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Abstract

Adult sea urchins, Anthocidaris crassispina, were reared individually in running seawater equilibrated with gas mixtures containing 380 ppm (control), 1,000 ppm or 3,000 ppm CO2, at ambient natural temperature for 140 days to study effects of elevated CO2 on feed intake, fecal production, oxygen consumption, and the morphology of Aristotle’s lantern. Feed intake became significantly lower in the two high CO2 groups than in the control after 90 (1,000 ppm) or 110 (3,000 ppm) days and remained suppressed until the end of the experiment (control, 0.16 ± 0.01 (mean ± SE) g dry wt ind-1 day-1; 1,000 ppm, 0.10 ± 0.01; 3,000 ppm, 0.11 ± 0.01, as determined on day 140). Fecal production showed similar responses. Oxygen consumption was 35% lower in the two high CO2 groups when measured on day 50, but subsequently became similar between the groups except a significant difference between control and 3,000 ppm urchins on day 140. When determined on day 140, magnesium concentration of the coelomic fluid was significantly elevated, but calcium concentration was unaffected in the high CO2 urchins. Exposure to 3,000 ppm CO2 resulted in undulating lateral plates and ridges of the teeth, and the distal edges of tooth ridges appeared worn out. These results suggest that energy available for growth and reproduction was compromised under the elevated CO2 conditions, which might lead to reduced growth and reproductive output when exposure prolonged.

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