Department of Oceanography, National Sun Yat-Sen University, Kaohsiung, Taiwan.
University Malaysia Sarawak, Institute of Biodiversity and Environmental Conservation, Sarawak, Malaysia.
PeerJ. 2024 Sep 26;12:e18114. doi: 10.7717/peerj.18114. eCollection 2024.
Oxygen bubbles that leak from seagrass blades during photosynthesis have been hypothesized to cause cavitation sounds in aquatic plants. Here we investigate low-amplitude sounds with regular pulse rates produced during photosynthesis in seagrass beds of (Qitou Bay, Penghu islands and Cigu Lagoon, Taiwan). Sound pulses appear in the morning when illumination exceeds 10,000 Lux, peak at midday and decrease in midafternoon on a sunny day. Frequencies peak between 1 to 4 kHz, durations range between ca. 1.8 to 4.8 ms, and sound pressure level 1 cm from the bed is 105.4 ± 0.5 dB re 1 μPa (1100 h on a cloudy day). Sounds attenuate rapidly with distance, disappearing beyond 15 cm. Blocking sunlight or administering herbicide stops ongoing sounds. Gas bubbles are not typically seen during sound production ruling out cavitation, and external force (scissor cutting or plant pressed against the substrate) applied to the patch, leaves, petioles, or rhizomes generally increases pulse rate. We suggest sound emission is caused by internal oxygen transport through pores in diaphragms (a whistle mechanism) at the leaf base and nodes of the rhizome.
光合作用过程中从海草叶片逸出的氧气泡被假设会引起水生植物的空化噪声。在这里，我们研究了澎湖七美湾和台湾七股泻湖海草床在光合作用过程中产生的振幅较低、脉冲率规则的声音。当光照强度超过 10,000 Lux 时，声音脉冲会在早晨出现，中午达到峰值，并在晴天的午后逐渐减少。频率峰值在 1 到 4 kHz 之间，持续时间约为 1.8 到 4.8 ms，距离床 1 厘米处的声压级为 105.4 ± 0.5 dB 重 1 μPa（阴天 1100 h）。声音随距离迅速衰减，超出 15 厘米后消失。遮挡阳光或施用药剂会阻止正在进行的声音。在产生声音时通常看不到气泡，排除了空化的可能性，并且施加到斑块、叶片、叶柄或根茎上的外力（剪刀切割或植物压在基质上）通常会增加脉冲率。我们认为声音的产生是由于内部氧气通过叶片基部和根茎节点上的隔膜（哨子机制）中的孔隙进行运输所致。
