Effects of hypoxia and hypercapnia on thermal tolerance: an integrative assessment on the green abalone (Haliotis fulgens).

• Main Author: Tripp Valdez, Miguel Angel
• Other Authors: Pörtner, Hans Otto, Hagen, Wilhelm
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2018
• Subjects: Climate change; green abalone; Thermal tolerance; Ecophysiology; OCLTT; 500; 500 Science; ddc:500; Baja; Pacific; Ocean acidification
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1564; https://nbn-resolving.org/urn:nbn:de:gbv:46-00107073-13

With the rise in atmospheric concentration of greenhouse gases, most marine ecosystems are facing increasing seawater temperatures, ocean acidification and a higher frequency or intensity of extreme warming events. Moreover, rising seawater temperature is expected to interact more frequently with falling oxygen levels (hypoxia) and increased CO2 concentration (hypercapnia). Both drivers may impose constraints on physiological mechanisms that define thermal Limits thereby increasing the vulnerability towards warming in marine ectotherms. The green abalone Haliotis fulgens is an economically important marine gastropod at the Pacific Coast of Mexico. In recent years, an increased frequency and intensity of environmental extremes, such as El Nino events and upwelling of highly hypoxic or hypercapnic water, has been associated with mass mortality events, threatening natural populations. Within this framework, the present study aimed at investigating the thermal tolerance and the underlying metabolic and molecular response in multiple tissues of H. fulgens under conditions of hypoxia and hypercapnia. Juvenile abalone (25.05 A /- 2.57 mm shell length) were exposed to a temperature ramp (from 18 degree Celsius to 32 degree Celsiu 3 degree Celsius day-1) under hypoxia (50% air saturation) and hypercapnia (a 1000 I atm PCO2), both individually and in combination; the conditions are based on natural oxygen declines occurring along the Baja California Peninsula and PCO2 values predicted by the end of the century, respectively. Hypoxia constrained the whole-organism oxygen consumption at moderate temperature (27 degree Celsius) paralleled by the accumulation of anaerobic metabolites (succinate, lactate, and alanine) in gill and hepatopancreas, suggesting a limitation in the aerobic capacity and reduced thermal tolerance. On the contrary, warming under hypercapnic exposure did not constrain Oxygen consumption, but the higher Q10 in metabolic rate and the increased levels of anaerobic metabolites at the warmest temperature (32 ...