Fast Changes in the Bioenergetic Balance of Krill in Response to Environmental Stress

Paulo F Lagos,Alva Curtsdotter,Amandine J M Sabadel,Miles D Lamare,Antonio Agüera,David J Burrit

doi:10.3389/fmars.2021.782524

Abstract

A Dynamic Energy Budget (DEB) model is applied to predict rapid metabolic shifts in an ecologically important krill, Nyctiphanes australis, in response to temperature and ultraviolet radiation (UVR). Specifically, we predict changes in fatty acids, amino acids and respiration rate in response to several light and temperature treatments. Environmental variability can alter the metabolic equilibrium and the mechanisms marine ectotherms used to obtain energy, which is a topical point given the current level of environmental change. Environmental variability also includes multiple stressors, which can have additive, antagonistic or synergistic effects on metabolism. In consequence, disentangling and quantifying the effects of multiple stressors on metabolism and the energy balance of ecthothermal species, such as krill, can be challenging. Here we apply a DEB model to direct measurements of fatty acids, amino acids and respiration rate of krill experimentally exposed simultaneously to several doses of UVR and temperatures. We found that on average light escalates metabolic rates by a factor of two, and temperature has an effect 1.35 times greater than the effect of light over respiration rates at temperatures from 9 to 19°C. The DEB model predicted shifts in metabolic function and indicated that the combined effect of light and elevated temperatures decrease the total of fatty acid concentrations at a higher rate than amino acids when krill are exposed to environmentally relevant temperatures and light treatments. Our results demonstrate that, when krill experience warmer conditions and higher levels of solar radiation, the mobilization of energy-relevant metabolites from the reserves increases by up to 36% and increase the total energetic cost by up to 45%. These findings suggest that ectothermal species with a fast metabolism, such as krill, quickly deplete energy reserves to compensate for changes in the environment. This renders krill susceptible to the effects of climate variability if the current climatic trend for the region continues to show temperature increases, even if solar radiation levels remain unchanged.

Highlights

Variability in the marine environment, such as in temperature and ultraviolet radiation (UVR), present challenges for marine ectotherms, which frequently need to survive adverse abiotic conditions caused by multiple stressors
The Dynamic Energy Budget (DEB) model successfully predicted the rate of decrease of fatty acids (FAs) in time, with error estimates for the predicted decrease of FAs in time ranging between MRE = 0.05–0.33 (Figure 3) and error estimates for the decrease of amino acids (AAs) in time ranging between MRE = 0.02–0.48 (Figure 5)
This rate of decrease was greater when doses of UVR are above 31 J cm−2 UVA and 3.2 J cm−2 UVB and when the temperature is above 16◦C, slowing down at temperatures below 16◦C

Summary

Introduction

Variability in the marine environment, such as in temperature and ultraviolet radiation (UVR), present challenges for marine ectotherms, which frequently need to survive adverse abiotic conditions caused by multiple stressors. This is especially true when shifts in distribution or behavior are insufficient to mitigate the increased levels of stress created by global climate change (Sokolova, 2021). Processbased modeling approaches, informed by empirical data, can be powerful tools to explore biological mechanisms We take such an approach to gain insight into the metabolic response of krill exposed to multiple environmental stressors

Methods

Results

Conclusion