Calanus finmarchicus basin scale life history traits and role in community carbon turnover during spring

Abstract

The copepod Calanus finmarchicus was investigated in four Subpolar Basins, Labrador, Irminger, Iceland, and Norwegian Seas, during spring, covering the time of ascent, grazing, and initiation of reproduction in the area. Lipid content, spawning activity, and stage composition and vital rates, such as egg and faecal pellet production were measured and linked to environmental parameters. Specific egg- and faecal pellet production rates varied with diatom biomass and were negatively correlated with temperature. Comparison of the various biological indicators revealed different life history traits C. finmarchicus has adopted in the different basins. In Labrador Sea, the females have invested in large eggs compared to the remaining basins. Labrador and Irminger Sea C. finmarchicus invest in size that we propose to be adaptation to cope with warmer overwintering habitats resulting in larger potential lipid storage capacity, while the Iceland and Norwegian Sea females can invest their remaining lipid storage in spring to fuel lipid-driven egg production. Grazing pressure on the phytoplankton community was estimated and compared between copepod and two dominating groups of protozooplankton; ciliates and heterotrophic dinoflagellates. Despite approximately the same biomass in the upper 100 m, the grazing impact of the protozoan grazers was an order of magnitude higher than the C. finmarchicus dominated mesozooplankton. This illustrates the importance to also include the smallest grazers when studying the spring bloom in high latitude marine ecosystems if the fate of the primary production should be fully understood.

Grazing, egg production and carbon budgets for Calanus finmarchicus across the Fram Strait

“…in good agreement with the published range for C. finmarchicus (Hirche et al, 1997;Mayor et al, 2006;Møller et al, 2016;Jońasdottir et al, 2022). The observed rates did not correlate with any measure of ingested food quantity or prey type.…”

“…This either suggests that the link between recent feeding history and egg production rate is weak, or that the rate at which eggs are produced is not directly limited by the available food. However, many studies have found a strong link between food quantity and egg production rate (Marshall and Orr, 1958;Hirche, 1990;Ohman and Runge, 1994;Hirche et al, 1997;Harris et al, 2000;Hirst and Bunker, 2003;Jońasdottir et al, 2022). Two of these studies were conducted in the Arctic, but the animals were either kept under identical feeding conditions for some time before experimentation (Hirche et al, 1997), or their eggs were only counted after 48 hours (Hirche, 1990), rather than 24 hours used herein, to allow for a longer spawning interval.…”

Primary Production and Respiration in the Norwegian Sea Estimated From Biogeochemical Argo Floats

“…Over this period a rise in Chl‐ a concentrations were noted, by approximately 0.25 mg m −3 (equivalent to 10.5 mg m −2 over a 42 m depth). By using a regional average C:Chl‐a ratio of 61 (Jónasdóttir et al., 2022; Roy et al., 2017) and a C:N ratio of 6.6 (Redfield et al., 1963) this increase in phytoplankton biomass was equivalent to a nitrate utilization of 0.2 μmol kg −1 . This marginal change in the nitrate time‐series was minor compared to the vertical nitrate flux.…”

Temporal patterns in multiple stressors shape the vulnerability of overwintering Arctic zooplankton

“…copepods play a pivotal role as they dominate the planktonic grazer biomass, are exceptionally adapted to polar regions and are sensitive to various stressors and chemical pollutants (Karnovsky et al., 2010 ; Kosobokova & Hirche, 2009 ; Sørensen et al., 2023 ). They serve as the link between primary production and higher trophic levels and contribute significantly to the carbon export and recycling of nutrients to the deep sea (Jónasdóttir et al., 2015 , 2022 ; Steinberg & Landry, 2017 ). The exposure to stressors can adversely affect their life cycle and could thus decrease the efficiency of the marine food web.…”