Thermal tolerance of Arbacia lixula

As the ocean warms, the thermal tolerance of marine invertebrates is key
to determining their distributional change, where acclimation to low pH
may impact the thermal range of optimal development. We compared thermal
tolerance of progeny from a low pH-acclimated sea urchin (Arbacia lixula)
population from the CO2 vents of Ischia (Italy), and a nearby population
living at ambient pH. The percentage of normally developing gastrulae and
two-armed larvae were determined across 10 temperatures representing
present and future temperature conditions (16-34 ˚C). Vent-acclimated sea
urchins showed a greater percentage of normal development at 24 hours,
with a larger optimal developmental temperature range than control sea
urchins (12.3 ˚C vs 5.4 ˚C range, respectively). At 48 hours, upper lethal
temperatures for 50% survival with respect to ambient temperatures were
similar between control (+6.8 ˚C) and vent (+6.2 ˚C) populations. Thus,
acclimation to low pH did not impact the broad thermal tolerance of A.
lixula progeny. With A. lixula’s barrens forming abilities, its wide
thermotolerance and its ability to acclimate to low pH, this species will
continue to be an important ecological engineer in Mediterranean
macroalgal ecosystems in a changing ocean.