Description: Passive acoustic data provide a prime source of information on marine mammal distribution and behaviour. Particularly in the Southern Ocean, where ship-based data collection can be severely hampered by weather and ice conditions, passive acoustic monitoring (PAM) of marine mammals forms an important source of year-round information on acoustic presence. Array data can be used to obtain directional information on the species present in the recordings to derive movement patterns. Acoustic arrays furthermore allow spatial comparisons of marine mammal distribution patterns and habitat affinities when the acoustic presence information is linked to local environmental parameters. Here we present two passive acoustic monitoring arrays that have been implemented by the Alfred Wegener Institute’s Ocean Acoustic Lab and serve the investigation of marine mammals on different spatial scales. During the austral summer season 2012/2013 a local scale array of sea ice-based time-synchronized passive acoustic recorders was deployed in Atka Bay, Antarctica. The PASATA (PASsive Acoustic Tracking of Antarctic marine mammals) project investigates coastal local habitat usage and communication ranges of marine mammals by integrating positional information from triangulation of calling animals and information from environmental parameters. For studies on marine mammals over larger spatial scales, 23 passive acoustic recorders were deployed in oceanographic moorings in the Southern Ocean, reaching from the Greenwich meridian throughout the Weddell Sea to the Western Antarctic Peninsula. The inter-disciplinary nature of this mooring array allows combining in-situ oceanographic measurements with passive acoustic data on marine mammal occurrence. It furthermore forms the first basin-wide, long term array, at least in the Southern Ocean. Here, we describe both arrays, the recorder types used, and technical and logistic requirements for PAM in a polar environment.

Description: Passive acoustic data provide a prime source of information on marine mammal distribution and behaviour. Particularly in the Southern Ocean, where ship-based data collection can be severely hampered by weather and ice conditions, passive acoustic monitoring (PAM) of marine mammals forms an important source of year-round information on acoustic presence. Array data can be used to obtain directional information on the species present in the recordings to derive movement patterns. Acoustic arrays furthermore allow spatial comparisons of marine mammal distribution patterns and habitat affinities when the acoustic presence information is linked to local environmental parameters. Here we present two passive acoustic monitoring arrays that have been implemented by the Alfred Wegener Institute’s Ocean Acoustic Lab and serve the investigation of marine mammals on different spatial scales. During the austral summer season 2012/2013 a local scale array of sea ice-based time-synchronized passive acoustic recorders was deployed in Atka Bay, Antarctica. The PASATA (PASsive Acoustic Tracking of Antarctic marine mammals) project investigates coastal local habitat usage and communication ranges of marine mammals by integrating positional information from triangulation of calling animals and information from environmental parameters. For studies on marine mammals over larger spatial scales, 23 passive acoustic recorders were deployed in oceanographic moorings in the Southern Ocean, reaching from the Greenwich meridian throughout the Weddell Sea to the Western Antarctic Peninsula. The inter-disciplinary nature of this mooring array allows combining in-situ oceanographic measurements with passive acoustic data on marine mammal occurrence. It furthermore forms the first basin-wide, long term array, at least in the Southern Ocean. Here, we describe both arrays, the recorder types used, and technical and logistic requirements for PAM in a polar environment.

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: The recent identification of the bio-duck call as Antarctic minke whale (AMW) vocalization allows the use of passive acoustic monitoring to retrospectively investigate year-round spatial-temporal patterns in minke whale occurrence in ice-covered areas. Here, we present an analysis of AMW occurrence patterns based on a 9-year passive acoustic dataset (2008–2016) from 21 locations throughout the Atlantic sector of the Southern Ocean (Weddell Sea). AMWs were detected acoustically at all mooring locations from May to December, with the highest presence between August and November (bio-duck calls present at more than 80% of days). At the southernmost recording locations, the bio-duck call was present up to 10 months of the year. Substantial inter-annual variation in the seasonality of vocal activity correlated to variation in local ice concentration. Our analysis indicates that part of the AMW population stays in the Weddell Sea during austral winter. The period with the highest acoustic presence in the Weddell Sea (September–October) coincides with the timing of the breeding season of AMW in lower latitudes. The bio-duck call could therefore play a role in mating, although other behavioural functions of the call cannot be excluded to date.

