The PC1 loading plot suggests that ASP2-grown nutrient-stressed cells are clustered towards the negative side of the PC1 axis as a result of having higher (negative on loading plot) carbohydrate peaks (vC–O of carbohydrates at 1160, 1086, 1050 and 1036 cm−1) and a total lipid peak (vC_O of ester functional groups from lipids and fatty acids at 1745 cm−1), as well as a reduction (positive on loading plot) in protein peaks (vC_O of amides associated with proteins; amide I at 1655 cm−1 and δ N–H of amides associated with protein; amide II at 1545 cm−1) (Fig. 3c). Relative quantification of carbohydrate and lipid content by calculating carbohydrate:amide I and lipid:amide I peak height ratio values (Fig. 3d) demonstrated that
both metabolic classes are significantly higher in the nutrient stressed seawater grown cells than in fertiliser-grown cells.