Deficiency syndromes in top predators associated with large-scale changes in the Baltic Sea ecosystem.

• Published in: PLOS ONE
• Main Authors: Sanna Majaneva, Emil Fridolfsson, Michele Casini, Catherine Legrand, Elin Lindehoff, Piotr Margonski, Markus Majaneva, Jonas Nilsson, Gunta Rubene, Norbert Wasmund, Samuel Hylander
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2020
• Subjects: Medicine; R; Science; Q; Salmo salar
• Online Access: https://doi.org/10.1371/journal.pone.0227714; https://doaj.org/article/5e4103a1484f4de7878d325275401bca

Vitamin B1 (thiamin) deficiency is an issue periodically affecting a wide range of taxa worldwide. In aquatic pelagic systems, thiamin is mainly produced by bacteria and phytoplankton and is transferred to fish and birds via zooplankton, but there is no general consensus on when or why this transfer is disrupted. We focus on the occurrence in salmon (Salmo salar) of a thiamin deficiency syndrome (M74), the incidence of which is highly correlated among populations derived from different spawning rivers. Here, we show that M74 in salmon is associated with certain large-scale abiotic changes in the main common feeding area of salmon in the southern Baltic Sea. Years with high M74 incidence were characterized by stagnant periods with relatively low salinity and phosphate and silicate concentrations but high total nitrogen. Consequently, there were major changes in phytoplankton and zooplankton, with, e.g., increased abundances of Cryptophyceae, Dinophyceae, Diatomophyceae and Euglenophyceae and Acartia spp. during high M74 incidence years. The prey fish communities also had increased stocks of both herring and sprat in these years. Overall, this suggests important changes in the entire food web structure and nutritional pathways in the common feeding period during high M74 incidence years. Previous research has emphasized the importance of the abundance of planktivorous fish for the occurrence of M74. By using this 27-year time series, we expand this analysis to the entire ecosystem and discuss potential mechanisms inducing thiamin deficiency in salmon.