Abstracts now available online - Euro Fed Lipid

P15
Influence of irradiance on fatty acid composition of symbiotic
dinoflagellates of hermatypic corals
Zhukova N. V., Institute of Marine Biology, Far East Branch Russian Academy of
Sciences, Vladivostok 690041, Russia
Lipid production and accumulation by photoautotrophic symbionts is a principal source
of energy for the animal-host. The effect of variation in light intensity on the fatty acid
profiles of symbiotic dinoflagellates (SD) isolated from hermatypic corals Millepora
intricata, Pocillopora damicornis, Seriatopora caliendrum, S. hystrix, and Stylophora
pistillata preferentially subjected to 95%, 30%, 8% and 2% of the incident
photosynthetic active radiation (PARo) was investigated. Irradiance had a significant
effect on fatty acid composition of polar lipids, associated with photosynthetic
membranes and on triacylglycerols, the storage substances of the cells. SD showed
substantial changes in the proportion of 16:0 as a response to variation in PARo. During
adaptation to high light percentage of 16:0 increased in polar lipids and triacylglycerols.
Additionally, percentage of 14:0, 16:1(n-7) increased in triacylglycerols. A substantial
portion of these fatty acids is located in triacylglycerols. Thus, high light conditions
imposed increase in storage products providing utilization of the excess energy for
energy-consuming processes. Polar lipids of SD adapted to low level of PARo had
greater concentrations of 18:4(n-3), 20:5(n-3), 18:5(n-3) and 22:5(n-6) commonly
involved in the formation of thylakoid membranes. Conversely, the amounts of 20:4(n-6)
and 22:6(n-3) increased with increasing irradiance, it may indicate on their association
with photosynthesis. The elevation in the percentage of 18:4(n-3), 20:5(n-3) and 18:5(n-
3) during exposure to low light was accompanied by increase in chlorophyll a content in
the SD cells. It supports the suggestion that chlorophyll molecules are associated with
some specific polyunsaturated fatty acids. In spite of the proportions of individual fatty
acids varied significantly in response to light conditions, in general, the ratio of saturated
and polyunsaturated fatty acids changed slightly in both lipid classes. Hence, variation
in PARo levels did not affect in considerable changes of unsaturation of the membrane
fatty acids. Thereafter the adaptive response of algae to the variation of light intensity in
physiological ranges does not result in the changes in the membrane fluidity. Lightdependent
changes in the fatty acid composition arise, apparently, from correlation of
activity of photosystems with processes of production and desaturation of fatty acids in
algae.