Events causing bodies of water to become hypoxic (low oxygen levels) are increasing with climate change. Water can become hypoxic when it warms up or there are changes in tidal flow, density, wind patterns as well as separation from the main source, such as occurs in a tidepool. While some fish are tolerant of hypoxia and even anoxia (oxygen depleted) environments others, such as Atlantic cod and steelhead trout, rely on oxygen to meet metabolic demands.
A new study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology explored why steelhead trout (Oncorhynchus mykiss) that have acclimated to hypoxic ‘warm’ water (13-14 degC) for 2-3 months are not able to pump as much blood out of the heart with each heart beat. What they found was that the heart muscle of these hypoxia-intolerant fish was not able to contract as well after adapting to hypoxic conditions. In addition, the fish exposed to hypoxic warm water weighed 20% less than fish accustomed to water with normal oxygen concentrations.
C Carnevale, JC Roberts, DA Syme, AK Gamperl. Hypoxic acclimation negatively impacts the contractility of steelhead trout (Oncorhynchus mykiss) spongy myocardium. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. 20 NOV 2019 https://doi.org/10.1152/ajpregu.00107.2019