Passive acoustic listening stations (PALS) show rapid onset of ecological effects of harmful algal blooms in real time

Abstract

Monitoring ecological changes in marine ecosystems is expensive and time-consuming. Passive acoustic methods provide continuous monitoring of soniferous species, are relatively inexpensive, and can be integrated into a larger network to provide enhanced spatial and temporal coverage of ecological events. We demonstrate how these methods can be used to detect changes in fish populations in response to a Karenia brevis red tide harmful algal bloom by examining sound spectrum levels recorded by two land-based passive acoustic listening stations (PALS) deployed in Sarasota Bay, Florida, before and during a red tide event. Significant and temporally persistent decreases in sound spectrum levels were recorded in real time at both PALS in four frequency bands spanning 0.172–20 kHz after K. brevis cells were opportunistically sampled near the stations. The decrease in sound spectrum levels and increase in K. brevis cell concentrations also coincided with decreased catch per unit effort (CPUE) and species density per unit effort (SDPUE) data for non-clupeid fish and soniferous fish species, as well as increased reports of marine mammal mortalities in the region. These findings demonstrate how PALS can detect and report in real time ecological changes from episodic disturbances, such as harmful algal blooms.

Effects of Multiple Karenia brevis Red Tide Blooms on a Common Bottlenose Dolphin (Tursiops truncatus) Prey Fish Assemblage: Patterns of Resistance and Resilience in Sarasota Bay, Florida

“…The combination of decreases in prey assemblage abundance, species density, and Shannon diversity at fish sampling stations during ichthyotoxic conditions in the summer months suggests K. brevis had a severe effect on dolphin prey populations. Work by Rycyk et al (2020) in the Sarasota Bay region supports these findings. Using passive acoustic techniques and data from SDRP's fish monitoring program, Rycyk et al (2020) documented a sudden decrease in mean sound spectrum levels in 2018 (June 2018 to October 2018), coincident with decreased non-clupeid and soniferous (i.e., noise-making) fish abundances, decreased fish species density, and increased observations of K. brevis in the Sarasota Bay region.…”

“…Work by Rycyk et al (2020) in the Sarasota Bay region supports these findings. Using passive acoustic techniques and data from SDRP's fish monitoring program, Rycyk et al (2020) documented a sudden decrease in mean sound spectrum levels in 2018 (June 2018 to October 2018), coincident with decreased non-clupeid and soniferous (i.e., noise-making) fish abundances, decreased fish species density, and increased observations of K. brevis in the Sarasota Bay region. In the winter months, results were less conclusive.…”

Initial estuarine response to the nutrient-rich Piney Point release into Tampa Bay, Florida

“…Prior blooms in Tampa Bay were more localized and K. brevis was at lower abundances in comparison to the 2021 bloom event, potentially mitigating exposure of fishes to related harmful conditions. In Sarasota Bay to the south, fish activity measured by passive acoustic methods was significantly lower during a 2018 red tide event as compared to pre-bloom levels (Rycyk et al, 2020).…”

The influence of variations in background noise on Florida manatee (Trichechus manatus latirostris) detection of boat noise and vocalizations

“…Sound clips were successfully recorded and stored 94% of the time. For more information about the acoustic recording setup, see Rycyk et al (2020) [ 34 ]. Data were used from a contiguous two-week period in winter (January or February, 2019 or 2020) and a contiguous two-week period in summer (August, 2019 or 2020) from each location.…”