Ocean acidification challenges copepod phenotypic plasticity

Anu Vehmaa,Anna-Karin Almén,Sara Furuhagen,Andreas Brutemark,Allanah Paul,Jonna Engström-Öst,Ulf Riebesell

doi:10.5194/bg-13-6171-2016

Abstract

Abstract. Ocean acidification is challenging phenotypic plasticity of individuals and populations. Calanoid copepods (zooplankton) are shown to be fairly plastic against altered pH conditions, and laboratory studies indicate that transgenerational effects are one mechanism behind this plasticity. We studied phenotypic plasticity of the copepod Acartia sp. in the course of a pelagic, large-volume mesocosm study that was conducted to investigate ecosystem and biogeochemical responses to ocean acidification. We measured copepod egg production rate, egg-hatching success, adult female size and adult female antioxidant capacity (ORAC) as a function of acidification (fCO2 ∼ 365–1231 µatm) and as a function of quantity and quality of their diet. We used an egg transplant experiment to reveal whether transgenerational effects can alleviate the possible negative effects of ocean acidification on offspring development. We found significant negative effects of ocean acidification on adult female size. In addition, we found signs of a possible threshold at high fCO2, above which adaptive maternal effects cannot alleviate the negative effects of acidification on egg-hatching and nauplii development. We did not find support for the hypothesis that insufficient food quantity (total particulate carbon < 55 µm) or quality (C : N) weakens the transgenerational effects. However, females with high-ORAC-produced eggs with high hatching success. Overall, these results indicate that Acartia sp. could be affected by projected near-future CO2 levels.

Highlights

Increased concentrations of carbon dioxide (CO2) in the atmosphere is changing the carbon chemistry of the world’s oceans
Females with high-ORAC-produced eggs with high hatching success. These results indicate that Acartia sp. could be affected by projected near-future CO2 levels
Our results indicate that Acartia sp. reproduction is sensitive to ocean acidification, no f CO2 effect was found for the abundance of this species (Lischka et al, 2015)

Summary

Introduction

Increased concentrations of carbon dioxide (CO2) in the atmosphere is changing the carbon chemistry of the world’s oceans. CO2 dissolves in seawater, thereby decreasing ocean pH. Ocean acidification is increasing fast and pH is expected to decrease by a further 0.14–0.43 pH units during the coming century (IPCC, 2007). Acidification can cause various problems to biochemical and physiological processes in aquatic organisms. Populations can respond in three main ways: through plastic responses of individuals, through genetic changes across generations or through escaping in space or time by modification of phenology. Phenotypic plasticity, i.e. the ability of an individual or a population to alter its physiological state, appearance or behaviour in response to the environment, is of major importance (West-Eberhard, 2003).

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Discussion

Conclusion