Details

Autor(en) / Beteiligte

• Freeman, Simon E.
• Freeman, Lauren
• Giorli, Giacomo
• Haas, Andreas F.

Titel

Acoustic emissions by marine algae during photosynthesis

Ist Teil von

• The Journal of the Acoustical Society of America, 2018-03, Vol.143 (3), p.1796-1796

Erscheinungsjahr

2018

Quelle

AIP Journals Complete

Beschreibungen/Notizen

• Coastal underwater soundscapes typically contain signals from soniferous, biological processes. Identifying the sources that contribute to oftentimes acoustically complex soundscapes would facilitate a noninvasive, remote, and volumetrically integrative method to survey underwater ecological state, as has been demonstrated on land. To date the lack of knowledge on these sources has posed a challenge for extracting meaningful ecological information from underwater biological soundscape recordings. We have observed that photosynthesis by macroalgae is an acoustically active process, driven by oxygen bubbles separating from the algal surface and ringing at the Minnaert frequency. The resultant soundscapes correlate with benthic macroalgal cover across ecological gradients on shallow Hawaiian reefs during periods of daylight. Bubble size, production rate, and sound exposure level follow the concentration of dissolved oxygen, which in turn rises and falls with the availability of photosynthetically active radiation. Increased macroalgal cover results from climate related stress, overfishing and/or pollution through nutrient runoff and serves as an indicator of degradation in many underwater ecosystems. Our observation lays the foundation for signal processing methods that quickly and passively evaluate relative algal abundance in littoral waters. These findings can also be applied towards more accurate monitoring of primary production in industrial processes.