The impact of seasonal regulation of metabolism on the life history of Antarctic krill

Abstract

Antarctic krill up-and down-regulate their metabolism as a strategy to cope with the strong seasonal environmental fluctuations in the Southern Ocean. In this study, we investigate the impact of this light-and temperature dependent metabolic regulation on growth, reproduction and winter survival of krill. Therefore, we advance a bioenergetic growth model of krill by adding a data-derived scaling function of krill activity. With SERBIK (SEasonally Regulated BIoenergetic Krill growth model), we conduct a numerical experiment which tests the impact of such scaling on krill life history under two different winter food conditions: In the first scenario, we simulate life history of krill when winter food availability is low; in the second scenario, winter food availability is increased within realistic ranges. The results demonstrate that the scaling of metabolism is especially important during low food winters. Reducing metabolism during winter permits individuals to grow to larger body length, reproduce successfully and release a greater number of eggs. It further significantly reduces withinyear size fluctuations caused by starvation during months with low food availability. Finally, SERBIK can be used in future spatial modelling studies which include movement of krill along latitudinal gradients and thus spatiotemporal gradients in light-and temperature.

Classic or hybrid? The performance of next generation ecological models to study the response of Southern Ocean species to changing environmental conditions

“…Seasonality is a fundamental feature of environmental systems. It is particularly critical to life in temperate and high latitudes, and one key phenomenon to consider for studying both species distribution (Morelle & Lejeune, 2015; Zuckerberg et al, 2016) and metabolism (Bahlburg et al, 2021).…”

The Impact of Salps on the Antarctic Krill Population - An Individual-based Modelling Study

“…In this study, and for the first time, we linked an individual-based energy budget model of krill (Euphausia superba) (Bahlburg et al, 2021;Jager & Ravagnan, 2015) with an individual-based model simulating the life history of salps (Salpa thompsoni) (Groeneveld et al, 2020). We investigated the effect of food competition between krill and salps as well as the influence of varying food densities on the population dynamics of krill over a period of 100 years.…”

“…The individual-based model PEKRIS was implemented in NetLogo (Wilensky & Rand, 2015) version 6.2 and builds on existing salp population dynamics models (Groeneveld et al, 2020;Henschke et al, 2018). We extended this model by implementing krill individuals following a simplified dynamic energy budget theory (Bahlburg et al, 2021;Jager et al, 2013;Sousa et al, 2010). The PEKRIS model description follows the Overview, Design and Details protocol suggested by (Grimm et al, 2006(Grimm et al, , 2020 and is presented in the following sections.…”

“…Patterns used for validating the model results against empirical and simulated data are trajectories for maximum sizes, metabolic activities or reproductive outputs and ranged therefore from the individual krill or salp to the population level known from literature (Atkinson et al, 2006;Dubischar et al, 2006;Iguchi & Ikeda, 2004;Ikeda, 1981;Ikeda & Mitchell, 1982;Nicol et al, 1995;E. A. Pakhomov & Hunt, 2017;Siegel, 2016) and other simulation studies (Bahlburg et al, 2021;Groeneveld et al, 2020;Hofmann & Lascara, 2000). The usage of these references for model validation is highlighted within the following section on state variables of each simulated entity as well as in the corresponding sections of the PEKRIS model code itself.…”

“…Therefore, it is important to understand how an increasing salp population might affect krill populations under different environmental conditions. Here, we linked two existing individual-based models, that simulate the life cycle and metabolism of a salp population (Groeneveld et al, 2020;Henschke et al, 2018) and the energy budget of krill (Bahlburg et al, 2021;Jager & Ravagnan, 2015). The name of the combined model PEKRIS stands for PErformance of KRIll vs. Salp.…”