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

One striking pattern that we observed was in the seasonal fluctuations of SPLs, which increased and decreased with the seasonal temperature changes of the estuary (Figs 1 and 2 and S1 Fig). These patterns (and the results presented below) were preserved even when files with physical sounds and anthropogenic noise were removed, indicating that the sound pat- terns were biological in nature (S2–S4 Figs). With an increase of water temperature for every 0.5˚C, 0.6˚C, and 0.8˚C during the springtime, we detected a corresponding increase of 1 dB in SPL for high, low, and broadband frequencies, respectively. Higher values of SPLs were present in the summer months as compared to lower values in the winter, early spring, and late fall (Figs 1 and 2 and S1–S4 Figs). We observed significant differences in SPLs among years for all examined frequency ranges (p < 0.05). The highest SPL values occurred in 2013 and 2014, the lowest in 2016 and 2017. In addition, snapping shrimp acoustic activity (i.e. mea- sured as SPLs in the high frequency bandwidth of 7,000–40,000 Hz) was higher during the day, low tide, and new moon as compared to the night, high tide, and full moon (p < 0.05). SPLs within the low frequency band were higher during the night (i.e. associated with fish cho- rusing) and followed an oscillating pattern associated with the lunar phase with higher values recorded on the first quarter of the lunar phase (p < 0.05). Values in the broadband SPL fre- quency range, which reflected a combination of all biological sounds, were the highest during

the night, new moon and falling tide (p < 0.05). Fig 1. Time series of high frequency Sound Pressure Levels (SPL) from 2013 to 2018. Heat maps represent temporal and spatial patterns of high (i.e. 7000–40,000 Hz) frequency SPLs reflecting 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.g001 PLOS ONE Estuarine soundscapes and biodiversity PLOS ONE | https://doi.org/10.1371/journal.pone.0236874 September 3, 2020 3 / 18