Acidification reduced growth rate but not swimming speed of larval sea urchins

Abstract

Swimming behaviors of planktonic larvae impact dispersal and population dynamics of many benthic marine invertebrates. This key ecological function is modulated by larval development dynamics, biomechanics of the resulting morphology, and behavioral choices. Studies on ocean acidification effects on larval stages have yet to address this important interaction between development and swimming under environmentally-relevant flow conditions. Our video motion analysis revealed that pH covering present and future natural variability (pH 8.0, 7.6 and 7.2) did not affect age-specific swimming of larval green urchin Strongylocentrotus droebachiensis in still water nor in shear, despite acidified individuals being significantly smaller in size (reduced growth rate). This maintenance of speed and stability in shear was accompanied by an overall change in size-corrected shape, implying changes in swimming biomechanics. Our observations highlight strong evolutionary pressure to maintain swimming in a varying environment and the plasticity in larval responses to environmental change.

Near-future ocean acidification impacts maintenance costs in sea-urchin larvae: Identification of stress factors and tipping points using a DEB modelling approach

“…Interestingly, the data of Stumpp et al (2013) show a higher stress level around pH = 7.3 than the data sets of Dorey et al (2013) and Chan et al (2015); the latter two being in close correspondence. The data of Stumpp et al (2013) also yielded quite different parameter estimates from the other two studies (Table 1).…”

“…The data for sea-urchin larvae, however, offer some tantalising clues to a more flexible view of maintenance. The difference in growth pattern in the reference treatments for the studies of Dorey et al (2013) and Chan et al (2015) on the one hand, and those of Stumpp et al (2013) on the other, can largely be explained by a smaller egg size and lower maintenance needs in the latter study. Furthermore, as discussed, the negative effects of OA on growth may have been partly compensated, later in larval development, by reducing basal maintenance needs.…”

“…Data were taken from the studies published in Dorey et al (2013); Stumpp et al (2013) and Chan et al (2015), which used the same methodologies. Briefly, adult urchins were spawned and gametes fertilized.…”

“…For each replicated aquarium, an average pH was calculated (Chan et al, 2015;Dorey et al, 2013;Stumpp et al, 2013). We fitted each individual replicate with its own stress factor (stress was set to zero for one arbitrary replicate in the pH 8.1 treatment).…”

Peer Review #2 of "Ontogenetic changes in swimming speed of silver carp, bighead carp, and grass carp larvae: implications for larval dispersal (v0.2)"

“…This should be expanded on in future experiments to determine the role 383 that abiotic factors can play in larval swimming capacity. Other water quality parameters, 384 such as pH and turbidity, can also influence larval swimming behavior (Rieger and 385 Summerfelt 1997; Utne-Palm 2004; Chan et al 2015) and should also be considered for 428 1988). While vertical distribution of larvae in the water column is unknown, this shows 429 that at least a portion of larvae can use the fastest currents near the surface, potentially 430 expanding their downstream dispersal range.…”