Edwards, B. R. | bioRxiv Science

bioRxiv2026

Biochemical Indicators of Atlantification and Diapause Strategy in Arctic Copepods Point to a Decrease in Copepod-mediated Carbon Sequestration

Arctic ecosystems are critically endangered by rising temperatures and changing hydrography, especially the intrusion of increasingly warm water from the Atlantic Ocean known as Atlantification. In addition to housing fragile biodiversity, Arctic copepods and their lipids play a crucial role in cycling carbon by transporting carbon into the deep ocean through their diapausing behaviors. Here, we explored the lipidomes of the Arctic copepod Calanus glacialis, collected from three fjords around Svalbard during November 2022 when C. glacialis are known to be in diapause. These three field sites provide a natural laboratory experiment, as they are influenced by different water masses with varying degrees of Atlantic water, and experience vast differences in sea ice coverage over the year. These environmental differences were clearly reflected in the lipidomic analysis, with stations influenced most by Atlantic Warm Water having the lowest total lipid concentrations and the lowest accumulation of storage lipids necessary for entering diapause. Membrane lipids were a significant proportion of the Svalbard copepod lipidomes, with the highest ratios observed at the Atlantified site. The high membrane lipid and high triacylglycerol concentrations were interpreted as signs of active feeding. This was further corroborated by fatty acid composition analysis, which revealed dietary biomarkers of carnivory at Atlantified sites. The copepods from the site most insulated from Atlantic influence had more than double the amount of storage lipids per individual and fatty acids associated with diatom biomass, indicating assimilation in the spring. Ultimately, the decrease in lipid content observed in association with Atlantification around Svalbard will impact diapause patterns, as Calanus species need 20-30% more WE to successfully complete diapause. In turn, this will impact the magnitude of carbon sequestration through the seasonal lipid pump, not to mention having radiating effects through the Arctic food web where Calanus glacialis plays an important role. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=131 SRC="FIGDIR/small/738257v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@131e2org.highwire.dtl.DTLVardef@72071aorg.highwire.dtl.DTLVardef@3059f0org.highwire.dtl.DTLVardef@60a5ea_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗

bioRxiv2025

Viral infection induces oxylipin chemical signaling at the end of a summer upwelling bloom: implications for carbon cycling.

Abstract/SummaryDiatoms are large phytoplankton that form the base of the marine food web and often bloom first when nutrients are injected into the surface ocean through upwelling or deep ocean mixing1,2. Diatoms contribute 20% of global photosynthesis3 while disproportionately representing 40% of carbon export4, with most export occurring along the continental margins5. Oxylipin chemical signaling by diatoms has been extensively studied in the Mediterranean Sea where oxylipins are linked to grazing with subsequent insidious effects on copepod reproduction6-13. Culture studies with diatoms have shown that stress, growth phase, and viral infection also impact oxylipin production14-16. This study provides insight into the role of oxylipins as biomarkers and chemical signals during viral infection of diatoms in natural communities. Biomarkers for lysis and senescence were identified in laboratory experiments and observed at elevated concentrations in meta-lipidomes collected in the California Coastal Ecosystem (CCE) where diatoms had recently been lysed by viruses17. Deck-board incubations with natural communities show that oxylipins stimulate sinking particle-attached and surface-ocean microbes in a dose and community-dependent manner, while inhibiting microzooplankton grazing and phytoplankton growth rates. Carbon export was two times higher at the Post-lytic site than elsewhere along the transect consistent with the viral shuttle, whereby viruses facilitate carbon export. We previously reported enhanced enzymatic activity at the Post-lytic site17, suggestive of the viral shunt, whereby carbon is remineralized or attenuated into non-sinking dissolved organic matter. Here we layer geochemical evidence to show that lysis of oxylipin producing diatoms amplified the vertical flux of carbon from the surface ocean even in the presence of viral shunt processes. The remineralization length scale and community composition have been hypothesized as controls on shunt vs. shuttle18-20; our analysis provides another example of how community interactions may toggle a system between favoring shunt or shuttle.

ecology↗