Samples of soft coral Sinularia flexibilis were collected in February, May, August, November in Nha Trang, Khanh Hoa. The content of molecular species in phosphatidylethanolamine class in the lipid of obtained coral samples has been determined. Identified 14 types of PE molecule species, in which the alkenylacyl PE 18:1e/20:4 has the highest concentration, ranging from 51.35% to 63.16% in 4 samples, the highest and lowest concentrations were in a sample collected in August and November, respectively. Samples collected in August and May have a lower diacyl PE ratio than samples collected in November and February. This study identified the lowest alkylacyl and the highest alkenylacyl concentration in a sample collected in August. The fatty acids present in this class are 17:1, 18:1, 18:2, 19:1, 20:4, and 24:5. The percentage of the total content of molecule species by each fatty acid is similar between months. The total content of molecule species containing 20:4n fatty acids was 80.08–84.27% of the PE class, and the difference was not significant in 4 coral samples. There was an inverse correlation between the total content of molecule species containing 20:4n PUFA and the total content of 20:4n fatty acid and the proportional correlation between the content of PE molecule species containing 24:5n PUFA content of 24:5n fatty acid in total fatty acids.

The samples of soft coral Sinularia flexibilis were collected from January to December in one year from Nha Trang, Khanh Hoa coastal. Initial assessment the month-by-month fluctuation of total lipid content and lipid classes composition in this species was conducted. Total lipid content reached the highest value during March to May, lower in the period of June-September and bottomed in October and November. There was a significant decrease in this content between May and June; September and October; the content increase from February to March but not stable during October to February. The lipid classes composition of Sinularia flexibilis includes polar lipids (PL), sterols (ST); triacylglycerol (TAG), monoalkyldiacyl-glycerol (MADAG), wax (W) and free fatty acids (FFA). The concentration of PL in summer (April-August) was lower than that in winter (September-February), this content increased significantly during November-December meanwhile it was observed to decrease in April-May, December-January. The content of ST increased from October to March and declined from April to September. The remain classes including W, MADAG, TAG tend to increase in the summer period and decline in the other months. The fluctuation of lipid classes composition throughout the year is closely related to the presence of zooxanthellae microalgae in corals at different times of the year and is directly influenced by environmental conditions, especially sea water temperature. In addition, the effect of maturation and reproduction of this coral with the increase or release of reproductive materials also observed.

We conduct a study to investigate the year-round fluctuation of lipid composition and content in Pacific oysters (Crassostrea gigas) cultured in Van Don, Quang Ninh, for the first time. Our results showed that the total lipid content of oysters ranged from 1% to 1.6%, with the highest levels observed during their pre-reproductive period (July and December). Polyunsaturated fatty acids were the most abundant type of lipids in oysters, ranging from 41.66% to 53.36%. We identified six lipid classes in Pacific oysters, with the three dominant classes being PoL, ST, and TG, which exhibited significant variation, with the highest variability observed in May and June and the lowest in July. The primary fatty acids in oyster lipids were 14:0, 16:0, 18:0, 18:1n-7, 20:4n-6, 20:5n-3, and 22:6n-3. In summary, our study provides novel insights into the lipid composition and content of Pacific oysters cultured in Van Don, Quang Ninh.The results demonstrate the temporal variability in lipid classes and fatty acid composition throughout the year, with the highest lipid content observed during the pre-reproductive period. These findings could contribute to better understanding the nutritional value of Pacific oysters and inform future aquaculture practices.

The coral Millepora platyphylla was collected for 12 consecutive months in the Nha Trang, Khanh Hoa, coastal areas to study their lipid content and composition. The total lipid content (dry weight) ranged from 0.26–0.63%. The total content tends to increase in the summertime and decrease in the wintertime and there is a correlation with the ambient sampling temperature. The fatty acid class (FFA) accounts for less than 2% of the total lipid. The sterol class (ST) ranged from 6.81–9.86%, polar lipid (PL): 11.07–18.92%, monoalkyldiacylalycerol (MADAG): 18.41–22.78%, wax layer (W): 18.65–25.0%, trialkyldiacylalycerol (TAG) accounted for the largest proportion in total lipid, ranged from 27.58–35.32%. The seasonal variation is significant: the content of FFA, ST, PL decrease during summertime and increase in wintertime, and in contrast to the class of MADAG, W, and TAG. The lipid reverse class (TAG, MADAG, W) is more stable than structural lipid classes (PL, ST). The decrease in W between samples collected in September-October, the TAG concentration between the sample in October-November, the high distribution of the PL concentration in December might closely related to the changing habitat, such as seasonal water temperature and solar radiation, as well as the maturation and reproduction of Millepora platyphylla.

This study aims to analyze compositions of lipid classes, phospholipid subclasses and fatty acids in two mussels, Beguina semiorbiculata, harvested from Nam Du and Phu Quoc islands, Kien Giang province. The obtained results indicated that the total lipid contents of the B. semiorbiculata harvested in Nam Du and Phu Quoc islands were 0.48% and 0.63% of wet weight, respectively, and contained six classes: Hydrocarbon and wax (HW), triacylglycerol (TAG), free fatty acids (FFA), sterol (ST), polar lipid (PoL), and monoalkyl diacylglycerol (MADAG). Two main classes in the total lipid content of two studied mussels were triacylglycerol (TG) (38.22% and 41.27%) and polar lipid (PL) (27.02% and 30.46%). PL of both muselles consited of five types: Phosphatidylethalnolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI) and ceramide aminoethylphosphonate (CAEP) in which phosphatidylethanolamine (PE) (34.34% and 37.08%) and phosphatidylcholine (PC) (26.32% and 26.54%) were dominated. The content of polyunsaturated fatty acids (34.41%) in the total lipid of B. semiorbiculata collected in Phu Quoc was higher than that (26.36%) in Nam Du. The content of n-3 and n-6 fatty acids (20:4n-6, 20:5n-3, 22:6n-3) was high in the composition of fatty acids of both mussels.