Gf f glass microfibre filters

The six large mesocosms and the 12 microcosms were sampled (1 L) for sestonic C, N, and P and for the microplankton abundance, Chl a concentration, and PP. Samples for C, N, P, and Chl a, were immediately transported to the laboratory in cold, dark, and thermally insulated containers. In the laboratory, a volume of 300 mL from each sample was filtered onto pre-combusted GF/F Whatman filters (450 °C for 1.5 h) for seston elemental analysis, filters were dried at 60 °C for 48 h and stored at −20 °C until analysed. C and N were analysed on a Perkin Elmer 2400 (Perkin Elmer, USA) (La Caldera) and Thermo Finnigan EA1112 (Thermo Finnigan, Italy) CHN (Los Cántaros) elemental analyzers and P was analysed with persulfate digestion followed by molybdate reaction⁶⁰ . Chl a was measured by filtering a volume of 300 mL at <100 mm Hg onto Whatman GF/F glass microfibre filters (25 mm in diameter) and extracting in a 90% acetone solution (at 4 °C for 24 h in the dark). Determinations were made in a Turner AU 10 fluorometer in Los Cántaros and LS 55 Perkin Elmer fluorometer in La Caldera⁶⁰ . To quantify abundance of phytoplankton, heterotrophic nanoflagellates (HNF), and small ciliates, we followed the procedures described in Medina-Sánchez et al.^{12 (link)} (Supplementary text S4).

Biomass productivity was calculated from biomass concentration obtained on days two and fifteen. Briefly, the biomass concentration was determined by dry cell measurements carried under mild vacuum filtration. Ammonium bicarbonate (0.5 M) was used to wash the GF/F glass microfibre filters (Whatman). Filters (F) were previously dehydrated at 60 °C for at least 24 h proceeded by silica chambers for 1 h, before (F1) and after (F2) biomass retention. Dry cell weight corresponding to biomass concentration was obtained in g L⁻¹ and calculated according to Eq. 1. Biomass productivity was calculated according to Eq. 2. $$Biomassconcentration{C}_x\left(\frac{\text{g}}{\text{L}}\right)=\frac{F2-F1}{Volumeofculture}$$ $$Biomassproductivity{R}_x\left(\frac{g}{L·day}\right)=\frac{\mathrm{\Delta }{C}_x}{daysofcultivation}.$$