Impact of ocean acidification on the hypoxia tolerance of the woolly sculpin, Clinocottus analis.

Joshua R Hancock,Sean P Place

doi:10.1093/conphys/cow040

Abstract

As we move into the Anthropocene, organisms inhabiting marine environments will continue to face growing challenges associated with changes in ocean pH (ocean acidification), dissolved oxygen (dead zones) and temperature. These factors, in combination with naturally variable environments such as the rocky intertidal zone, may create extreme physiological challenges for organisms that are already performing near their biological limits. Although numerous studies have examined the impacts of climate-related stressors on intertidal animals, little is known about the underlying physiological mechanisms driving adaptation to ocean acidification and how this may alter organism interactions, particularly in marine vertebrates. Therefore, we have investigated the effects of decreased ocean pH on the hypoxia response of an intertidal sculpin, Clinocottus analis. We used both whole-animal and biochemistry-based analyses to examine how the energetic demands associated with acclimation to low-pH environments may impact the fish's reliance on facultative air breathing in low-oxygen environments. Our study demonstrated that acclimation to ocean acidification resulted in elevated routine metabolic rates and acid-base regulatory capacity (Na+,K+-ATPase activity). These, in turn, had downstream effects that resulted in decreased hypoxia tolerance (i.e. elevated critical oxygen tension). Furthermore, we present evidence that these fish may be living near their physiological capacity when challenged by ocean acidification. This serves as a reminder that the susceptibility of teleost fish to changes in ocean pH may be underestimated, particularly when considering the multiple stressors that many experience in their natural environments.

Highlights

Driven global climate change is fundamentally altering ocean environments at an alarming rate (Doney et al, 2009)
Temperature, salinity and total alkalinity remained constant over the course of both experiments, with only pH and PCO2 varying based on desired treatment levels (Table 1)
Our study examined how intertidal woolly sculpins were affected by exposure to differing levels of acidification coupled with environmental hypoxia

Summary

Introduction

Driven global climate change is fundamentally altering ocean environments at an alarming rate (Doney et al, 2009). In the past 50 years alone, average global temperatures have increased by ~0.6°C (Walther et al, 2002), while oceanic carbon dioxide sequestration has occurred at a rate 100 times greater than at any time in the past 650 000 years (Siegenthaler et al, 2005). The intergovernmental panel on climate change (IPCC) predicts that by the year 2100, our oceans could decrease in pH by 0.3–0.4 units, corresponding to a partial pressure of carbon dioxide (PCO2) upwards of 1000 μatm (IPCC, 2013). As we monitor these broad-scale environmental changes, it becomes apparent that marine organisms are, and.

Methods

Results

Discussion

Conclusion