2
$\begingroup$

How do high concentrations of carbon dioxide suffocate fish?

It is common knowledge in fishkeeping that high concentrations of carbon dioxide are harmful to and can even kill fish. I am trying to understand why.

One explanation is that carbon dioxide displaces oxygen in water. However, this doesn't have much scientific basis, as different gases that don't react with each other do not affect each other’s solubility.

Another factor is that carbon dioxide reduces the pH of water by producing carbonic acid, but to y knowledge fish seem generally able to tolerate wide ranges of pH according to many studies done on the topic.

So there must be another reason that carbon dioxide suffocates fish.

Improve this question
$\endgroup$
1
  • $\begingroup$ I've found several studies indicating that hypercapnia induces hyperventilation in fish. Hyperventilation is bad in mammals, so I wonder if this is the pathway for harm to fish in hypercapnic conditions. $\endgroup$
    – Patrick
    Commented Aug 2 at 18:00

1 Answer 1

Reset to default
2
$\begingroup$

Elevated CO2 levels in aquatic environments pose significant threats to fish physiology and behavior. Fish are particularly vulnerable to increased CO2 due to their small PCO2 gradient between body fluids and the environment (Ishimatsu et al., 2005). High CO2 concentrations impair vital functions such as respiration, circulation, and metabolism, potentially reducing growth rates and population sizes (Ishimatsu et al., 2005). Moreover, elevated CO2 levels compromise the olfactory system of marine fish, reducing their ability to detect odors and respond to sensory cues (Porteus et al., 2018). This impairment is linked to suppressed transcription of genes involved in synaptic strength and cell excitability in the olfactory system (Porteus et al., 2018). The underlying mechanism of behavioral disruptions is associated with alterations in ion gradients across the GABAA receptor, which is responsible for inhibitory input in neural circuits (Heuer et al., 2019). These physiological changes ultimately increase mortality and affect fish survival in high-CO2 environments (Amador, 2018).

Improve this answer
$\endgroup$
5
  • 1
    $\begingroup$ Thanks, the Ishimatsu paper seems to be very promising in its description of the mechanism by which CO2 causes harm to fish. I'm having trouble finding the Amador paper - can you share the title of it? $\endgroup$
    – Patrick
    Commented Aug 2 at 18:32
  • $\begingroup$ I think I found it. "Sea bass (can't) smell trouble under elevated CO2" $\endgroup$
    – Patrick
    Commented Aug 2 at 18:53
  • 2
    $\begingroup$ First author and year are not a sufficient citation, please update to include enough information to identify the source. $\endgroup$
    – Bryan Krause ♦
    Commented Aug 2 at 19:47
  • 1
    $\begingroup$ Could it be that high CO2 levels would reduce the O2 binding by the hemoglobin in the gills? leading to asphyxia? $\endgroup$
    – heracho
    Commented Aug 2 at 19:47
  • $\begingroup$ @heracho Yes, the Ishimatsu paper "Physiological effects on fishes in a high-CO2 world" mentions the Bohr and Root effects which reduces the ability of O2 to bind to hemoglobin. In the scenarios tested, the fish could satisfy oxygen demands when not moving. Some fish exhibited a significant decrease in ability to consume oxygen, while other more hardy ones did just fine. $\endgroup$
    – Patrick
    Commented Aug 2 at 20:58

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .