Trophic structure and biomass of high-Arctic zooplankton in the Eurasian Basin in 2017

Hauke.Flores [ at ]


The Arctic Ocean is experiencing some of the most pronounced effects of global climate change. Sea ice coverage and thickness have significantly decreased in the past decades and are predicted to continue in the future. Significant changes in the water column are expected to occur in the environment, such as increases of surface water temperature, ocean acidification, increased stratification, changes in circulation of water. With ongoing climate change, model-based studies indicate a northward migration of Atlantic species with an increased inflow of Atlantic water into the Arctic Ocean. A biogeographical shift in the increasing dominance of warm-temperate-boreal copepod species has been witnessed over the last decade in the Arctic Ocean. The northward expansion of zooplankton communities associated with warm Atlantic waters (AW) leads to a reduction in the number of cold water species. Changes in the zooplankton community will also lead to the changes in its quality as a food source for higher organisms in the Arctic food chain, since zooplankton is one of the main link in the Arctic food web. In this study pelagic zooplankton collected during the Polarstern expedition PS106 from 28 May to 20 July 2017 in the Arctic Ocean, north of Spitsbergen and the Barents sea, were analyzed. The research area comprised stations located on the shelf and slope of the Barents Sea and in the western Nansen Basin. In the sampling area Atlantic inflow from the Fram Strait meets the outflow of the Barents Sea and the southward-moving sea ice and polar surface waters. The Barents Sea shelf slope is a hot spot of atlantification and borealisation. The zooplankton community in this area is highly influenced by all these factors. Therefore, the objectives of this study were to investigate the variability in macrozooplankton species composition, biomass, and size composition of macro- and mesozooplankton across the Barents Sea shelf slope in relation to spatial and water masses influence parameters. In addition, the trophic structure of zooplankton communities was investigated, analyzing the stable isotopic composition and C:N ratio of zooplankton. The AW masses were distributed almost at all stations. To assess the influence of water masses, the stations were divided into two groups: with a smaller and greater influence of AW. 6 According to the obtained data, the total biomass of zooplankton was highest on the shelf. On the slope, zooplankton biomass was significanly lower than in the Nansen Basin. The smaller size fractions predominated at the stations more exposed to AW. Conversely, the contribution of large fractions in the Nansen Basin was significantly greater. The taxonomic composition of macrozooplankton in the upper 100 m comprised at least 21 taxa. The results indicated a significantly higher number of taxa on the shelf and slope (19 taxa) than in deep-sea areas (15 taxa). The results of the stable isotope analysis indicated that carbon sources and trophic structure of zooplankton on the shelf slope differed significantly from the zooplankton community in deep-water stations with reduced AW influence. Also, the C:N ratio on the slope was significantly lower than in the Nansen Basin, indicating a lower lipid content in shelf-associated zooplankton. The results obtained for the isotopic composition of the four macrozooplanton species Themisto libellula, Themisto abyssorum, Thysanoessa longicaudata, Thysanoessa inermis did not show statistically significant inter-specific differences in trophic level, carbon source and C:N ratio. In general, the results of the study confirm the changes taking place in the zooplankton community and the impact of the region's atlantification. The unexpected result was that the zooplankton biomass on the slope was no higher than in the deep basin. This is contrary to the general assumption that the zooplankton biomass is higher on the AW-affected slope and will increase in the future. Some of the data require more comprehensive analysis including additional environmental and biological datasets, when they will become available.

Item Type
Thesis (Master)
Primary Division
Primary Topic
Publication Status
Eprint ID
Cite as
Zakharova, N. (2019): Trophic structure and biomass of high-Arctic zooplankton in the Eurasian Basin in 2017 , Master thesis, Saint Petersburg University / University of Hamburg POMOR.

[thumbnail of Zakharova_MT.pdf]

Download (2MB) | Preview

Add to AnyAdd to TwitterAdd to FacebookAdd to LinkedinAdd to PinterestAdd to Email

Geographical region

Research Platforms

PS > 106

Edit Item Edit Item