ALBERT

Description: Passive acoustic monitoring (PAM) data were collected by recorder SV1009 of type Sono.Vault (manufactured by develogic GmbH, Hamburg, Germany) at 65°41.79' S, 36°41.012' W, mooring AWI208-8, in Weddell Sea, Atlantic sector of the Southern Ocean. During a deployment period from January 2017 to January 2019, passive acoustic data were collected from January 2017 to May 2018 (recording period) by SV1009 as part of the Hybrid Antarctic Float Observing System (HAFOS) in the Weddell Sea. The recorder was moored at 1032 m depth and scheduled to record continuously at a sample rate of 6,857 Hz. Further details about the data acquisition and processing of this data set can be found in the accompanying metadata file (see Additional metadata) as well as the data processing report (see Data Processing Report). Further information on terminology, data processing, preparation and standardization can be found in the associated Standard Operating Procedure (SOP) Glossary (Thomisch et al. 2023a) and SOP Part 1: Data preparation and standardization (Thomisch et al. 2023b).

Description: This study investigates the relevance of the Elephant Island (EI) region for Southern Hemisphere fin whales (Balaenoptera physalus) in their annual life cycle. We collected 3 years of passive acoustic recordings (January 2013 to February 2016) northwest of EI to calculate time series of fin whale acoustic indices, daily acoustic occurrence, spectrograms, as well as the abundance of their 20-Hz pulses. Acoustic backscatter strength, sea ice concentration and chlorophyll-a composites provided concurrent environmental information for graphic comparisons. Acoustic interannual, seasonal and diel patterns together with visual information and literature resources were used to define the period of occupancy and to infer potential drivers for their behaviour. Spectral results suggest that these fin whales migrate annually to and from offshore central Chile. Acoustic data and visual information reveal their arrival at EI in December to feed without producing their typical 20-Hz pulse. For all 3 years, acoustic activity commences in February, peaks in May and decreases in August, in phase with the onset of their breeding season. Our results emphasize the importance of EI for fin whales throughout most of the year. Our recommendation is to consider EI for establishing a marine protected area to expedite the recovery of this vulnerable species.

Description: To develop reliable and effective management and conservation strategies for marine mammals, a profound knowledge about their distribution, as well as on the location of key habitats are essential. The waters off Elephant Island (Antarctica) are thought to serve as a feeding ground for baleen whales; however, detailed long-term information on patterns in the distribution of marine mammals in this area is still lacking for many species. This study aimed to investigate i) the acoustic biodiversity, as well as ii) inter-annual patterns, and iii) intra-annual patterns in the acoustic presence of marine mammals off Elephant Island. For this purpose, passive acoustic data collected here from January 2013 to February 2016 were analyzed both visually (in the form of spectrograms) and aurally for the presence of marine mammal vocalizations. Daily acoustic presence of marine mammals was assessed based on species-specific vocal signatures. During the overall recording period, eight marine mammal species were identified: Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (B. physalus), Antarctic minke (B. bonaerensis) whales, humpback whales (Megaptera novaeanglia), Killer whales (Orcinus orca), sperm whales (Physeter macrocephalus), Leopard seals (Hydrurga leptonyx) and crabeater seals (Lobodon carcinophaga). For some species, a temporal pattern in the acoustic presence was detected, whereas other species did not exhibit a temporal pattern in their acoustic presence, but were acoustically present either year-round or rather occasionally. Antarctic minke whales were acoustically present from June to September and absent during austral summer, indicating that their acoustic presence was linked to the formation of sea-ice. Furthermore, the annual number of days with Antarctic minke whale calls declined from 2013 to 2015, which might possibly be linked to an inter-annual decrease in the sea-ice extent off Elephant Island. The amount of days with killer whale vocalizations peaked during austral winter when the amount of days with Antarctic minke whale vocalizations reached its maximum, indicating a possible link between killer whale acoustic presence and the availability of their prey (Antarctic minke whales, amongst others). Vocalizations of both seal species occurred primarily during austral winter and spring, i.e. from September to December for leopard seals and during September and October for crabeater seals, which is in accordance with their breeding period and suggests that both species were breeding off Elephant Island. Besides, vocalizations of all four baleen whale species were detected during austral winter, possibly indicating that part of the populations remained in the Southern Ocean year-round. Hence, this study adds further evidence for the hypothesis of a complex migratory behavior of baleen whales. Overall, this study suggests that the Elephant Island region serves as an important feeding and breeding habitat for several marine mammal species either year-round or seasonally. The identification of such ecologically important areas with high (acoustic) biodiversity can considerably benefit future conservation applications, such as the designation of marine protected areas.

Description: Summertime visual observations suggest that the region around Elephant Island may serve as an important feeding area for fin whales. To explore its year-round relevance, passive acoustic recordings collected northwest of Elephant Island (61°0.88’S, 55°58.53’W) from January 2013 to February 2016 were analysed for seasonal and diel patterns of fin whale 20 Hz calls. Calls were detected year-round, although in some years calls were not present during all months. For all years, fin whale calls were consistently present from March to July for more than 90% of days per month. From August to January, percentage of days with calls varied between years, with presence exceeding 75% of days per month throughout 2014, whereas in 2015 calls were absent in October and November. In 2013, fin whale calling dropped in August and increased again towards October and November. Quantitative analyses of power spectral density for the 20-Hz and 89-Hz fin whale bands, showed that fin whale acoustic power in both frequency bands followed a Gaussian-like temporal pattern, increasing in late January, peaking during April-May and decreasing in late August for all years. A second shoulder peak in PSD seemed to occur during the second part of July showing strongest for the upper fin whale band, followed by a rapid decrease, after which SNR for both bands dropped to zero. Diel patterns in call activity were analysed for a 10-month subset of the data from 2013. Fluctuations in call rates did not follow a diel pattern nor correspond to local insolation. The observed peaks in fin whale call activity correspond to the periods during which fin whale super groups have been observed visually in this region. Our year-round acoustic analysis indicates that the Elephant Island region likely carries an important role for fin whales throughout the entire year.

Description: Here we present a comprehensive description of the acoustic environment approximately 31 km west-northwest of Minstrel Point, Elephant Island, Antarctica at 210 m water depth based on three years (Jan 2013 – Feb 2016) of subsampled (5 min per hour) passive acoustic recordings. Long-term spectrograms reveal a notable recurrence of acoustic environments between years. Fin and Antarctic blue whale calls dominate the low (〈 100 Hz) part of the biophonic spectrum energetically from end of January to late July/early August. November through early January are dominated by leopard seal vocalizations at around 300 Hz. Concurrently, the geophonic spectrum exhibits strong fluctuations between days, both due to storm and tidal influences, causing flow and shackle noise from the instrumentation itself. Manual analysis of every second day of the subsampled data by visual and aural screening (employing short term spectrograms) was used to examine the data in greater detail for additional acoustic contributions and to assign the various acoustic signatures to their sources. Six cetacean and two pinniped species were identified based on their acoustic signatures and analysed for seasonal and diel patterns in occurrence. Anthrophonic signatures were attributed to air guns on 3 % of the analysed days. Vessel noise was noted between 10 and 12% of days on annual averages, occurring mainly in austral summer and fall with sporadic events throughout the remainder of the year.

Description: Here we present a comprehensive description of the acoustic environment approximately 31 km west-northwest of Minstrel Point, Elephant Island, Antarctica at 210 m water depth based on three years (Jan 2013 – Feb 2016) of subsampled (5 min per hour) passive acoustic recordings. Long-term spectrograms reveal a notable recurrence of acoustic environments between years. Fin and Antarctic blue whale calls dominate the low (〈 100 Hz) part of the biophonic spectrum energetically from end of January to late July/early August. November through early January are dominated by leopard seal vocalizations at around 300 Hz. Concurrently, the geophonic spectrum exhibits strong fluctuations between days, both due to storm and tidal influences, causing flow and shackle noise from the instrumentation itself. Manual analysis of every second day of the subsampled data by visual and aural screening (employing short term spectrograms) was used to examine the data in greater detail for additional acoustic contributions and to assign the various acoustic signatures to their sources. Six cetacean and two pinniped species were identified based on their acoustic signatures and analysed for seasonal and diel patterns in occurrence. Anthrophonic signatures were attributed to air guns on 3 % of the analysed days. Vessel noise was noted between 10 and 12 % of days on annual averages, occurring mainly in austral summer and fall with sporadic events throughout the remainder of the year. This work illustrates the value of soundscape studies and provides a first step towards understanding the actual contribution of sound sources in their respective acoustic context and overall local noise budget.

Description: Recent visual observations suggest that the region around Elephant Island serves as an important feeding area for fin whales. Passive acoustic recordings collected northwest of Elephant Island (61°0.88’S, 55°58.53’W) from January 2013 to February 2016 were analysed manually for seasonal and diel patterns of fin whale 20 Hz calls. Overall, calls were detected year-round, although in some years calls were not present during all months. For all years, fin whale calls were consistently present from February to July for more than 90% of days per month. From August to January, percentage of days with calls varied between years, with presence exceeding 75% of days per month throughout 2014, whereas in 2015 calls were absent in October and November. In 2013, fin whale calling dropped in August and increased again towards November (present 80% of days per month). Diel patterns in call activity were analysed for a 10-month subset of the data from 2013. Fluctuations in call rates did not follow a diel pattern nor correspond to local insolation. During peak calling period, maximum calls amounted approximately to 80 per 10-minute file. Fluctuations in call presence outside the peak calling period may be explained by variation in local ice conditions as drift may temporally force the animals away to areas with reduced ice concentrations. Furthermore, delays in the timing of migration between age groups, sexes and/or reproductive classes may also affect temporal patterns in the clustering of calls. The observed peaks in fin whale call activity correspond to the periods during which fin whale super groups have been repeatedly observed visually in this region. Our year-round acoustic analysis indicates that the Elephant Island region is likely to play an important role for fin whales throughout the remainder of the year.