No maternal or direct effects of ocean acidification on egg hatching in the Arctic copepod Calanus glacialis.

Peter Thor,Marie-Helene Carignan,Sarah Jacque,Fanny Vermandele,Piero Calosi,Erik V Thuesen

doi:10.1371/journal.pone.0192496

Peter Thor, Marie-Helene Carignan + Show 4 more

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https://doi.org/10.1371/journal.pone.0192496

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Abstract

Widespread ocean acidification (OA) is transforming the chemistry of the global ocean and the Arctic is recognised as the region where this transformation will occur at the fastest rate. Moreover, many Arctic species are considered less capable of tolerating OA due to their lower capacity for acid-base regulation. This inability may put severe restraints on many fundamental functions, such as growth and reproductive investments, which ultimately may result in reduced fitness. However, maternal effects may alleviate severe effects on the offspring rendering them more tolerant to OA. In a highly replicated experiment we studied maternal and direct effects of OA predicted for the Arctic shelf seas on egg hatching time and success in the keystone copepod species Calanus glacialis. We incubated females at present day conditions (pHT 8.0) and year 2100 extreme conditions (pHT 7.5) during oogenesis and subsequently reciprocally transplanted laid eggs between these two conditions. Statistical tests showed no effects of maternal or direct exposure to OA at this level. We hypothesise that C. glacialis may be physiologically adapted to egg production at low pH since oogenesis can also take place at conditions of potentially low haemolymph pH of the mother during hibernation in the deep.

Highlights

Uptake of anthropogenic CO2 is changing the chemistry of the global ocean [1]
Individuals were identified to species by number of pleopods and abdominal segments. They were distinguished from C. finmarchicus and C. hyperboreus on the basis of size [28], the presence of red pigmentation in the antennules, a characteristic distinguishing C. glacialis from C. finmarchicus [42], and the lack of lateral spikes on the distal prosome segment, which is a characteristic of C. hyperboreus
There were no significant difference among the four treatment groups in egg hatching success (EHS) (1-factor PERMANOVA: Treatment group: Pseudo-F3,93 = 0.44, P = 0.72, transplant Pseudo-F32,93 = 0.99, P = 0.51) (Table 2)

Summary

Introduction

CO2 reacts with water to form carbonic acid, and this ocean acidification (OA) has lowered the global ocean mean surface pH from 8.13 during the pre-industrial age to the present day 8.05. This trend is predicted to continue and current models estimate a further decrease of up to 0.4 pH units by the year 2100 [2,3,4].

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