Can niche plasticity mediate species persistence under ocean acidification?

Global change stressors can modify ecological niches of species, and hence
alter ecological interactions within communities and food webs. Yet, some
species might take advantage of a fast-changing environment, and allow
species with high niche plasticity to thrive under climate change. We used
natural CO2 vents to test the effects of ocean acidification on niche
modifications of a temperate rocky reef fish assemblage. We quantified
three ecological niche traits (overlap, shift, and breadth) across three
key niche dimensions (trophic, habitat, and behavioural). Only one species
increased its niche width along multiple niche dimensions (trophic and
behavioural), shifted its niche in the remaining (habitat), and was the
only species to experience a highly increased density (i.e. doubling) at
vents. The other three species that showed slightly increased or declining
densities at vents only displayed a niche width increase in one (habitat
niche) out of seven niche metrics considered. This niche modification was
likely in response to habitat simplification (transition to a system
dominated by turf algae) under ocean acidification. We further show that
at the vents, the less abundant fishes have a negligible competitive
impact on the most abundant and common species. Hence, this species
appears to expand its niche space overlapping with other species,
consequently leading to lower abundances of the latter under elevated CO2.
We conclude that niche plasticity across multiple dimensions could be a
potential adaptation in fishes to benefit from a changing environment in a
high-CO2 world.