Natural dimethyl sulfide gradients would lead marine predators to higher prey biomass

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Owen, K., Saeki, K., Warren, J. D., Bocconcelli, A., Wiley, D. N., Ohira, S., Bombosch, A., Toda, K., & Zitterbart, D. P. Natural dimethyl sulfide gradients would lead marine predators to higher prey biomass. Communications Biology, 4(1), (2021): 149, https://doi.org/10.1038/s42003-021-01668-3.Finding prey is essential to survival, with marine predators hypothesised to track chemicals such as dimethyl sulfide (DMS) while foraging. Many predators are attracted to artificially released DMS, and laboratory experiments have shown that zooplankton grazing on phytoplankton accelerates DMS release. However, whether natural DMS concentrations are useful for predators and correlated to areas of high prey biomass remains a fundamental knowledge gap. Here, we used concurrent hydroacoustic surveys and in situ DMS measurements to present evidence that zooplankton biomass is spatially correlated to natural DMS concentration in air and seawater. Using agent simulations, we also show that following gradients of DMS would lead zooplankton predators to areas of higher prey biomass than swimming randomly. Further understanding of the conditions and scales over which these gradients occur, and how they are used by predators, is essential to predicting the impact of future changes in the ocean on predator foraging success.Open Access funding enabled and organized by Projekt DEAL. This study was funded by the Herrington Fitch Family Foundation, by the Woods Hole Oceanographic Institution Joint Initiative Awards Fund from the Andrew W. Mellon Foundation and The President’s Investment Fund, and by KAKENHI, Grants-in-Aid for Basic Research (B) (Grant no. 16H04168) and Bilateral Programs Joint Research Projects (open partnership), both from the Japan Society for the Promotion of Science. The authors thank Mrs. Norio Hayashi, Takanori Nagahata, and Ms. Mihoko Asano (Mitsubishi Chemical Analytech Co.) for their support with the SGV-CL device. The research was conducted under Scientific Research Permit number 18059, issued by the National Oceanic and Atmospheric Administration under the Marine Mammal Protection Act

FjordPhyto: la experiencia de un proyecto de ciencia ciudadana en la Antártida que involucra turistas y microalgas

Desde hace más de 5 años las y los viajeros que visitan el continente antártico durante los meses de verano (noviembre - marzo) ayudan a las y los investigadores a monitorear cambios en la comunidad fitoplanctónica en relación al derretimiento glaciar. La Península Antártica es una región que está experimentando cambios rápidos debidos al calentamiento global. El fitoplancton (microalgas) es la base de la red alimenticia marina y es ignorado por la sociedad debido a su tamaño microscópico. A su vez, el turismo antártico es una industria actualmente en aumento y diversificación. Los proyectos de ciencia ciudadana son una excelente herramienta para educar al turismo en cuanto a conservación e impactos del cambio climático. El proyecto FjordPhyto nace como una colaboración entre investigadores (principalmente de Estados Unidos y Argentina) con la Asociación Internacional de Operadores de Tours Antárticos (IAATO por sus siglas en inglés). Este proyecto de ciencia ciudadana aprovecha las embarcaciones turísticas como plataformas para tomar muestras e involucrar a la comunidad viajera en el legado de la investigación polar. El proyecto FjordPhyto busca crear concientización en las y los turistas sobre estas comunidades microscópicas, que incluso tienen la oportunidad de observar con un microscopio a bordo.Facultad de Informátic

Marine Biology in Antarctica: Then and Now.

