Aerobic performance of two tropical cephalopod species unaltered by prolonged exposure to projected future carbon dioxide levels.

Blake L Spady,Tiffany J Nay,Sue-Ann Watson,Philip L Munday,Jodie L Rummer

doi:10.1093/conphys/coz024

Abstract

Squid and many other cephalopods live continuously on the threshold of their environmental oxygen limitations. If the abilities of squid to effectively take up oxygen are negatively affected by projected future carbon dioxide (CO2) levels in ways similar to those demonstrated in some fish and invertebrates, it could affect the success of squid in future oceans. While there is evidence that acute exposure to elevated CO2 has adverse effects on cephalopod respiratory performance, no studies have investigated this in an adult cephalopod after relatively prolonged exposure to elevated CO2 or determined any effects on aerobic scope. Here, we tested the effects of prolonged exposure (≥20% of lifespan) to elevated CO2 levels (~1000μatm) on the routine and maximal oxygen uptake rates, aerobic scope and recovery time of two tropical cephalopod species, the two-toned pygmy squid, Idiosepius pygmaeus and the bigfin reef squid, Sepioteuthis lessoniana. Neither species exhibited evidence of altered aerobic performance after exposure to elevated CO2 when compared to individuals held at control conditions. The recovery time of I. pygmaeus under both control and elevated CO2 conditions was less than 1hour, whereas S. lessoniana required approximately 8hours to recover fully following maximal aerobic performance. This difference in recovery time may be due to the more sedentary behaviours of I. pygmaeus. The ability of these two cephalopod species to cope with prolonged exposure to elevated CO2 without detriment to their aerobic performance suggests some resilience to an increasingly high CO2 world.

Highlights

Atmospheric carbon dioxide (CO2) concentrations have increased from 280 ppm before the industrial revolution to over 400 ppm in the current day (Dlugokencky and Tans, 2018), a level that is higher than any time in the past 800 000 years (Lüthi et al, 2008)
The aerobic scope of pygmy squid was similar between CO2 treatments, with an average of 746 ± 52 mg kg−1 h−1 at control compared to 776 ± 49 mg kg−1 h−1 under elevated CO2 (x2 = 0.929, df = 14, P = 0.335) (Fig. 2A)
The responses observed here under elevated CO2 differ from the reduction in M O2Max and M O2Routine observed in the jumbo squid (Rosa and Seibel, 2008) and the decrease in oxygen uptake rates observed in the common cuttlefish and European squid during late-stage embryo incubation (Rosa et al, 2014; Sigwart et al, 2016)

Summary

Introduction

Atmospheric carbon dioxide (CO2) concentrations have increased from 280 ppm before the industrial revolution to over 400 ppm in the current day (Dlugokencky and Tans, 2018), a level that is higher than any time in the past 800 000 years (Lüthi et al, 2008). The increase in average pCO2 along with the amplification of seasonal cycles of pCO2 indicates that marine organisms could experience CO2 levels >1000 μatm before the end of the century (McNeil and Sasse, 2016). This rapid increase of CO2 levels in the surface oceans could have a range of adverse effects on many marine species (Hoegh-Guldberg et al, 2007; Fabry et al, 2008; Doney et al, 2009; Kroeker et al, 2013; Clements and Hunt, 2015; Cattano et al, 2018)

Results

Discussion

Conclusion