Variable metabolic responses of Skagerrak invertebrates to low O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and high CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; scenarios

Aisling Fontanini,Alexandra Steckbauer,Sam Dupont,Carlos M Duarte

doi:10.5194/bg-15-3717-2018

Abstract

Abstract. Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time, we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation; however, the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats, such as sand and mud flats, seagrass beds, exposed and protected shorelines and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high or low oxygen and low or high CO2; varying pCO2 of 450 and 1300 µatm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allowed us to evaluate respiration responses of species of contrasting habitats to single and multiple stressors. Results show that respiratory responses were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will result in multiplicative effects and focus attention on alleviating hypoxia in the region.

Highlights

Resolving the responses of marine organisms to the multiple pressures associated with global change is a major challenge for marine scientists (Duarte et al, 2014)
Responses to low O2 and elevated pCO2 were variable amongst phyla and species in the community tested here, ranging from antagonistic to synergistic responses
Respiratory responses to low O2 and elevated pCO2 were variable amongst phyla and species in the community tested here, ranging from buffered to amplified metabolic responses

Summary

Introduction

Resolving the responses of marine organisms to the multiple pressures associated with global change is a major challenge for marine scientists (Duarte et al, 2014). This challenge is pressing for coastal ecosystems, where human populations and impacts often concentrate. Among these pressures, decreasing O2 concentrations (hypoxia) and ocean acidification (OA) are receiving particular attention (Diaz and Rosenberg, 2008; Vaquer-Sunyer and Duarte, 2008; Doney et al, 2009; Kroeker et al, 2013). Hypoxia is affecting a growing number of coastal ecosystems (Diaz and Rosenberg, 2008; Vaquer-Sunyer and Duarte, 2008), suggesting that eutrophication-driven acidification (Borges and Gypens, 2010; Cai et al, 2011) should be spreading as well

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Discussion

Conclusion