Abstract
Preliminary results of the pilot study of the zooplankton in the region between the Ross and Scotia Seas from November 2017 to April 2018 are presented. In total, 53 zooplankton samples were collected in the top 100 m water layer using vertical tows of a 0.1 m2 Juday net from four Ukrainian longliners operating during the Antarctic toothfish fishery. Total zooplankton abundance ranged from 3 to 2836 ind m−3 with a global mean of 360 ± 550 (±1 SD) ind m−3. The highest abundances were recorded at the northeastern Ross Sea. At those stations, small copepods (mainly Oithona spp., Oncaea spp., Ctenocalanus spp. and copepod nauplii) numerically dominated the samples. Total biomass ranged from 0.3 to 85 mg DW m−3 with a mean of 10.9 ± 14.5 mg DW m−3. The highest biomasses were recorded at the eastern Ross Sea, where pelagic tunicates Salpa thompsoni, siphonophores and ctenophora Callianira sp. accounted for >90% of total zooplankton biomass. At other stations, zooplankton biomass generally ranged from 5 to 20 mg DW m−3 with no clear pattern in distribution. The community composition was driven by the sampling latitude and/or season rather than longitudinally. This pilot study emphasized the unique opportunity to investigate zooplankton dynamics in the regions traditionally not sampled during the oceanographic surveys. It also created unprecedented opportunities to increase the seasonal and geographical zooplankton sampling coverage using ships of opportunity at a fraction of a dedicated oceanographic survey costs. The potential of such surveys are enormous in both providing invaluable information, contributing to existing long-term databases and enhancing an international collaboration in the Southern Ocean, particularly in light of recent modeling initiatives of the whole Antarctic system undertaken by the Commission for the Conservation of Antarctic Marine Living Resources.
Highlights
Zooplankton play a pivotal role in the world’s oceans, acting as a fundamental link between primary producers and top predators as well as commercially valuable fisheries [1,2,3]
In general, reflects the community composition and dynamic seasonal pattern of zooplankton in the region south of the Antarctic Convergence described in the literature [5,18,19,20,21]
Be pointed out that while average densities and biomass levels were within the documented range, it was on the higher side of the estimates
Summary
Zooplankton play a pivotal role in the world’s oceans, acting as a fundamental link between primary producers and top predators as well as commercially valuable fisheries [1,2,3]. Zooplankton contributes significantly to the biochemical cycling and export production affecting the cycling of carbon and other micro- and macronutrients in the ocean. It is a ubiquitous component of the biological pump mediating the organic matter removal from the surface to the deep ocean [4]. Zooplankton is extensively studied across marine environments, it is still poorly resolved in the biochemical and fisheries models. It is critical to gain a thorough understanding of the lower trophic level dynamics in pelagic ecosystems to be able to predict ecosystem responses under various climate change scenarios [6,7]
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