Description: Distribution and movement patterns of Antarctic blue whales Balaenoptera musculus intermedia at large temporal and spatial scales are still poorly understood. The objective of this study was to explore spatio-temporal distribution patterns of Antarctic blue whales in the Atlantic sector of the Southern Ocean, using passive acoustic monitoring data. Multi-year data were collected between 2008 and 2013 by 11 recorders deployed in the Weddell Sea and along the Greenwich meridian. Antarctic blue whale Z-calls were detected via spectrogram cross-correlation. A Blue Whale Index was developed to quantify the proportion of time during which acoustic energy from Antarctic blue whales dominated over background noise. Our results show that Antarctic blue whales were acoustically present year-round, with most call detections between January and April. During austral summer, the number of detected calls peaked synchronously throughout the study area in most years, and hence, no directed meridional movement pattern was detectable. During austral winter, vocalizations were recorded at latitudes as high as 69°S, with sea ice cover exceeding 90%, suggesting that some Antarctic blue whales overwinter in Antarctic waters. Polynyas likely serve as an important habitat for baleen whales during austral winter, providing food and reliable access to open water for breathing. Overall, our results support increasing evidence of a complex and non-obligatory migratory behavior of Antarctic blue whales, potentially involving temporally and spatially dynamic migration routes and destinations, as well as variable timing of migration to and from the feeding grounds.

Description: Antarctic minke whales (Baleanoptera bonaerensis) occur in open as well as ice-covered waters throughout the Southern Ocean. Their low visual detectability and ice-associated habitat makes the species difficult to study using traditional visual methods. The recent identification of vocalizations produced by Antarctic minke whales now allows the use of passive acoustic records to investigate spatio-temporal patterns in occurrence, also in areas that are (seasonally) inaccessible to ships due to extensive ice cover. Here we present preliminary results on Antarctic minke whale occurrence patterns based on part of a multi-year passive acoustic data set collected from 6 locations throughout the Atlantic sector of the Southern Ocean. These comprised four autonomous passive acoustic recorders which collected data along the Greenwich meridian between 2008 and 2011, one passive acoustic recorder in the Weddell Sea that collected data between 2010 and 2012 and long-term recordings from the PALAOA observatory on the Eckström Iceshelf off the Antarctic continent (2006-2016). Analyses were based on daily presence of Antarctic minke whale pulse trains, also referred to as the bio-duck call. The bio-duck signal is characterized by its repetitive nature, consisting of regular down-sweeped pulses, with most energy located in the 50-300 Hz band. Antarctic minke whales were present at all six Antarctic recording locations from June to December, with highest presence occurring between August and November (〉80% of days with bioduck calls present). At the southernmost recording locations and the location in the Weddell Sea, the bioduck call was present throughout nine and ten months of the year, respectively. Substantial variation in the seasonal on- and offset period of vocal activity of Antarctic minke whales was observed between years at the different recording positions, possibly corresponding to variation in local ice conditions. Ongoing work aims to further quantify this relationship to better understand year-round Antarctic minke whale habitat preferences. Furthermore, further work will comprise more fine-scale analyses to unravel diel patterns in vocal activity and explore if variation in the acoustic signature of the bioduck call can potentially be attributed to regional differences in Antarctic minke whale vocal behavior, possibly representing subpopulations of the species.

Description: Between Greenland and Spitsbergen, Fram Strait is a region where cold ice-covered Polar Water exits the Arctic Ocean with the East Greenland Current (EGC) and warm Atlantic Water enters the Arctic Ocean with the West Spitsbergen Current (WSC). In this compilation, we present two different data sets from plankton ecological observations in Fram Strait: (1) long-term measurements of satellite-derived (1998–2012) and in situ chlorophyll a (chl a) measurements (mainly summer cruises, 1991–2012) plus protist compositions (a station in WSC, eight summer cruises, 1998–2011); and (2) short-term measurements of a multidisciplinary approach that includes traditional plankton investigations, remote sensing, zooplankton, microbiological and molecular studies, and biogeochemical analyses carried out during two expeditions in June/July in the years 2010 and 2011. Both summer satellite-derived and in situ chl a concentrations showed slight trends towards higher values in the WSC since 1998 and 1991, respectively. In contrast, no trends were visible in the EGC. The protist composition in the WSC showed differences for the summer months: a dominance of diatoms was replaced by a dominance of Phaeocystis pouchetii and other small pico- and nanoplankton species. The observed differences in eastern Fram Strait were partially due to a warm anomaly in the WSC. Although changes associated with warmer water temperatures were observed, further long-term investigations are needed to distinguish between natural variability and climate change in Fram Strait. Results of two summer studies in 2010 and 2011 revealed the variability in plankton ecology in Fram Strait.

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: Zooplankton species, which link primary production and higher trophic levels and play a major role in pelagic marine ecosystems, are associated with distinct water masses. In Fram Strait, the only deep-water connection between the Atlantic and Arctic Ocean, relatively warm Atlantic water (AW) enters the Arctic with the West Spitsbergen Current, whereas the East Greenland Current carries cold polar water masses southwards. Rising water temperatures might change the zooplankton community, with possible consequences for the food web. We therefore investigated the mesozooplankton abundance and community composition during two cruises with RV ‘Polarstern’ in summer 2011 (warm AW) and 2012 (cold AW). Vertical multinet hauls covering five different depth strata were taken along a transect at 78° 50’ N. In both years, the zooplankton abundance was higher in the eastern (AW) as compared to the western Fram Strait (Polar water), with copepods dominating the communities. The basic community composition did not change significantly between years at distinct sampling stations, despite temperature differences of ~2°C in AW. Thus, trends for future community changes might only be observable in the long term.

Description: Automated detectors are important tools for processing large passive acoustic databases. Assessing the performance of a given method can be challenging and needs to be interpreted in the light of the overall purpose of analysis. Performance evaluation often involves comparison between thedetector output and a ground-truth data set, which often involves manual analyses of the data. Such analyses may be subjective depending on, e.g., interfering background noise conditions. In this study, we investigated the variability between two analysts in the detection of Antarctic blue whale Zcalls (Balaenoptera musculus intermedia), as well as the intra-analyst variability, in order to understand how this variability impacts the creation of a ground-truth and the assessment of detector performances. Analyses were conducted on two test datasets reflecting two basins and different situations of call abundance and background noise conditions. Using a ground-truth based on combined results of both analysts, we evaluated the performances of two automated detectors, one using spectrogram correlation and the other using a subspace-detection strategy. This evaluation allows understanding how recording sites, vocal activity, and interfering sounds affect the detector performances and highlights the advantages and limitations of each of the methods, and the possible solutions to overcome the main limitations.

Description: FRAM (FRontiers in Arctic Marine Monitoring) targets a modern vision of integrated underwater infrastructure. FRAM enhances sustainable knowledge for science, society and maritime economy as it enables truly year round observations from surface to depth in the remote and harsh arctic sea. Cutting edge technologies are being (further) developed and used to record essential ocean variables to improve our understanding of the Arctic and it’s ongoing processes. Data will be made freely available to the public via the AWI data portal.