Copepod diapause and the biogeography of the marine lipidscape

Abstract

Aim One of the primary characteristics that determines the structure and function of marine food webs is the utilization and prominence of energy‐rich lipids. The biogeographical pattern of lipids throughout the ocean delineates the marine “lipidscape,” which supports lipid‐rich fish, mammal, and seabird communities. While the importance of lipids is well appreciated, there are no synoptic measurements or biogeographical estimates of the marine lipidscape. Productive lipid‐rich food webs in the pelagic ocean depend on the critical diapause stage of large pelagic copepods, which integrate lipid production from phytoplankton, concentrating it in space and time, and making it available to upper trophic levels as particularly energy‐rich wax esters. As an important first step towards mapping the marine lipidscape, we compared four different modelling approaches of copepodid diapause, each representing different underlying hypotheses, and evaluated them against global datasets. Location Global Ocean. Taxon Copepoda. Methods Through a series of global model runs and data comparisons, we demonstrated the potential for regional studies to be extended to estimate global biogeographical patterns of diapause. We compared four modelling approaches each designed from a different perspective: life history, physiology, trait‐based community ecology, and empirical relationships. We compared the resulting biogeographical patterns and evaluated the model results against global measurements of copepodid diapause. Results Models were able to resolve more than just the latitudinal pattern of diapause (i.e. increased diapause prevalence near the poles), but to also pick up a diversity of regions where diapause occurs, such as coastal upwelling zones and seasonal seas. The life history model provided the best match to global observations. The predicted global biogeographical patterns, combined with carbon flux estimates, suggested a lower bound of 0.031–0.25 Pg C yr−1 of downward flux associated with copepodid diapause. Main conclusions Results indicated a promising path forward for representing a detailed biogeography of the marine lipidscape and its associated carbon flux in global ecosystem and climate models. While complex models may offer advantages in terms of reproducing details of community structure, simpler theoretically based models appeared to best reproduce broad‐scale biogeographical patterns and showed the best correlation with observed biogeographical patterns.

Regional heterogeneity impacts gene expression in the subarctic zooplankter Neocalanus flemingeri in the northern Gulf of Alaska

“…N. flemingeri , a species that contributes to the high-latitude marine lipidscape 23 , depends on a short and variable annual phytoplankton bloom to: (1) mature and prepare for diapause; and (2) reach a location suitable for diapause (≥400 m depth) 24 . The persistence of N. flemingeri in the northern Gulf of Alaska and the subarctic Pacific indicates that enough individuals meet these two challenges in spite of high advection rates, patchy resource availability and interannual variability in the timing and magnitude of the spring bloom 18 .…”

“…The northern Gulf of Alaska is characterized by steep gradients in the physical and chemical environments driven by patterns in circulation, salinity, winds, and macro- and micro-nutrients 23 . Differences in the physical and chemical environment lead to resource gradients across the shelf, which impact the community composition and abundances of phytoplankton, microzooplankton, and mesozooplankton 18,19,24 .…”

Eat or Sleep: Availability of Winter Prey Explains Mid-Winter and Spring Activity in an Arctic Calanus Population

“…The timing of emergence and reproduction in spring affects the behaviors and success of Calanus in the following autumn (Varpe, 2012). It has generally been assumed that diapause is an essential stage in Calanus life history at mid to high latitudes (Hirche, 1996;Aksnes et al, 2004;Record et al, 2018) as a consequence of high seasonality in prey availability. However, scattered observations of active Calanus during the Polar Night have led to a range of expectations for overwinter Calanus behavior.…”

The Role of Zooplankton in Establishing Carbon Export Regimes in the Southern Ocean – A Comparison of Two Representative Case Studies in the Subantarctic Region

“…Zooplankton are part of the BCP, via ingestion of lower trophic levels, fecal pellet and carcass production and respiration of CO 2 (Schnack-Schiel and Isla, 2005;Turner, 2015;Steinberg and Landry, 2017). Furthermore, they actively transport carbon below the thermocline during daily migration and seasonal descent to overwinter at depth (Jónasdóttir et al, 2015;Klevjer et al, 2016;Steinberg and Landry, 2017;Record et al, 2018;Boyd et al, 2019). The role of zooplankton in the BCP is well-studied in some parts of the global ocean, e.g., the North Atlantic and the oxygen minimum zones in the Pacific (Jónasdóttir et al, 2015;Cavan et al, 2017), however, is less understood in the Southern Ocean.…”