PS 51-180 - A comparative study of the daily variation in the underwater acoustic diversity between urban and rural tropical streams in Puerto Rico

Background/Question/Methods

Riverine bioacoustics is a relatively new area of research with great utility in environmental and ecological studies. This line of research generates essential data useful for conservation and monitoring initiatives for rivers and other water bodies’ biodiversity. This study presents a preliminary quantitative assessment of the daily variation in the underwater acoustic diversity between rural and urban tropical streams. We selected four tropical streams (two urban and two rural) in the Puerto Rico watersheds of Río Grande de Manatí, Río La Plata and the Río Grande de Loíza, specifically the rural streams Río Emajagua (EMA), Río Toro Negro (TNG), and the urban streams Río Grande de Loíza (GLZ) and Río Bucarabones (BUC). Two hydrophones were placed at each stream for 24 continuous hours per week for three weeks. The first minute of each hour was selected to form a subsample of 24m per day of frequencies between 0 to 22kHz. The subsamples were then analyzed for their Acoustic Complexity Index (ACI) and Acoustic Diversity Index (ADI) using the R packages seewave and sounecology.

Results/Conclusions

Through the acoustic analyses, the most significant difference in sound diversity was found at the BUC, recording less than 2.5 different sound types from 3:00 to 11:00 and less than 1.5 ADI from 12:00 to 1:00, a relatively substantial decrease from the average of 2.89 ADI from the other three streams. We can conclude that the daily time with less activity in all the streams is between 11:00 to 17:00. In contrast, the periods with a higher and more constant acoustic activity were between 2:00 to 9:00 and 18:00 to 23:00 in both rural and urban systems. These results are helpful for future underwater bioacoustics monitoring studies since they show at which time during a 24 h period, there is a richer acoustic activity in urban and rural streams on the Island.