Reconstructing consequences of lifetime hypoxia exposure on metabolism of demersal fish in the northern Gulf of Mexico using otolith chemistry

• Published in: Environmental biology of fishes 2023-11, Vol.106 (11), p.2045-2057
• Main Authors: Valenza, Apria N., Altenritter, Matthew E., Walther, Benjamin D.
• Format: Article
• Language: English
• Subjects: Age; Animal Systematics/Taxonomy/Biogeography; Anthropogenic factors; Biomedical and Life Sciences; Calcium; Chemical analysis; Demersal fish; Ecological function; Ecophysiology; Environment; Environmental impact; Environmental stress; Exposure; Fish; Fractions; Freshwater & Marine Ecology; Growth rate; Human influences; Hypoxia; Juveniles; Lethal effects; Life history; Life Sciences; Life span; Magnesium; Manganese; Metabolic response; Metabolism; Nature Conservation; Nutrient loading; Pelagic fisheries; Runoff; Zoology
• ISSN: 0378-1909; 1573-5133
• DOI: 10.1007/s10641-023-01483-1

Hypoxia is a worldwide natural phenomenon that is becoming increasingly more severe in the northern Gulf of Mexico (nGoMex) where it is driven by anthropogenic nutrient loading in riverine runoff. In addition to outright mortality, hypoxia can have a range of ecophysiological effects on demersal and pelagic organisms, from altering species niche widths to stifling growth rates. While hypoxia exposure is known to have many sub-lethal effects for early life history stages of demersal fishes, quantifying exposure histories and consequences for the entire lifespan of exposed individuals is critical for understanding how hypoxia impacts ecosystem functions. Lifetime hypoxia exposure patterns and potential consequences to metabolism were reconstructed using otolith chemical analyses (Mn:Ca, Mg:Ca and Mn:Mg values) in Atlantic Croaker ( Micropogonias undulatus ) collected in the northern Gulf of Mexico. Age-0 croaker were found to have the highest Mn:Ca duration fractions, indicating that a large proportion of juveniles are exposed to hypoxia within the first year of life. However, otolith chemical proxies of metabolism (Mg:Ca) did not differ by hypoxia exposure groups until Age-1 and Age-2. These patterns were unexpected and contrary to those found for comparable assessments of putative metabolic response to hypoxia in other systems, potentially due to the relative hypoxia tolerance of Atlantic Croaker that may allow increased foraging rates in low oxygen waters. Understanding the complex interactions between hypoxia and the lifetime growth and metabolism in mobile fishes is necessary to make robust predictions about the ecosystem consequences of this pervasive and growing environmental stressor in the Gulf of Mexico.