Severe thiamine deficiency in eastern Baltic cod (Gadus morhua)

The eastern Baltic cod (Gadus morhua) population has been decreasing in the Baltic Sea for at least 30 years. Condition indices of the Baltic cod have decreased, and previous studies have suggested that this might be due to overfishing, predation, lower dissolved oxygen or changes in salinity. Howev...

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Bibliographic Details
Published in:	PloS one Vol. 15; no. 1; p. e0227201
Main Authors:	Engelhardt, Josefin, Frisell, Oscar, Gustavsson, Hanna, Hansson, Tomas, Sjöberg, Rajlie, Collier, Tracy K, Balk, Lennart
Format:	Journal Article
Language:	English
Published:	United States Public Library of Science 02-01-2020 Public Library of Science (PLoS)
Subjects:	Analysis Analytical chemistry Animal reproduction Animals Apoenzymes Biological markers Biology and Life Sciences Biomarkers Brain Brain - metabolism Chemical analysis Chromatography Condition factor Dehydrogenases Dissolved oxygen Earth sciences Eggs Environmental science Enzymes Fatty acids Female Fish and Aquacultural Science Fish Diseases - metabolism Fishes Fisk- och akvakulturforskning Gadus morhua Gadus morhua - metabolism High performance liquid chromatography Homeostasis Invertebrates Liquid chromatography Liver Liver - metabolism Male Medicine and Health Sciences Metabolism Metabolites Organic chemistry Otoliths Overfishing Oxygen Physical Sciences Population Population decline Predation Predation (Biology) Pyrimidines Research and Analysis Methods Salinity Salmon Spawning Thiamine Thiamine - analysis Thiamine - metabolism Thiamine Deficiency - metabolism Thiamine Deficiency - veterinary Thiamine diphosphate Tissue analysis Transketolase Trout Vertebrates Vitamin B Vitamin deficiency Weight Baltic Sea Germany Newfoundland and Labrador Sweden
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Summary:	The eastern Baltic cod (Gadus morhua) population has been decreasing in the Baltic Sea for at least 30 years. Condition indices of the Baltic cod have decreased, and previous studies have suggested that this might be due to overfishing, predation, lower dissolved oxygen or changes in salinity. However, numerous studies from the Baltic Sea have demonstrated an ongoing thiamine deficiency in several animal classes, both invertebrates and vertebrates. The thiamine status of the eastern Baltic cod was investigated to determine if thiamine deficiency might be a factor in ongoing population declines. Thiamine concentrations were determined by chemical analyses of thiamine, thiamine monophosphate and thiamine diphosphate (combined SumT) in the liver using high performance liquid chromatography. Biochemical analyses measured the activity of the thiamine diphosphate-dependent enzyme transketolase to determine the proportion of apoenzymes in both liver and brain tissue. These biochemical analyses showed that 77% of the cod were thiamine deficient in the liver, of which 13% had a severe thiamine deficiency (i.e. 25% transketolase enzymes lacked thiamine diphosphate). The brain tissue of 77% of the cod showed thiamine deficiency, of which 64% showed severe thiamine deficiency. The thiamine deficiency biomarkers were investigated to find correlations to different biological parameters, such as length, weight, otolith weight, age (annuli counting) and different organ weights. The results suggested that thiamine deficiency increased with age. The SumT concentration ranged between 2.4-24 nmol/g in the liver, where the specimens with heavier otoliths had lower values of SumT (P = 0.0031). Of the cod sampled, only 2% of the specimens had a Fulton's condition factor indicating a healthy specimen, and 49% had a condition factor below 0.8, indicating poor health status. These results, showing a severe thiamine deficiency in eastern Baltic cod from the only known area where spawning presently occurs for this species, are of grave concern.
Bibliography:	Competing Interests: The authors have declared that no competing interests exist.
ISSN:	1932-6203 1932-6203
DOI:	10.1371/journal.pone.0227201