What’s all that racket! Soundscapes, phenology, and biodiversity in estuaries

Soundscape phenology Based on six years of data recorded at three stations, we examined the phenology of acoustic activ- ity of snapping shrimp (as a measure of high frequency SPL) and fish (as a measure of low fre- quency SPL) by detecting the date of the first abrupt change in SPL (i.e. posterior probability or PP � 0.5). We calculated the first abrupt change for both data sets (i.e. one with all sounds and noise, and the data set that excluded physical sounds and anthropogenic noise) but report exact dates from the pure biological dataset (Fig 3; S3 and S4 Tables; S5–S13 Figs). In spring recordings at station 9M, we found the first peak in high frequency SPL to occur on April 9, April 3, April 1, March 25, March 23, and March 29 in 2013, 2014, 2015, 2016, 2017, and 2018, respectively (S3 Table; S2 and S5 Figs). At the same station, we detected the first peak in low frequency SPL to occur on April 2, March 27, April 6, March 25, March 25, and March 28 in 2013, 2014, 2015, 2016, 2017, and 2018, respectively (S4 Table; S3 and S6 Figs). Similar patterns were found at sta- tions 14M and 37M (S3 and S4 Tables). We found that in years with higher mean spring water temperatures, the first peak in high, low, and broadband SPL occurred earlier as compared to years with lower mean spring water temperatures (Fig 3A–3C). During the spring of 2017, an increase in acoustic activity of snapping shrimp was detected 8 days earlier than the 6-year average at station 9M (S3 Table). At the same station, during spring of 2017, acoustic activity of soniferous

fish was detected 4 days earlier than the 6-year average (S4 Table). Mean water temperature Fig 2. Time series of low frequency Sound Pressure Levels (SPLs) from 2013 until 2018. Heat maps represent temporal and spatial patterns of low (i.e. 50–1200 Hz) frequency SPLs reflecting fish and lower frequency range of snapping shrimp acoustic activity at stations (A) 9M, (B) 14M, and (C) 37M in the May River, SC. Time is shown between noon and noon of the next day. Gaps in data = white, temperature = black line, and daylight hours = dotted line. Green dots indicate first posterior probability (PP) of change � 0.5 detected during springtime. At station (C) 37M first PP was not calculated for spring 2017 due to missing acoustic data. This dataset contained files with physical sounds and anthropogenic noise. https://doi.org/10.1371/journal.pone.0236874.g002 PLOS ONE Estuarine soundscapes and biodiversity PLOS ONE | https://doi.org/10.1371/journal.pone.0236874 September 3, 2020 4 / 18