Abstract: The Antarctic pelagic ecosystem over the continental shelf is dominated by the Antarctic silverfish Pleuragramma antarctica (Nototheniidae) which represents up to 90% of the fish biomass. P. antarctica is the only notothenioid species to have an entire pelagic life cycle. This species is characterized by a particularly long larval stage that lasts over a year and a vertical distribution with larvae in the surface layer and the older individuals in deeper ones. The reproductive cycle of P. antarctica is closely linked to seasonal sea ice dynamics and early stages depend on the spatial and temporal match with zooplankton production. P. antarctica is planktivorous at all stages of development, larvae are omnivorous actively feeding on diatoms and small copepods such as Oithona and Oncaea spp., while juveniles and adults are strictly carnivorous and feed mainly on copepods and euphausiids. In the early years of its life-history Antarctic silverfish exhibit primarily a marked transition in terms of trophic ecology between larvae and juveniles. The food resource partitioning is relatively clear between larvae and older life stages with a negligible overlap. Although the shift in diet between juveniles and adults remains less obvious in several geographic locations, juveniles and adults seem to share a similar mid-trophic level around Antarctica.

Abstract: NIPR Symposium

Zooplankton that live at high latitudes are influenced by seasonal cycles in primary productivity, the strength and position of major oceanographic
currents and the growth and decay of sea ice. Zooplankton are important prey for fish, especially in sheltered coastal regions that act as nurseries for larvae and juveniles.
To describe the influence of sea ice dynamics on the long term distribution of zooplankton and, in turn, their availability as prey for fish, sampling in the fast ice zone near Dumont d’Urville Station, located along the coast of Adélie Land in east Antarctica, has been carried out continually from 2000.
In the last fifteen years there have been five annual and ten summer field surveys that have sampled the underice zooplankton and ice-associated
fish, focussing on the stomach contents of the fish and abundance and diversity of the zooplankton. The fast ice of the region has been mapped via
satellites since 2001. Sampling of the sea ice itself began in 2003, with the ice meiofauna counted and identified from multiple ice cores.
The species of zooplankton recorded for the coastal region are typical of other Antarctic coastal areas and consist of small copepods such as Oithona
spp., Oncaea spp. and Stephos longipes, larger copepods including Metridia spp. and Calanoides acutus, meroplanktonic larvae, appendicularians and euphausiids. Meiofauna in the fast ice is dominated by copepods, particularly Drescheriella glacialis, Paralabidocera antarctica and Stephos longipes.
The abundance of zooplankton has varied at least 10-fold between years, producing consequences for the fish species that prey on them: in years of low zooplankton abundance the gut fullness of the fish is correspondingly low.

Abstract:

SOIS WG, SOOS. Hayama, Kanagawa 12-16 August 2017

Presentation of French activities in the Southern Ocean of interest for the Southern Ocean Observing System (SOOS) in the Indian part of the Southern Ocean.

Abstract: Abstract Multiple year?round records of bulk and size?segregated compositions of aerosol were obtained at the coastal Dumont d'Urville (DDU) and inland Concordia sites located in East Antarctica. They document the sea?salt aerosol load and composition including, for the first time in Antarctica, the bromide depletion of sea?salt aerosol relative to sodium with respect to seawater. In parallel, measurements of bromide trapped in mist chambers and denuder tubes were done to investigate the concentrations of gaseous inorganic bromine species. These data are compared to simulations done with an off?line chemistry transport model, coupled with a full tropospheric bromine chemistry scheme and a process?based sea?salt production module that includes both sea?ice?sourced and open?ocean?sourced aerosol emissions. Observed and simulated sea?salt concentrations sometime differ by up to a factor of 2 to 3, particularly at DDU possibly due to local wind pattern. In spite of these discrepancies, both at coastal and inland Antarctica, the dominance of sea?ice?related processes with respect to open ocean emissions for the sea?salt aerosol load in winter is confirmed. For summer, observations and simulations point out sea salt as the main source of gaseous inorganic bromine species. Investigations of bromide in snow pit samples do not support the importance of snowpack bromine emissions over the Antarctic Plateau. To evaluate the overall importance of the bromine chemistry over East Antarctica, BrO simulations were also discussed with respect data derived from GOME?2 satellite observations over Antarctica.