Marine life around Antarctica, dictated by its extreme climate, has always been a fascinating topic for biologists. In the 19th century, first documentations of the abundant marine life were revealed through the eyes of the first sealers. Those expeditions further contributed significant information on the diversity and distribution of Antarctic marine life (McClintock, Amsler et al. 2001). But despite several expeditions, Antarctica was regarded as a 'terra incognita' at the end of the 19th century. The beginning of the 20th century, however, brought a change with the departure of several scientific expeditions into Antarctic regions. While geographical exploration and magnetic studies were of major importance, biologists were eager to discover and study the marine life and its adaptations to the Antarctic climate (McClintock, Amsler et al. 2001; Lüdecke 2003). Until today, Antarctic marine biology has undergone major changes, but is still of major interests for marine biologists, due to its extreme environments and importance in the world's ocean cycles (Hempel 2007). Six expeditions (Table 1), leaving into Antarctic regions at the turn of the 19th century, were selected for this report and will be investigated for methods and research areas of marine biology. These methods will further be compared to and reviewed for their influence on modern studies in marine biology. A further aspect includes international collaboration of scientific studies during early expeditions and today

Euphausia Superba or Salpa Thompsoni – Who is going to win?

Antarctic krill Euphausia superba and the salp Salpa thompsoni are major grazers in the Antarctic ecosystem, in which krill plays a major role in the link between primary producers and higher trophic levels. Both species are widely distributed in the Southern Ocean, but they exhibit a spatial segregation. Krill is predominantly found in colder waters of the high latitudes, whereas salps occupy warmer water masses in the lower latitudes. Over the last decades a shift in salp distribution into regions further south has been observed. Simultaneously krill abundance in those areas has decreased. This might indicate that a large-scale environmental shift in Antarctic regions may have occurred, or is in progress which will have major impacts on the cycling of biogenic carbon the Southern Ocean as well as on krilldependent species

Soundscapes of the Southern Ocean: Passive Acoustic Monitoring in the Weddell Sea

The Southern Ocean provides an important habitat for marine mammals, both residential and migratory, yet long term studies of their habitat usage are hampered by the region’s seasonal inaccessibility. To overcome this problem, two autonomous underwater passive acoustic recorders were deployed in the Weddell Sea in 2008 to collect multiyear passive acoustic data. The recorders were retrieved in 2010 and the acoustic recordings were analyzed in terms of broad- and narrow-band noise. Noise in this context is defined as the acoustic energy not assignable to a specific singular source. It comprises both biotic as well as abiotic components. Noise levels were determined by selecting the quietest 10 s of each 5 min recording to exclude energetic contributions from nearby singular acoustic sources. The respective sound pressure levels (SPL) and spectra were correlated with time series of environmental covariates. The ambient noise levels of both recorders were found to be highly variable in time, ranging from 102 to 115 dB re 1 μPa (broadband SPL 5th and 95th percentile), and were correlated with the sea ice cover and wind speed. The annual variation of the ice cover caused a bimodal distribution of broadband SPL. In winter the SPL mode was 106 dB re 1 μPa. By contrast, storms over the open ocean in summer resulted in an SPL mode of 111 dB dB re 1 μPa. Variation in the ambient noise spectra could be correlated to wind speed and ice coverage. The acoustic presence of several mysticete (Antarctic blue whale, Balaenoptera musculus intermedia, fin whale, Balaenoptera physalus) and pinniped (leopard seal, Hydrurga leptonyx, crabeater seal, Lobodon carcinophaga) species created distinct bands in the spectra that contributed considerably to ambient noise levels. Comparison of the timing of these noise bands between the two acoustic data sets revealed offsets in the occurrence of acoustic activity between both recorders, suggestive of marine mammal latitudinal migration. At 66°S (the northern recorder position) fin whales were acoustically present earlier and longer in summer than at 69°S. Similarly, the blue whale chorus was more intense at 66°S than at 69°S. This might be related to the response of these species to the seasonal variation in the extension and density of sea ice. Seasonal cycles were also detected in the noise band attributed to crabeater seal vocalisations. They were annually present in September and November, followed by the leopard seals noise band, which is discernible between December and January. Results from this latitudinal recorder pair give a first impression on possible marine mammal migration patterns as well as the spatial and temporal distribution of marine mammal acoustic presence in the Southern Ocean. Additional recorders deployed in the basin wide HAFOS array will expand the spatial and temporal resolution of the acoustic dataset and allow conducting detailed multiyear studies of marine mammal acoustic presence and behavior throughout the Weddell Sea

Modeling year-round marine mammal habitat preferences in the Southern Ocean based on passive acoustic observations

