Meeting Abstract

72.3  Monday, Jan. 6 08:30  Ocean acidification alters energy allocation in developing sea urchins PAN, F.*; APPLEBAUM, S.L.; SAWYER, R.J.; MANAHAN, D.T.; Univ. of Southern California; Univ. of Southern California; Univ. of Southern California; Univ. of Southern California tienchip@usc.edu

Ocean acidification (OA) is known to have dose- and species-specific impacts on developmental stages of marine invertebrates. While many species appear capable of withstanding the stress of OA, less is understood about the mechanisms underlying the metabolic basis of resilience. We studied changes in energy (ATP) allocation for the two major physiological processes that regulate metabolism in developing sea urchins – protein synthesis and ion regulation (Na⁺, K⁺-ATPase). During the first two weeks of development, metabolic responses were investigated under present-day (380 ppm) and near-future (800 ppm) CO₂ levels in seawater. Acidification treatment had little effect on size, biochemical composition, or physiological rates in pre-feeding stages (1-4 days post-fertilization). For later stages, the effect of OA on size and metabolic rate was absent or remained small; however, absolute rates of protein synthesis and in vivo ion pump activity increased. For same-sized larvae with similar metabolic rates, OA treatment resulted in a doubling of the proportion of ATP allocated to protein synthesis and ion transport (in some cases, more than 90% of available ATP). Our results show that while growth and morphological characteristics remain minimally impacted by OA, studies limited to those levels of biological analysis do not reveal the major mechanisms of response to OA. It is instead the major changes in rate processes at the biochemical level that result in differential allocation of ATP in response to OA. Biological variance in the ability of organisms to re-allocate energy usage, while still remaining within the tightly constrained available pool of total ATP, will likely establish the resilience of organisms to respond to OA and other stressors under natural conditions.