This study has demonstrated that spikes in water temperature
that occur at low tide affect photosynthesis of tropical seagrasses
and, that, if occurring on successive days (6 days) can lead to
declines in seagrass growth and increased mortality. Temperature
spikes in the order of 35–43 C occurred during 2008–2012 for
intertidal meadows of the northern Great Barrier Reef, becoming
rarer at higher temperatures. The effect of temperature spikes
when experimentally tested went from positive photosynthetic
efficiency (but no effect on growth) at 35 C to strongly negative
(complete mortality) at 43 C. The implication of these findings is
that the rare, but occasional events when water temperature
exceeds 40 C will have a significant effect on intertidal seagrass
meadows and result in mortality