Table 1 Oxygen concentrations throughout the first 4 mm of the mat measured at 100 µm resolution using microsensors, measured on 22 August, 2019.

Layer (mm)	O₂ (µM)	NH₄⁺ (µM)	NO₃⁻ (µM)	PO₄⁻ (µM)
1 (0–1)	200–800	34.1 ± 12.8	33.2 ± 10.9	5.5 ± 1.3
2 (1–2)	0–1200	58.6 ± 27.5	30.3 ± 2.8	2.6 ± 0.3
3 (2–3)	0–200	110.8 ± 62.4	30.5 ± 3.7	3.1 ± 0.7
4 (3–4)	only detectable under very high light	109.2 ± 52.7	30.5 ± 3.7	3.1 ± 0.7
5 (4–5)	nd	116.5 ± 69.0	30.6 ± 10.9	2.7 ± 1.2
6 (5–6)	nd	115.6 ± 38.4	30.6 ± 10.9	2.7 ± 1.2
7 (6–7)	nd	124.0 ± 34.3	26.05 ± 5.2	4.6 ± 0.7

Ranges are based on oxygen measurements taken over the course of the day at approximately 15 min intervals. Ammonium, orthophosphate, and nitrate were measured at 1 mm resolution in porewater samples extracted from the mat using a centrifugation technique. Microbial mat was cored using a corer made from a 50 cc syringe and sectioned at 1 mm intervals with razor blades. Mat slices were placed into perforated cups made from 15 mL Nalgene bottles which were then placed into 50 mL centrifuge tubes. Upon centrifugation at 2500 rpm for 5 min at room temperature, porewater left the mat, went through a glass fiber filter (Whatman GF/C) located at the bottom of the perforated cup, and collected in the bottom of the centrifuge tubes. Typically, 100 to 500 µL of porewater was recovered from each 1 mm mat slice. Average values ± standard deviation of the concentration of ammonium (NH₄⁺), nitrate (NO₃⁻) and phosphate (PO₄⁻) in a hypersaline microbial mat at different depths. The depths shown are Layer 1 (0–1 mm from surface), Layer 2 (1–2 mm from surface), Layer 3 (2–3 mm from surface), Layer 4 (3–4 mm from surface), Layer 5 (4–5 mm from surface), Layer 6 (5–6 mm from surface), Layer 7 (6–7 mm from surface); nd: not detectable.

Search