An understanding of marine mammal distribution patterns forms the basis of the design and implementation of effective management measures. Habitat modeling offers a valuable approach to combine information on species presence (or absence) with local environmental parameters to explore species-specific habitat affinities. Most habitat modeling approaches require marine mammal presence-absence data which can only be obtained during dedicated visual surveys. However, in the Southern Ocean, the collection of visual data is complicated by the region’s remoteness, limited seasonal accessibility and the dependency on favorable light and weather conditions to conduct visual observations. Passive acoustic monitoring, by contrast, is highly suitable for long-term monitoring of marine mammals as they use sound in many behavioural contexts and species can be readily identified by their acoustic signatures. Passive acoustic data provide accurate information on temporal patterns in acoustic presence and time spent in the vicinity of the recorders. Furthermore, knowledge on the behavioral context in which specific sound types are produced can be used to derive information on habitat usage. Here we describe an approach for combining multi-year, year-round marine mammal presence data from passive acoustic recorders with a selected set of relevant environmental parameters to develop species-specific habitat models. Our project comprises multi-year passive acoustic data collected in Antarctic coastal as well as offshore areas throughout the Weddell Sea. Some of the species recorded are sighted only rarely during visual surveys, but are acoustically abundant in our recordings, such as the Antarctic blue whale (Balaenoptera musculus intermedia), humpback whale (Megaptera novaeangliae), fin whale (B. physalus), leopard seal (Hydrurga leptonyx), crabeater seal (Lobodon carcinophaga) and Ross seal (Ommatophoca rossii). The model will incorporate both static environmental variables, such as depth or slope, and dynamic variables, such as sea surface temperature, sea surface height, sea ice concentration and their derivatives. The project aims at furthering our current understanding of marine mammal habitat affinities in the Southern Ocean by constructing species-specific habitat models at yet unprecedented spatial and temporal time scales

Challenges of the Southern Ocean - "The Antarctic Beyond the Continent".

The Southern Ocean is the fourth largest ocean in the world, it sustains a wide variety of marine life and plays a significant role in the global climate. No legal definition of the Southern Ocean exists, although there are biological and physical boundaries. Various human activities, such as science, tourism, bioprospecting and fishing have been identified. They pose environmental and legislative challenges to the Southern Ocean which have not yet been fully resolved. Climate change, which is often neglected as a result of human activity, is also interfering with the marine ecosystem. The current shortcomings in regulating these activities have been identified and recommendations have been made in order to protect the future of the Southern Ocean. The Southern Ocean is the fourth largest ocean in the world, it sustains a wide variety of marine life and plays a significant role in the global climate. No legal definition of the Southern Ocean exists, although there are biological and physical boundaries. Various human activities, such as science, tourism, bioprospecting and fishing have been identified. They pose environmental and legislative challenges to the Southern Ocean which have not yet been fully resolved. Climate change, which is often neglected as a result of human activity, is also interfering with the marine ecosystem. The current shortcomings in regulating these activities have been identified and recommendations have been made in order to protect the future of the Southern Ocean

Passive Acoustic Monitoring of ambient noise in the Atlantic sector of the Southern Ocean

With increasing marine traffic, the global level of anthropogenic noise is likely to rise. This might induce further stress to already endangered marine mammals, which rely on their acoustic senses for foraging, orientation and communication. The Southern Ocean provides an important habitat for marine mammals, both residential and migratory. To study its cetacean and pinniped populations as well as the ambient soundscape, autonomous underwater recorders were deployed on moorings in the Atlantic section of the Southern Ocean. Natural ambient noise is generated by the interaction of wind, waves, ice, biological and geological sources and subject to seasonal variations. Transient sounds such as whale and seal vocalisations strongly influence the acoustic spectra. Due to limited marine traffic and industrial activity the Southern Ocean contrasts regions with anthropogenic noise pollution on the northern hemisphere. This rather uninfluenced soundscape is analysed according to indicators as proposed under the European Union marine strategy frameworks directive. In this way a useful reference to the northern hemisphere oceans is given. The scope of anthropogenic and natural noise as well as sound examples will be presented