Importance of sympagic production to Bering Sea zooplankton as revealed from fatty acid-carbon stable isotope analyses

Abstract

We analyzed the fatty acid (FA) composition and carbon stable isotope ratios of individual FAs (δ 13 C FA ) of 3 zooplankton species (Themisto libellula, Calanus marshallae/glacialis, and Thysanoessa raschii) sampled from the Bering Sea during winter maximum ice extent, spring ice melt, and summer ice-free conditions in 2009 and 2010. Our goal was to assess diets of these ecologically important species and estimate the proportional contribution of pelagic and sympagic carbon sources to their diets. FA profiles showed little variation in diet within species between ice conditions or years but revealed differences in diet among species. FA biomarkers confirmed that T. libellula was predominately carnivorous and that C. marshallae/glacialis and T. raschii were primarily herbivorous. Estimates from 4 stable isotope mixing models using combinations of δ 13 C FA values of diatom FA markers (16:1n-7, 20:5n-3), and a flagellate FA marker (22:6n-3) showed that substantial, albeit highly variable, proportions of these FAs originated from organic matter originating from sea ice algae (T. libellula 36 to 72%, C. marshallae/glacialis 27 to 63%, and T. raschii 39 to 71%). Our results suggest that ice algae may be an important food source for zooplankton when water column phytoplankton are not available during critical periods in their life history. Predicted increases in water column phytoplankton production in the Bering Sea may help offset the expected reduction in ice algal production and any detrimental effects that this might have on consumers such as zooplankton. KEY WORDS: Sea ice algae • Phytoplankton • Compound-specific stable isotope analysis • Fatty acid biomarkers • Food web ecology • Climate change Resale or republication not permitted without written consent of the publisher 14:0

Chemical profiling of ancient hearths reveals recurrent salmon use in Ice Age Beringia

“…Spearman's correlation was used to examine the relationship between each food group and between hearths. We incorporated the δ 15 N, δ 13 C 16:0 , and δ 13 C 18:0 values of the hearths and food groups as well as burning enrichment factors (δ 13 C ±0.1‰ and δ 15 N ±0.3‰) (49) and concentration dependencies (50) in a SIAR mixing model to estimate the proportional contribution of the three food groups (marine, freshwater, and terrestrial) to each hearth (SI Materials and Methods).…”

Characterizing Spatial Variability of Ice Algal Chlorophyll a and Net Primary Production between Sea Ice Habitats Using Horizontal Profiling Platforms

“…However, net sympagic (ice-associated) primary production is relatively low accounting for 1-10% of total NPP in the Arctic Ocean (Dupont, 2012;Arrigo and van Dijken, 2015). Regardless of the overall low contribution of sympagic NPP, both sympagic and pelagic organisms showed a high dependency on ice-algae produced carbon within the central Arctic Ocean (Budge et al, 2008;Wang et al, 2015;Kohlbach et al, 2016Kohlbach et al, , 2017. The key role of sea ice algae in Arctic foodwebs, particularly in terms of reproduction and growth of key Arctic organisms, such as: Calanus glacialis (Michel et al, 1996;Søreide et al, 2010), highlights the importance of timing and duration of ice algal growth, and the availability of algal biomass throughout different times of the year.…”

Ice Algae-Produced Carbon Is Critical for Overwintering of Antarctic Krill Euphausia superba

“…The mixing models can account for different isotopic turnover rates in the consumers. However, krillspecific trophic enrichment of 13 C is unknown, and was thus assumed to be zero for both BSIA and CSIA models (Budge et al, 2011;Graham et al, 2014;Wang et al, 2015). For the BSIA models, trophic enrichment of 15 N was assumed to be 3.4‰ per trophic level (Minagawa and Wada, 1984).…”

“…In contrast, δ 13 C values of trophic marker FAs are assumed to be unchanged by metabolic processes, and independent from the chemical composition of organisms. CSIA allows estimating δ 13 C in individual marker FAs to accurately trace and quantify sea ice-produced carbon in food webs (Wang et al, 2015;Kohlbach et al, 2016). Here, we applied for the first time both stable isotope methods to quantify the relative dependency of overwintering krill on ice algae-produced carbon.…”

“…The isotopic composition of biomolecules from ice algae is transferred through the food web by organisms ingesting ice algae-produced carbon either directly or indirectly by carnivorous or detritivorous feeding. The isotopic fractionation of carbon (δ 13 C: 13 C/ 12 C) has therefore been used in polar organisms to estimate their relative dependency on ice algaeproduced carbon (Budge et al, 2008;Wang et al, 2015;Jia et al, 2016;Kohlbach et al, 2016Kohlbach et al, , 2017. In this study, we estimated the relative dependency of krill on carbon produced by ice algae in terms of the proportional contribution of ice algae-produced carbon to the body carbon of krill (α Ice ), based on bulk stable isotope analysis (BSIA) and compound-specific stable isotope analysis (CSIA) of marker FAs.…”