Krill distribution in relation to environmental parameters in mesoscale structures in the Ross Sea

Abstract Krill, a key pelagic resource of the Antarctic food web, provides an important link between primary and secondary plankton production and top predators. Since krill abundance is a crucial factor in Antarctic ecosystem functioning, its monitoring supplies vital data. Acoustic surveys are an effective approach to estimating krill abundance. An acoustic survey was conducted in the western Ross Sea in January 2014–10 years after a similar survey by our team - to estimate krill abundance and biomass and monitor oceanographic conditions. Antarctic krill ( Euphausia superba ) was detected in the northern part of the western Ross Sea and dense swarms of ice krill ( Euphausia crystallorophias ) were found in its central coastal area. Data analysis revealed an inverse correlation between E. superba density and salinity in the water column, whereas a positive correlation was found between E. crystallorophias abundance and fluorescence; the latter relationship was confirmed in thematic maps of E. crystallorophias spatial distribution and fluorescence. Comparison of 2004 and 2014 biomass data showed a much greater abundance of both species in the more recent survey.