Data from: Hypoxia threatens coral and sea anemone early life stages

Seawater hypoxia is increasing globally and can drive declines in
organismal performance across a wide range of marine taxa. However, the
effects of hypoxia on early life stages (e.g., larvae and juveniles) are
largely unknown, and it is unclear how evolutionary and life histories may
influence these outcomes. Here, we addressed this question by comparing
hypoxia responses across early life stages of three cnidarian species
representing a range of life histories: the reef-building coral Galaxea
fascicularis, a broadcast spawner with horizontal transmission of
endosymbiotic algae (family Symbiodiniaceae); the reef-building coral
Porites astreoides, a brooder with vertical endosymbiont transmission; and
the estuarine sea anemone Nematostella vectensis, a non-symbiotic
broadcast spawner. Transient exposure of larvae to hypoxia (dissolved
oxygen < 2 mg L-1 for 6 h) led to decreased larval swimming and
growth for all three species, which resulted in impaired settlement for
the corals. Coral-specific responses also included larval swelling,
depressed respiration rates, and decreases in symbiont densities and
function. These results indicate both immediate and latent negative
effects of hypoxia on cnidarian physiology and coral-algal mutualisms
specifically. In addition, G. fascicularis and P. astreoides were
sensitized to heat stress following hypoxia exposure, suggesting that the
combinatorial nature of climate stressors will lead to declining
performance for corals. However, sensitization to heat stress was not
observed in N. vectensis exposed to hypoxia, suggesting that this species
may be more resilient to combined stressors. Overall, these results
emphasize the importance of reducing anthropogenic carbon emissions to
limit further ocean deoxygenation and warming.