ABSTRACT
Chloropigments (i.e. chlorophylls and derivatives) were analyzed during a
phytoplankton spring bloom and in cultures simulating bloom conditions. Measurement
techniques are discussed, with emphasis on HPLC methods. Ion-pair chromatography
was used for chloropigment analysis in this study. The laboratory investigations showed
that senescence and nutrient-depletion, studied in batch and turbidostat cultures of
Phaeodactylum tricornutum, caused a general decrease in the cellular concentration of
chloropigments when growth conditions deteriorated. The relative proportion of
chlorophyll a increased, while that of chlorophyll c decreased, when growth rate
declined. Variability between cultures and between studies was observed.
Chlorophyllides and allomers of chlorophyll a generally considered decomposition
products of chlorophyll a were related more to active growth than poor physiological
condition in these experiments. Darkness caused an increase in the concentration of the
major chlorophylls, as reported in earlier studies. No clear effects were noticed on other
pigments.
These laboratory observations were not directly applicable to the field study in
Bedford Basin which revealed more complexity than simple batch growth due to the
simultaneous occurrence of changes in physiological condition, grazing and destruction
of pigments by various means. The phytoplankton cells present in the bloom in early
March were mixed to the deeper layers of Bedford Basin about one week later. They
were probably grazed shortly after. A pigment budget was constructed to compare the
various factors affecting the distribution of chloropigments. It identified pigment
destruction as a process potentially important in the quantitative use of chloropigments
as in the recent models of SooHoo and Kiefer (1982a,b) and Welschmeyer and
Lorenzen (1985).