Dataset Information

Tracking Baltic hypoxia and cod migration over millennia with natural tags.

ABSTRACT: Growing hypoxic and anoxic areas in coastal environments reduce fish habitat, but the interactions and impact on fish in these areas are poorly understood. Using "natural tag" properties of otoliths, we found significant correlations between the extent of Baltic Sea hypoxia and Mn/Ca ratios in regions of cod (Gadus morhua) otoliths corresponding to year 1 of life; this is associated with elevated bottom water dissolved manganese that increases with hypoxia. Elevated Mn/Ca ratios were also found in other years of life but with less frequency. We propose that cod exhibiting enhanced Mn/Ca ratios were exposed to dissolved manganese from hypoxia-induced redox dynamics in nursery areas. Neolithic (4500 B.P.) cod otoliths (n = 12) had low levels of Mn/Ca ratios, consistent with low hypoxia, but a single otolith dated to the younger Iron Age had a distinct growth band with an elevated Mn/Ca ratio. Sr/Ca patterns reflecting changes in environmental salinity and temperature were similar in both modern and Stone Age otoliths, indicating consistent migration habits across time, and Ba/Sr ratios in modern cod otoliths indicate increasing use of a more saline habitat with age. Using elemental ratios, numerous existing archival collections of otoliths could provide the means to reconstruct hypoxia exposure histories and major patterns of fish movement near "dead zones" globally.

SUBMITTER: Limburg KE

PROVIDER: S-EPMC3107296 | biostudies-other | 2011 May

REPOSITORIES: biostudies-other

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Tracking Baltic hypoxia and cod migration over millennia with natural tags.

Limburg Karin E KE Olson Carina C Walther Yvonne Y Dale Darren D Slomp Caroline P CP Høie Hans H

Proceedings of the National Academy of Sciences of the United States of America 20110425 22

Growing hypoxic and anoxic areas in coastal environments reduce fish habitat, but the interactions and impact on fish in these areas are poorly understood. Using "natural tag" properties of otoliths, we found significant correlations between the extent of Baltic Sea hypoxia and Mn/Ca ratios in regions of cod (Gadus morhua) otoliths corresponding to year 1 of life; this is associated with elevated bottom water dissolved manganese that increases with hypoxia. Elevated Mn/Ca ratios were also found ...[more]

PMID: 21518871

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Project description: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.

Dataset Information

Tracking Baltic hypoxia and cod migration over millennia with natural tags.

Publications

Tracking Baltic hypoxia and cod migration over millennia with natural tags.

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