Mangrove fishes rely on emersion behavior and physiological tolerance to persist in sulfidic environments

We report the presence of fishes (Kryptolebias marmoratus, Poecilia orri, Gambusia sp., and Dormitator maculatus) in Belizean mangrove pools with extremely high H2S concentrations (up to 1,166 mM) that would be lethal for most fishes. Thus, we asked whether the three most prevalent species (Kryptolebias, Poecilia, and Gambusia) persist in sulfidic pools because they are exceptionally H2S tolerant and/or because they can leave water (emerse) and completely avoid H2S.

We show that both physiological tolerance and emersion behavior are important. Kryptolebias demonstrated high H2S tolerance, as they lost equilibrium significantly later than Poecilia and Gambusia during H2S exposure (1,188 +/- 21 mM H2S). However, the fact that all species lost equilibrium at an ecologically relevant [H2S] suggests that physiological tolerance may suffice at moderate H2S concentrations but that another strategy is required to endure higher concentrations.