Exposure to extreme hypercapnia under laboratory conditions does not impact righting and covering behavior of juveniles of the common sea urchin Lytechinus variegatus

Abstract

Changes in the carbonate chemistry (increased pCO2, decreased pH, and decreased carbonate saturation state) of seawater can impact the growth and physiology of echinoids and therefore, it is possible that their behavior may also be negatively affected. We investigated the impact of extreme hypercapnia on righting activity and covering response in juvenile Lytechinus variegatus (avg. diameter = 20 mm) raised in artificial seawater. Sea urchins collected from Eagle Harbor in Saint Joseph Bay, Florida (29°N, 85°W), were exposed to high pCO2 conditions, (pCO2 = 1738 ± 25.00 μatm, and pHNBS = 7.7 ± 0.002) for three months under subsatiation conditions. Righting activity (time to right to 90° position from inversion) was evaluated every three weeks and was not significantly different between treatments (repeated measures ANOVA, F = 0.84896, df = 1, 22, and p = 0.36684). At the end of the study, covering behavior (% surface area of the test covered with acrylic beads) was also not significantly different from those individuals raised under control conditions (pCO2 = 608 ± 12.00 μatm, pHNBS = 8.1 ± 0.004; and nonparametric repeated measures ANOVA, χ 2 = 1.2831, df = 1, and p = 0.25732). These results suggest that juvenile and young adult L. variegatus behavior is not altered under conditions of extreme hypercapnia. These findings are particularly relevant to future studies on the basic and applied biology of sea urchins that employ the use of artificial sea salts.