Trophic Dynamics of Calanus hyperboreus in the Pacific Arctic Ocean

Abstract

The Pacific Arctic Ocean receives relatively warm and nutrient-rich Pacific summer water inflow via the Bering Strait and the Chukchi Sea. The East Siberian Sea, which is productive and shallow, is situated in the western part of the Pacific Arctic Ocean (Semiletov et al., 2005). In the eastern region, the northern Chukchi Sea, which is poor surface nutrient and have deep basin, is partially located at the surrounding area of the anticyclonic Beaufort Gyre (Coupel et al., 2015). The Pacific Arctic Ocean exhibits rapid responses to environmental change. Strong stratification is caused by incoming sea ice meltwater in summer (McLaughlin et al., 2011). The nutricline and surface chlorophyll maximum (SCM) depth can be deepened by stratification, decreasing primary productivity due to limited nutrient supplies (Coupel et al., 2015; Zhuang et al., 2018). The zooplankton community is tightly tied to the hydrodynamic condition and depends on the composition of their diets. In low-nutrient conditions and a stable water column, smaller phytoplankton such as pico-and nanoplankton are usually dominant (Coupel et al., 2012; He et al., 2012; Li et al., 2009). Whereas, diatom was dominant under high sea ice concentration in nutrient-rich and vertically mixed water column (Lee et al., 2019). The composition of primary producers, the cell sizes of which vary widely,

Ecological Traits of Fish for Mercury Biomonitoring: Insights from Compound-Specific Nitrogen and Stable Mercury Isotopes

“…In regards to the site-specific difference, both LB and PG at the YS River exhibit significantly ( t -test, two-tailed; p = 0.001) lower δ 15 N Phe (5.3 ± 2.8‰, n = 4) compared to other study locations (10.3 ± 2.3‰, n = 19), reflecting a higher atmospheric N source contribution relative to terrestrial sources. The δ 15 N Phe of the YS River are consistent with copepod collected from the Arctic Ocean (1.9 to 6.0‰, n = 22), which dominantly consume phytoplankton that assimilate atmospheric N . LB and PG at the remaining riverine systems (HN, GM, ND) are characterized by elevated δ 15 N Phe , which are higher compared to various biota compiled from coastal marine (3.5–8.7‰) and stream ecosystems (−4.8 to 6.3‰) (Figure ).…”

“…In other words, when the effect of trophic-induced fractionation (δ 15 N Glu ) is removed from TP corrected (eq ) and only the source amino acid (δ 15 N Phe ) is taken into account, we observe a significant negative correlation with Δ 199 Hg, reflecting different Hg sources. For instance, in the YS River, LB exhibited the lowest δ 15 N Phe , reflecting atmospheric N, , and the highest Δ 199 Hg values, similar to fish influenced by wet Hg deposition (Figure ). , This is also supported by the slightly more elevated Δ 200 Hg observed in LB at the YS River relative to other riverine systems.…”

Distribution of siphonophores in the Northwest Pacific Ocean and links to environmental conditions

“…For the analysis of the nitrogen isotopes of individual AAs (d 15 N AA ), we used two to three individuals of the non-gelatinous zooplankton (copepods, euphausiids, and amphipods) and one individual of the gelatinous zooplankton. The experimental protocol has been described in a previous study (Choi et al, 2021). AA nitrogen isotopes were analyzed using a gas chromatograph (HP 6890N, Agilent, USA) connected to a combustor (GC5 Interface, Elementar, Germany) and an isotope ratio mass spectrometer (Isoprime 100, Elementar, Germany).…”

“…Meanwhile, d 15 N analysis of individual amino acids (AAs) has been increasingly used to understand the TP of consumers based on the separation between trophic enrichment and basal nitrogen sources (trophic and source AAs, respectively) (Chikaraishi et al, 2009;McMahon and McCarthy, 2016;Choi et al, 2017). The TPs of zooplankton provide informative signals of dietary composition and variation based on environmental changes (Dećima et al, 2013;Loick-Wilde et al, 2019;Choi et al, 2021). The d 15 N of AAs could provide a better understanding of trophic ecology, including both gelatinous and non-gelatinous zooplankton.…”

Spatial and Interannual Patterns of Epipelagic Summer Mesozooplankton Community Structures in the Western Arctic Ocean in 2016–2020

“…Although zooplankton are abundant and ecologically important in Arctic food webs, their trophic dynamics and ecological roles remain unclear (Choi et al., 2021; Iken et al., 2010) due to the scarcity of comprehensive oceanographic and biological research. Zooplankton communities at the Arctic Ocean boundary are more susceptible to environmental changes in polar oceans because they are strongly influenced by hydrographic factors, such as the formation or melting of sea ice, surface cooling, and convection (Matsuno, Sanchez et al., 2016; Spear et al., 2019).…”