Photosynthetic oxygen bubble stream sounds from aquatic macrophytes, and their consequences for acoustic biodiversity inventories and acoustic communication in shallow freshwater settings

PLOS ONE | https://doi.org/10.1371/journal.pone.0317424 April 23, 2025 6 / 13 PLOS ONE Photosynthetic oxygen bubble stream sounds from aquatic macrophytes Exemplar 2 Recorded on June 20, 2021, this sound was associated with a macrophyte bubble stream, visible from above in shallow (<20 cm) water. This sound ceased with removal of the plant. The sound varied considerably over time, but with an underlying regular oscillation (Fig 2). Long syllables averaged 951.61 ms, with two peak frequencies (1.6–3.5 kHz and 5.3–7.5 kHz). Amplitude peaked numerous times, most prominently in the middle of the recording. Audi- bly, this sound consists of repeated down-slurred “EEeeeuzzz” varying in amplitude over time. Exemplar 3 Recorded on August 1, 2021, in shallow (<20 cm) water in the morning (Fig 3), associated with a bubble stream captured on a waterproof camera. Numerous short syllables averaged 10.11 ms in duration, strung together as an oscillation with more-or-less consistent spacing and amplitude. Peak frequencies ranged from 0.9 to 6.2 kHz. Qualitatively, the short bursts are strung together to produce a whirring sound, overlayed by a lower, more constant buzz. Exemplar 4 Recorded August 1, 2021, Alberta, in shallow (<20 cm) water, associated with a bubble stream captured on a waterproof camera, this sound differed substantially from the others (Fig 4). Table 1. Spread of peak frequency (kilohertz) and average duration of a single syllable (milliseconds) for five exemplar recordings of photosynthetic oxygen

bubble sounds produced by sago pondweed (Stuckenia pectinata). Standard deviation and standard error of the mean are included for both frequency range and duration of syllables. The upper and lower standard deviation and standard error refer to the variability of either end of the mean range given. Values of N/A were unable to be provided as there is only one syllable present (Exemplar 5). Spread of Peak Frequencies (kHz) Duration of Syllables (ms) Mean SD SE Mean SD SE Exemplar 1 1.6–2.6 Lower: 0.35 Upper: 0.40 Lower: 0.06 Upper: 0.70 221.64 30.99 5.39 Exemplar 2 1.6–3.5; Lower: 0.25 Upper: 0.43 Lower: 0.04 Upper: 0.06 951.61 162.41 23.69 5.3–7.5 Lower: 0.33 Upper: 0.21 Lower: 0.07 Upper: 0.02 Exemplar 3 0.9–6.2 Lower: 0.15 Upper: 0.14 Lower: 0.02 Upper: 0.02 10.22 2.40 0.34 Exemplar 4 1.4–1.6; Lower: 0.72 Upper: 0.70 Lower: 0.02 Upper: 0.02 279.45 44.92 13.54 2.9–3.1; Lower: 0.12 Upper: 0.11 Lower: 0.04 Upper: 0.03 4.5–4.7; Lower: 0.16 Upper: 0.18 Lower: 0.05 Upper: 0.05 6.0–6.2; Lower: 0.22 Upper: 0.19 Lower: 0.07 Upper: 0.06 7.6–7.8; Lower: 0.28 Upper: 0.28 Lower: 0.09 Upper: 0.08 9.0–9.4; Lower: 0.34 Upper: 0.34 Lower: 0.10 Upper: 0.10 10.9–11.0; Lower: 0.37 Upper: 0.38 Lower: 0.11 Upper: 0.11 12.5–12.7 Lower: 0.45 Upper: 0.01 Lower: 0.13 Upper: 0.01 Exemplar 5 1.6–4.7 N/A N/A 4833.90 N/A N/A https://doi.org/10.1371/journal.pone.0317424.t001