Metabolic scope and hypoxia tolerance of Atlantic croaker (Micropogonias undulatus Linnaeus, 1766) and spot (Leiostomus xanthurus Lacepède, 1802), with insights into the effects of acute temperature change

Abstract

Dynamic conditions in estuaries result in fish experiencing acute changes in temperature and oxygen levels, the magnitude of which are predicted to increase due to directional climate change. Acute changes in temperature impose physiological stress on individuals through alterations in metabolism (often quantified as aerobic metabolic scope) that affect growth, reproduction, movement, and hypoxia tolerance; and their magnitude can thus have population-level consequences. Furthermore, increases in the magnitude of acute changes in temperature and oxygen levels in estuaries may reduce the availability of suitable habitat. We used intermittent-flow respirometry to determine the effects of acute temperature changes on the metabolic scope and hypoxia tolerance of Atlantic croaker and spot; two economically and ecologically important species in Chesapeake Bay. For Atlantic croaker, metabolic scope increased from 15 to 25 °C but did not change from 25 to 30 °C, whereas metabolic scope increased from 15 to 30 °C for spot. The metabolic scope of Atlantic croaker and spot was comparable at all temperatures examined. Hypoxia tolerance, and the effects of temperature on hypoxia tolerances, did not differ by species. Our results indicate that Atlantic croaker and spot are well-adapted to the conditions they currently experience in Chesapeake Bay. Decreased availability of suitable habitat as environmental conditions continue to change will, however, result in increased competition for resources. Our results suggest that under these conditions, spot will have a competitive advantage over Atlantic croaker which may alter the dynamics of the Chesapeake Bay ecosystem.