Elevated CO2 and food ration affect growth but not the size-based hierarchy of a reef fish

Shannon J Mcmahon,Jennifer M Donelson,Philip L Munday,Marian Y L Wong

doi:10.1038/s41598-019-56002-z

Shannon J Mcmahon, Jennifer M Donelson + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-56002-z

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Abstract

Under projected levels of ocean acidification, shifts in energetic demands and food availability could interact to effect the growth and development of marine organisms. Changes to individual growth rates could then flow on to influence emergent properties of social groups, particularly in species that form size-based hierarchies. To test the potential interactive effects of (1) food availability, (2) elevated CO2 during juvenile development, and (3) parental experience of elevated CO2 on the growth, condition and size-based hierarchy of juvenile fish, we reared orange clownfish (Amphiprion percula) for 50 days post-hatching in a fully orthogonal design. Development in elevated CO2 reduced standard length and weight of juveniles, by 9% and 11% respectively, compared to ambient. Development under low food availability reduced length and weight of juveniles by 7% and 15% respectively, compared to high food. Parental exposure to elevated CO2 restored the length of juveniles to that of controls, but it did not restore weight, resulting in juveniles from elevated CO2 parents exhibiting 33% lower body condition when reared in elevated CO2. The body size ratios (relative size of a fish from the rank above) within juvenile groups were not affected by any treatment, suggesting relative robustness of group-level structure despite alterations in individual size and condition. This study demonstrates that both food availability and elevated CO2 can influence the physical attributes of juvenile reef fish, but these changes may not disrupt the emergent group structure of this social species, at least amongst juveniles.

Highlights

Under projected levels of ocean acidification, shifts in energetic demands and food availability could interact to effect the growth and development of marine organisms
Juveniles from control CO2 treatment parents that developed in the elevated CO2 conditions were 9% shorter compared to siblings that developed at control CO2 (Table S6)
The growth and physical condition of juvenile fish is critical to their performance and survival[63,64,65,66], yet how these traits are affected by the environmental conditions experienced during early life, and the conditions experienced by their parents, is still poorly understood

Summary

Introduction

Under projected levels of ocean acidification, shifts in energetic demands and food availability could interact to effect the growth and development of marine organisms. To test the potential interactive effects of (1) food availability, (2) elevated CO2 during juvenile development, and (3) parental experience of elevated CO2 on the growth, condition and size-based hierarchy of juvenile fish, we reared orange clownfish (Amphiprion percula) for 50 days post-hatching in a fully orthogonal design. Recent research has shown that elevated CO2 exposure results in reduced growth and survival during the early life history of some fishes[19,20,21,22,23], possibly due to increased energetic costs of cellular processes. Size-based social hierarchies are typically behaviourally regulated, with subordinate individuals limiting their food intake and regulating their growth in order to maintain the appropriate body size ratio in relation to the fish in the social hierarchy[33]. The diversity of responses previously observed when both parents and their offspring experience elevated CO2 conditions highlights the need for further research to understand how parental effects may influence offspring performance in future projected ocean conditions, especially when food resources are limited

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