Variations in the structural and functional diversity of zooplankton over vertical and horizontal environmental gradients en route to the Arctic Ocean through the Fram Strait

PLoS One. 2017 Feb 8;12(2):e0171715. doi: 10.1371/journal.pone.0171715. eCollection 2017.

Abstract

A multi-scale approach was used to evaluate which spatial gradient of environmental variability is the most important in structuring zooplankton diversity in the West Spitsbergen Current (WSC). The WSC is the main conveyor of warm and biologically rich Atlantic water to the Arctic Ocean through the Fram Strait. The data set included 85 stratified vertical zooplankton samples (obtained from depths up to 1000 metres) covering two latitudinal sections (76°30'N and 79°N) located across the multi-path WSC system. The results indicate that the most important environmental variables shaping the zooplankton structural and functional diversity and standing stock variability are those associated with depth, whereas variables acting in the horizontal dimension are of lesser importance. Multivariate analysis of the zooplankton assemblages, together with different univariate descriptors of zooplankton diversity, clearly illustrated the segregation of zooplankton taxa in the vertical plane. The epipelagic zone (upper 200 m) hosted plentiful, Oithona similis-dominated assemblages with a high proportion of filter-feeding zooplankton. Although total zooplankton abundance declined in the mesopelagic zone (200-1000 m), zooplankton assemblages in that zone were more diverse and more evenly distributed, with high contributions from both herbivorous and carnivorous taxa. The vertical distribution of integrated biomass (mg DW m-2) indicated that the total zooplankton biomass in the epipelagic and mesopelagic zones was comparable. Environmental gradients acting in the horizontal plane, such as the ones associated with different ice cover and timing of the spring bloom, were reflected in the latitudinal variability in protist community structure and probably caused differences in succession in the zooplankton community. High abundances of Calanus finmarchicus in the WSC core branch suggest the existence of mechanisms advantageous for higher productivity or/and responsible for physical concentration of zooplankton. Our results indicate that regional hydrography plays a primary role in shaping zooplankton variability in the WSC on the way to the Arctic Ocean, with additional effects caused by biological factors related to seasonality in pelagic ecosystem development, resulting in regional differences in food availability or biological production between the continental slope and the deep ocean regions.

MeSH terms

  • Animals
  • Arctic Regions
  • Biodiversity
  • Biomass
  • Ecosystem*
  • Environment*
  • Salinity
  • Temperature
  • Zooplankton*

Grants and funding

The research leading to the presented results has received main financing from the Polish Scientific Council project KongHau_ZOOM (2375/Svalbard/2012/2). Additionally, it was also a contribution of the Polish-Norwegian grant PAVE (Atlantic Water Pathways to the Arctic: Variability and Effects on Climate and Ecosystems, No. POL-NOR/202006/10/2013); the Research Council of Norway project CarbonBridge (Bridging productivity regimes in the Arctic Ocean, No. 226415/E10); the funds of the Leading National Research Centre (KNOW) received by the Centre for Polar Studies for the period 2014-2018, and, last but not least, from the budget of the statutory activity of the Institute of Oceanology, Polish Academy of Sciences (IO PAN). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.