## 2 Materials and Methods
### Biomass Proxies, Growth Rates, Light Utilization and CO\({}_{2}\) Uptake
Total Lipid, Lipid Class and Fatty Acids, Protein and Amino Acid Analysis, Environmental Contaminants  
Extraction of lipid followed [PERSON] et al. [94] adapted from [PERSON] method [95], using 2 mL of dichloromethane:methanol (2:1 \(v/v\)) as the extractant per 100 mg of biomass [96]. The pellets were crushed using a mortar and pestle prior to extraction, and the biomass was extracted twice to maximize yield. The organic extracts were evaporated under nitrogen and the total lipid content was determined gravimetrically. Fatty acid methylation was performed using a method adapted from [PERSON] [97], using sulfuric acid as the catalyst. Briefly, 100 \(\upmu\)L of lipid extract (10 mg mL\({}^{-1}\) dissolved in dichloromethane) was transferred to a 15 mL glass tube and added 800 \(\upmu\)Lof dichloromethane, 100 \(\upmu\)L of internal standard (C17:0-0.1 mg mL\({}^{-1}\)) and 2 mL 10% H2 SO4 in MeOH. The samples were then heated and kept at 100 \({}^{\circ}\)C for 1 h, cooled, and 3 mL hexane and 3 mL 5% NaCl in H\({}_{2}\)O was added. The resulting organic phase was transferred to 4 mL glass tubes. Following evaporation, the samples were resuspended in 100 \(\upmu\)L of hexane and transferred to GC test tubes prior to analysis. Fatty acid methyl esters (FAMEs) were analyzed on a GC-FID (Agilent Technologies) coupled to a Select FAME column (length 50 m, ID 0.25 \(\upmu\)m and FT 0.25 \(\upmu\)m, Agilent J&W Columns), using helium as the carrier gas (1.6 mL min\({}^{-1}\)). The fatty acids were quantified based on the peak area of the chromatograms divided by the area of the internal standard and converted to absolute amounts using the slopes calculated from standard curves (triplicates of 7.8125-2000 \(\upmu\)g mL\({}^{-1}\) of GLC 502 Free Acids, Nu-Check-Prep, Elysian, MN, USA). The lipid class composition was analyzed by normal phase HPLC, using a Water e2795 separations module coupled to a SupelcosilTM LC-SI 5 mm (25 cm \(\times\) 4.6 mm) column (Supelco HPLC products, Bellefonte, PA, USA) set to a working temperature of 40 \({}^{\circ}\)C. The HPLC method used was modified from [98]. Lipids were quantified on a Waters 2424 ELS detector based on the peak area in the chromatograms and converted to absolute amounts based on standard curves. The detector settings were as follows: Gain 100, nebulizer heating level set to 30%, drift tube temperature set to 45 \({}^{\circ}\)C and pressure set to 40 PSI. The total run time was 41 min, using the a gradient profile table. All lipid analyses including fatty acids and lipid classes were performed using five replicates. For amino acid analysis dried microalgae (40 mg) was mixed with 0.7 mL distilled H\({}_{2}\)O, 0.5 mL 20 mM DL-norleucin (internal standard) in glass tubes with two replicates and hydrolyzed as previously described [99; 100]. The amino acids were analyzed chromatographically using an ion exchange column followed by ninhydrin post column derivatization on a Biochrom 30 amino acid analyzer (Biochrom Foods 2020, 9, 1901--4 of 17 Co., Cambridge, UK). As described previously, amino acid residues were identified using the A9906 physiological amino acids standard (Sigma Chemical Co., St. Louis, MO, USA) [101]. The total amount of protein was measured as the sum of amino acid residues as recommended by [102]. All contaminant analysis were performed by NILU-Norwegian Institute for Air Research. For the analysis of polychlorinated biphenyls (PCBs), all pentachlorobenzene (PeCB), hexachlorobenzene (HCB) and pesticide samples were prepared similarly. Briefly, 1.5 g freeze-dried microalgae were mixed and homogenized with a 20-fold amount of dry Na\({}_{2}\)SO\({}_{4}\). Prior to extraction, the samples were added to a mixture of several different isotope labelled compounds for quantification purposes. The samples were extracted with organic solvents (cyclohexane/acetone, 1:1) and concentrated, followed by a sulphuric acid clean up and fractionation on a silica column to remove interferences before analysis.