## 2 Materials and Methods
### Biomass Proxies, Growth Rates, Light Utilization and CO\({}_{2}\) Uptake
The compounds were quantified using GC/HRMS (EI) and/or GC-qToF (ECNI). Proper identification and quantification were confirmed based on correct retention time, correct isotope ratio, a signal/noise ratio > 3:1 and a correct recovery of internal standard, in addition to accepted blank for the method. For dioxins and non-ortho PCBs (no-PCBs), extraction and clean-up were performed with a semi-automated three-column system as described in detail by [PERSON] et al. [103]. In brief, 5 g of freeze-dried tissue was homogenized with anhydrous Na\({}_{2}\)SO\({}_{4}\), spiked with internal standards (13C-labelled polychlorinated dibenzodioxins (PCDD), polychlorinated dibenzofurans (PCDF) and coplanar PCBs) and subjected to extraction and clean up through three columns prepared with (a) activated silica and potassium silica, (b) silica and (c) activated carbon with dichloromethane (DCM) and cyclohexane (1:1) followed by DCM. Finally, the PCDD, PCDF and coplanar PCBs were eluted from the column with activated carbon using toluene. The toluene extracts were attributed to solvent exchange to hexane and further cleaned through consecutive sulphuric acid-coated silica column, followed by potassium hydroxide-coated silica column with hexane, followed by 1% DCM in hexane. \({}^{13}\)C-labelled 1,2,3,4-TCDD recovery standard was added before analysis by HRGC-HRMS-EI (an HP5890 GC coupled to a VG AutoSpec) by monitoring at _m/z_ of the molecular ions. The separation of the congeners was carried out on a DB-5 ms (30 m, 0.25 mm, 11 \(\upmu\)m film thickness) fused silica. For the analysis of perfluorinated alkylated substances (PFAS), the freeze-dried samples (0.4-0.9 g) were homogenized. Internal standards were added to the sample before it was extracted with methanol or acetonitrile using vortex and ultrasonication. After extraction the sample was concentrated followed by clean-up with emulsified carbon. The anionic PFASs were analyzed according to [103]. Quickly, the samples were analyzed by ultrahigh pressure liquid chromatography triple quadruple mass-spectrometry (UHPLC-MS/MS). Analyses were performed on a Thermo Scientific quaternary Acela 1250 pump, with a Waters Acquity UPLC HS 3 T column (2.1 \(\times\) 100 mm, 1.8 \(\upmu\)m) coupled to a Thermo Scientific Vantage MS/MS (Vantage TSQ). Ionization was conducted in the negative electrospray ionization mode (ESI-). The QA/QC of the sample preparation and analysis was assured using mass labelled internal standards for (13C PFAS), where they were available. Quality of sample preparation and analysis for conventional PFASs was further assured with reference materials and laboratory blanks. To analyze (heavy) metals, the samples were digested by microwave-assisted mineralization using an UltraClave. About 0.5-0.75 g of sample was weighed in TFM tubes, and 5 mL of diluted supra pure nitric acid was added. The samples were submitted to a four-step program with 220 \({}^{\circ}\)C as maximum temperature. After digestion, the sampleswere split into two aliquots, and concentrated HCl was added to the aliquot used for Hg determination. Metals were analyzed applying an ICP-MS.  
For all environmental contaminant analyses, the limits of detection (LOD) were calculated for each sample, using the accepted standard method, i.e., the average of blanks plus 3 times the standard deviation for blanks. For metals, blank values were subtracted from the detected concentrations.