Ocean Acidification and Fish Respiration: A Study on the Anatomical, Physiological, and Behavioral Adaptations of Fishes and Their Ability to Cope With Decreasing Seawater PH

• Main Author: Rogers, Mark P.
• Format: Text
• Language: unknown
• Published: NSUWorks 2020
• Subjects: Climate Change; Ocean Acidification; Fish Respiration; Vascular Corrosion Casting; Mercox II; Coronary Circulation; Blood Oxygen Content; Animal Sciences; Biology; Marine Biology; Ocean acidification
• Online Access: https://nsuworks.nova.edu/hcas_etd_all/25; https://nsuworks.nova.edu/context/hcas_etd_all/article/1025/viewcontent/auto_convert.pdf

Abstract Fish stocks across the globe are increasingly being relied upon to supply the ever-growing human population with high quality protein and other nutrients. In addition to fishing pressure, stressors brought on by climate changes, including ocean acidification and hypoxic conditions, have the potential for providing substantial negative impacts on the efficiency of fish respiration, internal acid-base balance, and energy budgets. To meaningfully integrate the potential impacts of ocean acidification on fishes into management practices it is important to study the anatomical, physiological, and behavioral adaptations that enable fish to cope with decreasing seawater pH and how those mechanisms might be coupled with the functioning of the circulatory system. The current average seawater pH is between 8.4 and 8.1. Climate modeling statistics, based on past and projected anthropogenic CO² output, have estimated that at current CO2 output trajectories we will see average seawater pH values around 7.8 by the year 2100, 7.6 by the year 2200 and potentially as low as 7.45 by the year 2300. Most marine fishes maintain internal pH homeostasis through the direct transfer of acid-base equivalents between the animal and its external environment. Compensation is achieved by adjusting plasma HCO₃⁻ levels in the blood through the differential regulation of H⁺ and HCO₃⁻ effluxes which are coupled to the influx of Na⁺ and Cl⁻. As a result, these compensatory changes can negatively impact respiration and osmoregulation. When there is decreased availability of oxygen in water, due for example to increase temperature, fish maximize the efficiency of O₂ uptake by regulating heart rhythm, blood pressure, and blood flow through the gills. Fish also rely on pH alterations of their blood to maximize hemoglobin uptake and delivery of oxygen and utilize the combined Bohr and Root effects to realize blood oxygen concentrations 25-30 times higher than what is available in the environment. The combined effects of ocean acidification ...