increasing nitrogen stress, while the rate of production of total lipids actually decreased.…”

“…The rate of production of total dissolved lipids, however, did not change. What did change was the type of lipid compound that was released (Parrish & Wangersky 1987).…”

“…Although this environment is vastly more complicated than any that might be experienced in a laboratory setting, it is still relatively simple by oceanographic standards: there is only a small freshwater input to Bedford Basin and there is a relatively limited exchange of seawater with the open ocean. The Bedford Basin spring bloom has previously been found to include Phaeodactylum tricornutum as the fifth most abundant species in surface waters (Platt et al 1973) and thus it was anticipated that the laboratory experiments (Parrish & Wangersky 1987) would be at least in part directly relevant to the Bedford Basin studies.…”

Environmental and nutritional factors determining seasonal variability in the fecundity and egg viability of Calanus helgolandicus in coastal waters off Plymouth, UK

“…In pelagic ecosystems, the quantity and quality of particulate material is highly variable both temporally and spatially (Jeffries 1970, Kattner et al 1983, Parrish 1987, Frazer et al 1989, Mayzaud et al 1989, Pond et al 1993) and this variability in the nutritional environment is thought to be a significant factor controlling secondary production.…”