Quick Definition
A fish-specific property of haemoglobin in which a drop in pH reduces both the oxygen affinity AND the maximum oxygen capacity, enabling gas secretion into the swim bladder.
📖 Full Definition
The Root effect is a pH-sensitive property of teleost haemoglobin that goes beyond the normal Bohr effect. At low pH, Root-effect haemoglobins not only release oxygen more readily (Bohr effect) but also cannot be fully saturated with oxygen even at high partial pressures (reduced capacity). The acidified environment of the gas gland (produced by lactic acid secretion) exploits the Root effect to force oxygen off haemoglobin and into the gas phase, inflating the swim bladder against hydrostatic pressure. This is the only known mechanism capable of producing gas at pressures exceeding 300 atmospheres in deep-sea fish.
💡 Examples & Context
Deep-sea fish maintain swim bladder gas pressures equivalent to the ambient hydrostatic pressure — at 1000 m depth this is 100 atm, made possible by the Root effect working in concert with the rete mirabile of the gas gland.