Description: Bowhead whales (Balaena mysticetus) of the East Greenland-Svalbard-Barents Sea (Spitsbergen) population have been depleted close to the point of extinction by commercial whaling and are still considered as endangered. Due to their low abundance and the remoteness of their habitat, baseline knowledge on spatio-temporal distribution patterns and behavioural aspects are scarce, yet crucial for the conservation of this population. Long-term passive acoustic recordings were collected at different locations in eastern Fram Strait (78-79°N, 0-7°E) as part of the Ocean Observing System FRAM (Frontiers in Arctic Marine Monitoring). Data recorded in 2012 and 2016/2017 were analysed for the acoustic occurrence of bowhead whales at an hourly resolution using an automated detector. Bowhead whales were acoustically present from autumn throughout the winter months (October-February) and occasionally in spring (March-June), supporting hypotheses that Fram Strait is an important overwintering area. Acoustic presence peaked between mid-November and mid-December when bowhead whales were recorded almost daily, often hourly for several days in a row. The observed peak in acoustic presence coincided with the presumed mating period of bowhead whales, starting in late winter, indicating that Fram Strait may also serve as a mating area. Detailed analyses of recordings of a single year and location revealed eight distinct bowhead whale song types comprising simple songs and call sequences. No bowhead whales were recorded in summer (July-September), indicating that they either were vocally inactive or had migrated to summering areas. Compared to previous studies in western Fram Strait, bowhead whale detections in our recordings were less frequent and less complex. The observed regional differences in bowhead whale acoustic behaviour across Fram Strait suggest that our mooring locations in eastern Fram Strait may represent the eastern distribution boundary of the bowhead whale overwintering area.

Description: In 2009 scientists at the Alfred Wegener Institute (AWI) Helmholtz Centre of Polar and Marine Research in Bremerhaven established the PEBCAO-group. Since then the group is investigating the “Plankton Ecology and Biogeochemistry in the Changing Arctic Ocean” in a uniquely synchronized approach. This involves the integration of molecular genetic investigations with traditional plankton investigations, optical parameters, microbiology, work on key species (e.g. Phaeocystis sp. or Calanus sp.), and finally the composition of organic matter. The work is carried out in the Central Arctic Ocean and the Fram Strait, where it is complementing a monitoring program on phytoplankton and vertical particle flux that has been carried out along ~79°N and in the AWI HAUSGARTEN for more than ten years. This is done in cooperation with oceanographers and deep-sea biologists. Combining the long-term data (1998-2012) with the integrative approach of PEBCAO we revealed a trend towards slightly higher chlorophyll a in the WSC during summer that is accompanied by a shift from diatoms to Phaeocystis sp. and other small pico- and nanoplankton. Furthermore, a clear zonation in the waters of the East Greenland Current (EGC), the West Spitsbergen Current (WSC) as well as for the mixing zone of both (MW) was identified in all parameters. The PEBCAO approach is an example for a successful and synergistic integration of molecular biodiversity studies with classical approaches of biological oceanography.

Description: Although Antarctic blue whales (Balaenoptera musculus intermedia) are known to occur throughout the Southern Ocean, undertaking seasonal migrations between their breeding and feeding grounds, knowledge on spatio-temporal patterns in their distribution is limited. Here, passive acoustic recordings collected over three years from four locations at different latitudes along the Greenwich meridian south of 59°S, provided data on patterns in occurrence of stereotyped 3-unit vocalizations of Antarctic blue whales in the Weddell Sea. Highest vocalization rates occurred during austral summer at all recording locations, with calls detectable during 10 months in recordings from 59°S and 66°S, over 11 months in recordings from 69°S and year-round in recordings from coastal waters off the Antarctic continent at 70°S. Antarctic blue whale acoustic activity showed seasonal maxima that differed in timing between recorders, but were consistently present between years. Onset of increased acoustic presence occurred in November-December in the northernmost recorder at 59°S, in January in the recorders at 66°S and 69°S and in February in the southernmost recorder at 70°S. These results are consistent with a southbound migration of vocalizing Antarctic blue whales with at least some individuals migrating as far south as the Antarctic coastal waters during austral summer. A secondary increase in acoustic activity occurred during March and April in the recorders at 59°S and 66°S, respectively, supporting previous suggestions that migration of Antarctic blue whales is segregated in time. The absence of a corresponding secondary maximum at 69°S hints towards not all individuals migrating this far south, and that migratory destinations (or alternatively, vocal activity) may hence be spatially segregated. The year-round presence of Antarctic blue whale calls off the Antarctic continent suggests that Antarcticas’ coastal polynyas, i.e. patches of open water where animals can surface to breathe, may provide important habitats for animals to overwinter in high latitude waters.