Physiological and behavioral responses of the copepod Temora turbinata to hypoxia

Hypoxia is intensified in tropical and subtropical estuarine and coastal waters and brings about lethal and sublethal effects to marine copepods. The physiological and behavioral responses of the subtropical calanoid copepod Temora turbinata were tested after short-term exposure to hypoxia. The LD₅₀ values were 3.02 ± 0.21, 2.00 ± 0.35, and 3.11 ± 0.31 mg L^-1 for nauplii (II-III), copepodites (II-III), and female adults, respectively. With a decrease in the ambient dissolved oxygen (DO) level from 8 to 0.5 mg L^-1, the ingestion rates decreased significantly at all life stages, as did oxygen consumption in female adults. In an artificial stratification column with a DO gradient, female adults exhibited an obvious avoidance response to the hypoxic bottom layer. Our study provides preliminary evidence for high hypoxia sensitivity in T. turbinata and implies that the DO level may be the main factor controlling the distribution of this species in tropical and subtropical coastal and estuarine waters.