Table 3.

Chemical composition of vent fluids and seawater used in this study.

Sample	T (°C)	pH	Mg	Na+	Ca2+	K+	Fe2+ (μM)	Cl-	Si	CH4 (μm)	H2S	H2 (μm)	ΣCO2 (mm)	${\mathrm{N}\mathrm{H}}_{\mathrm{4}}^{\mathrm{+}}$(μM)	${\mathrm{S}\mathrm{O}}_{\mathrm{4}}^{\mathrm{2}\mathrm{-}}$	${\mathrm{N}\mathrm{O}}_{\mathrm{3}}^{\mathrm{-}}$ (μM)
Bruse	229	4.7	15.1	377	27.9	34.3	7.3	469	8.9	5400	0.41	10	174	33.0	ND	ND
Soria Moria	50	6.0	50	432	11.9	12.5	4.0	521	0.8	0.4	0.18	0.30	1.7	5.8	27.3	13.3
Seawater∗	1	7.9	52	442	10.2	9.8	ND	545	ND	ND	ND	ND	2.3	ND	27.9	12.0

^∗The temperature of ambient bottom seawater is -0.4°C at both vent fields, but was set to 1°C in the models. In addition to the listed chemical species, seawater also includes 405 μm O₂. For the Bruse chimney, reported values are endmember values after Mg correction, except for the Mg concentration itself which indicates the concentration in the sampled fluids. Fe²⁺, NH₄⁺ and NO₃^- are given in micromolar (μM), CH₄ and H₂ in micromolal (μm), and CO₂ in millimolal (mm). All other concentrations are given in millimolar (mM). ND, not detected.