Quantification of multiple environmental controls on lipid biomarkers in common marine diatoms and dinoflagellates

Abstract

Ocean-related global changes have altered phytoplankton community structure, especially the diatomdino agellate competition, which further in uences ecosystem structure and functions. The pivotal ecological roles of diatoms and dino agellates are strongly related with their biochemical compositions, while quantitative comparisons of biochemical changes between diatoms and dino agellates under variable environments are still limited. We investigated responses of lipid biomarkers (sterols and fatty acids (FAs)) to different temperatures (12, 18 and 24℃), nitrogen and phosphorus concentrations and their molar ratios (N:P ratio) of 10:1, 24:1 and 63:1 in marine diatom Phaeodactylum tricornutum and dino agellate Prorocentrum minimum. Over these wide ranges of temperature and nutrient conditions, sterol and FA pro les were relatively stable in the two species. For C-normalized contents of major sterols and FAs, warming caused non-signi cant changes in the diatom but an increase (up to 153%) in the dino agellate; eutrophication caused an overall decrease (up to 53%) in the diatom but an overall increase (up to 77%) in the dino agellate; in contrast, imbalanced N:P ratios caused an overall increase (up to 64%) in the diatom but an overall decrease (up to 53%) in the dino agellate. Under future ocean warming, eutrophication and imbalanced N:P ratios, major sterol and polyunsaturated FA contents would increase (ca. 9% ~ 48%) in the dino agellate, while those in the diatom would change non-signi cantly. This study expands our knowledge on lipid-based indicators of phytoplankton under changing environments, which by systematically linking with several other aspects of food quality will help to understand the ecological role of diatom-dino agellate community changes.

Vertical distributions of lipid biomarkers in spring and summer in coastal regions of the East China Sea

“…FIGURE 7 PCA biplot based on the proportions (%) of lipid biomarkers at each station in the surface and deep layer in spring 2017 and summer 2018. negative correlations between EPA and TSW proportions and nonsignificant correlations between DHA and TSW proportions in summer, which can explain significant positive correlations between and TSW proportions. A high level of EPA is a characteristic FA pattern in diatoms (Kelly and Scheibling, 2012;Bi et al, 2014;Cao et al, 2023). The TSW is derived from the South China Sea Warm Current Water (Bian et al, 2013) and characterized by low nutrient concentrations (Chen, 1996;Zhang et al, 2019).…”

“…The TSW is derived from the South China Sea Warm Current Water (Bian et al, 2013) and characterized by low nutrient concentrations (Chen, 1996;Zhang et al, 2019). A recent laboratory study reported significant positive effects of nutrient concentrations on carbon-normalized concentrations of EPA in marine diatom Phaeodactylum tricornutum (Cao et al, 2023). Thus, EPA production in diatoms may reduce in low-nutrient regions where TSW proportions were high, resulting in high DHA/EPA in the surface layer in these regions in summer.…”

“…This seasonal pattern may be related to the increasing proportion of TSW from spring to summer, with high proportions of TSW occurred only in the southern region (stations G4 and H5) in spring and throughout the study region in summer (Figure 3). In addition, laboratory experiments showed that characteristic FA profiles of phytoplankton classes underlie fluctuations according to culture conditions (Bi et al, 2014;Cao et al, 2023). Environmental changes can alter the production of lipid biomarkers, e.g., up to ca.…”

“…Environmental changes can alter the production of lipid biomarkers, e.g., up to ca. 103% increase observed in carbon-normalized concentrations of EPA in the diatom P. tricornutum under high nutrient conditions (Cao et al, 2023). Thus, the variations in water mass distribution and proportions, as well as associated environmental drivers (e.g., nutrient concentrations), should be systematically considered when applying lipids as proxies of phytoplankton community, particularly in highly dynamic coastal regions.…”

“…Fatty acids and sterols are crucial components in all eukaryotic cells, while in marine ecosystems, essential FAs and sterols are mainly produced by phytoplankton (Dalsgaard et al, 2003;Volkman, 2003). Besides being applied as nutritional quality indicators, FAs and sterols can be also used as phytoplankton chemotaxonomic biomarkers, as the presence and combinations of certain FAs and sterols are characteristic of particular phytoplankton classes (Dalsgaard et al, 2003;Cao et al, 2023). Previous studies have reported the distributions of FAs and sterols in suspended particles in the ECS (Sicre et al, 1994;Shin et al, 2003;Nakanishi et al, 2012;Wu et al, 2016;Cao et al, 2022), as well as other coastal regions in the world oceans (e.g., Tolosa et al, 2003;Mayzaud et al, 2014;McLaskey et al, 2024).…”