Dataset: Passive acoustic data from Galapagos rocky subtidal

Name: Sound pressure levels from hydrophone recordings at six sites in the Galapagos Islands from September 2020 through August 2022 to examine soundscapes during the Anthropause and beyond
Published: 2023-09-13
Keywords: Galapagos, passive acoustics, Eastern Tropical Pacific, soundscape, rocky subtidal, biota, oceans

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Spatial Extent: N:-0.235038 E:-90.14065 S:-1.32879 W:-90.38498

Temporal Extent: 2020-09 - 2022-08

Project:

RAPID: Illuminating the effects of a COVID-19 elimination of diver disturbance on reef fish behavior, distribution and ecosystem functioning in the Galapagos Marine Reserve (Galapagos diver disturbance)

Principal Investigator:

Jon D. Witman (Brown University)

Scientist:

Robert Lamb (Brown University)

Franz Smith (Brown University)

Contact:

Jon D. Witman (Brown University)

BCO-DMO Data Manager:

Dana Stuart Gerlach (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Sawyer Newman (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2023-09-13

Restricted:

Validated:

Current State:

Preliminary and in progress

Sound pressure levels from hydrophone recordings at six sites in the Galapagos Islands from September 2020 through August 2022 to examine soundscapes during the Anthropause and beyond

Abstract:

These are passive acoustic data sampled with SoundTrap 300 hydrophones at 10-15 meters depth at 6 sites in the Galapagos Islands from September 2020 through August 2022. Data represent median Sound Pressure Levels (SPLs) in 15 minute bins measured for a minimum of 24 hours per site. These data are part of a larger project to understand the effect of the reduction of scuba diver disturbance during the COVID-19 lockdown (the "Anthropause") on the biological soundscape as well as effects on behavioral interactions among fish.

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Methods & Sampling

Sampling and analytical procedures:

Approximately 1900 hours of underwater sound was sampled by SoundTrap 300 hydrophones during the study period from September 2020 through August 2022. The hydrophones were set to record at 98 hertz (hz) to record continuously over the duration of the deployment to capture acoustic signals in the soundscape including biological (fish, snapping shrimp, sea lions, etc.) and anthropogenic (divers, boat noise) sound.

A standard procedure was followed to deploy hydrophones at 3 sites of high (Champion, Gordon, Seymour) and low (Gardner, Baltra, Daphne Menor) diver disturbance during the “Anthropause” when tourism was substantially reduced in 2020 due to the COVID quarantine. Hydrophone were deployed again at the same locations in 2021 and 2022 as tourism increased. At each of the six sites, a single hydrophone was mounted on a stainless steel stand so that it was positioned vertically about 1.5 meters about the rocky bottom (~10-15 m depth). This was done by scuba diving from a small (14 m long) sport fishing type boat (MV Valeska out of Puerto Ayora). The acoustic recordings were made simultaneously at two sites for 2 to 8 days and the procedure was repeated so all 6 sites were sampled.

The 2020 data can serve as a baseline of the total amounts of biological and anthropogenic noise in the Galapagos during the Anthropause, and can be compared to 2021 and 2022 data after the COVID 19 quarantine ended and activities resumed. Biological soundscape differences between day and night can also be analyzed using the local time (Galapagos Island Time of UTC minus 6 hours).

Data Processing Description

Deployment records were cleaned in Raven Pro version 1.6 software to remove the sound of divers setting up the hydrophone stand. The resultant filtered WAV files were converted into statistical metrics with the use of Matlab-based acoustic processing package Triton (version 1.93) from Scripps Institution of Oceanography. Both the standard package and soundscape metrics "remora” were utilized to convert WAV files into full spectrogram files.

Triton, Raven, and R Studio software were used to compute and visualize sound pressure levels. Sound pressure levels for the full broadband and low frequency band were computed to isolate fish vocalization. Mean and median sound metrics were computed in both frequency bands at 15-minute and 30 second intervals. Median sound pressure levels across the broadband using 15-minute intervals offers a general coarse grain profile of the soundscape. This process created 15,800 usable sampling windows total.

Raven Pro version 1.6 software (https://ravensoundsoftware.com/software/raven-pro/)
Triton Software version 1.93 (https://www.cetus.ucsd.edu/technologies_triton.html)

BCO-DMO Processing

- Merged individual data tables for each site sampled in 2020 into a single data table (Baltra Anthropause Oct1-2 2020.xlsx, Champion Anthropause Sept 23 2020.xlsx, Daphne Menor Anthropause Oct17-18 2020.xlsx, Gardner Anthropause Oct20-21 2020.xlsx, Gordon Anthropause Oct 16 2020.xlsx, Seymour Anthropause Oct 10 2020.xlsx)
- Concatenated data from 2021 and 2022 to the 2020 data (WitmanAcoustic2021-01.xlsx and WitmanAcoustic2022-08.xlsx)
- Joined site location information (latitude and longitude) provided by PI to main data table
- Created a datetime column in ISO8601 format (UTC time zone)
- Removed blank spaces from column header names
- Kept separate local date and local time columns to allow analysis of day-night differences in biological soundscape, but changed date format to YYYY-MM-DD
- Sorted chronologically by site

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-2035354

Deployments

None available yet

Instruments

Hydrophone

Supplied Name: SoundTrap 300 STD Compact recorders

Supplied Description:

A single SoundTrap 300 hydrophone was mounted on a stainless steel stand vertically about 1 meter above the rocky bottom with . The hydrophone was set to record continuously at 98 hz.

For instrument specs see: http://www.oceaninstruments.co.nz/product/soundtrap-300-std

Instrument Type

Generic Name: Hydrophone

Generic Description:

A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change.

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
ISO_DateTime_UTC	Sample Datetime in ISO8601 format Format: %Y-%m-%dT%H:%M:%SZ	unitless	ISO_DateTime_UTC
Latitude	Latitude of sampling location	decimal degrees	lat
Longitude	Longitude of sampling location	decimal degrees	lon
Site	Study Site	unitless	site
Sound_Pressure_Level	Sound Pressure Level	decibels referenced to 1 microPascal (db re 1 uPa)	sound_press
Sample_Date_local	Sample date (Galapagos local timezone of UTC-6) Format: %Y-%m-%d	unitless	date_local
Sample_Time_local	Sample time (Galapagos local timezone of UTC-6) Format: %H:%M:%S	unitless	time_local

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Database

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Dataset: Passive acoustic data from Galapagos rocky subtidal