The global contribution of seasonally migrating copepods to the biological carbon pump

Abstract

Every year, large numbers of zooplankton migrate from the surface ocean to depths of 500–2000 m to hibernate. Through this migration, they actively transport organic carbon to the deep ocean, where it is used to fuel metabolic needs. This active transport of carbon is thought to be highly efficient, as carbon metabolized by copepods is directly injected deep into the ocean's interior. The significance of this process in view of global carbon cycling remains an open question. Here, we focus on five representative, diapausing copepod species (Calanus finmarchicus, Calanus hyperboreus, Calanoides acutus, Calanoides natalis, and Neocalanus tonsus) distributed in the Arctic, Atlantic, Indian, and Southern Oceans. For each species, we compute both carbon injection (how much carbon is transported below the euphotic zone during zooplankton migration and left there as dissolved inorganic carbon) and carbon sequestration (the amount of carbon stored in the ocean's interior following diapausing zooplankton‐mediated injection). In total, the five species considered here contribute 0.4–0.8% of total biological carbon export, and 0.8–3.3% of total carbon sequestration mediated by the biological pump (assuming a total carbon export of ~ 10 PgC yr−1 and sequestration of ~ 1300 PgC). Including other species in this inventory would increase the contribution of diapausing copepods to the biological carbon pump, but requires more precise estimates of copepods' distribution, abundance, and metabolic requirements.

Starvation reduces thermal limits of the widespread copepod Acartia tonsa

“…Primarily herbivorous copepods may, therefore, be particularly vulnerable to warming compared to omnivorous species like A. tonsa , which may avoid starvation and the accompanying reduction in thermal limits by feeding on heterotrophic microzooplankton. Given the large contributions of herbivorous species to carbon flux in marine systems (Pinti et al, 2023 ), these shifts in community composition driven by differential environmental sensitivity would have important biogeochemical consequences.…”

“…Copepods are the some of the most abundant animals on the planet, and dominate planktonic communities in the coastal ocean (Turner, 2004 ). By nature of their abundance, this group plays key ecological and biogeochemical roles in aquatic systems (Brun et al, 2019 ; Pinti et al, 2023 ; Steinberg & Landry, 2017 ). In particular, copepods are important consumers of primary productivity, and act as a crucial linkage between phytoplankton and higher trophic levels (Castonguay et al, 2008 ).…”

Industrial fisheries have reversed the carbon sequestration by tuna carcasses into emissions

“…However, it would also be necessary to study whether the deficit of predation due to the extraction of predators is not inducing an increase in the biomass of prey, in particular the mesopelagic micronekton (Pinti et al, 2023), which would then compensate a part of the loss in carbon sequestration due to top predator exploitation.…”

“…So, tunas and other marine vertebrates certainly represent an underestimated carbon sink toward climate change mitigation and an additional option in the portfolio of NCS. However, it would also be necessary to study whether the deficit of predation due to the extraction of predators is not inducing an increase in the biomass of prey, in particular the mesopelagic micronekton (Pinti et al, 2023), which would then compensate a part of the loss in carbon sequestration due to top predator exploitation.…”

Pathogens and Passengers: Roles for Crustacean Zooplankton Viruses in the Global Ocean

“…Up to 50% of zooplankton above 500 m perform diel vertical migration (DVM), rising to the surface to feed at night [161]. The diel and seasonal vertical movements of zooplankton transfer organic material between layers with high energetic barriers to mixing, connecting epi-and mesopelagic plankton communities and sequestering carbon [162][163][164]. Zooplankton are infected by and carry viruses, and infected individuals could release virus particles when they are migrating, consumed or dying.…”