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

Abstract

Vitamin B 1 (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.

Genetic basis of thiaminase I activity in a vertebrate, zebrafish Danio rerio

“…Populations of fish and wildlife have experienced declines in numbers and, in certain cases, complete reproductive failures over large geographic areas from thiamine deficiency. Collapse of lake trout ( Salvelinus namaycush ) populations in the Great Lakes of North America 3 , loss of Atlantic salmon ( Salmo salar ) spawning runs in Baltic Sea tributaries in Sweden and Finland 4 , and widespread declines in Northern European bird populations 5 , 6 have all been linked to thiamine deficiency. Most recently, populations of Chinook salmon ( Oncorhynchus tshawytscha ) from the Central Valley of California, North America have symptoms of thiamine deficiency 7 .…”

“…Indeed, these observations have led to the recognition of thiamine deficiency as an emerging issue affecting global biodiversity 8 .Thiamine is a required co-factor for enzymes in essential metabolic pathways, including energy metabolism and amino acid synthesis. Thiamine deficiency syndromes have been observed in livestock and captive animals that are fed a homogenous diet and in wildlife under conditions of human-influenced ecological changes 4,6,7 . Thiamine synthesis, degradation, and salvage pathways are found in some bacteria, unicellular animals, and plants.…”

Ontogenetic Dietary Changes and Thiamine Status of Lake Ontario Chinook Salmon, 2005–2006

“…Beginning in the early 1990s, thiamine deficiency in fish was considered a sign of a disrupted ecosystem (Majaneva et al 2020). The major producers of thiamine in aquatic ecosystems are phytoplankton and bacteria (Croft et al 2006).…”

A multi‐biomarker study on Atlantic salmon (Salmo salar L.) affected by the emerging Red Skin Disease in the Baltic Sea

“…As severe maternally transferred thiamine deficiencies were the major cause for the M74 syndrome-a reproductive disorder in yolk-sac fry of Atlantic salmon, which deeply affected salmon populations within the Baltic Sea-and widespread thiamine deficiencies in the Northern Hemisphere have been suggested (Balk et al, 2016;Bengtsson et al, 1999;Harder et al, 2018;Majaneva et al, 2020), the thiamine contents in liver samples were analysed. The free form of thiamine and the physiologically most important metabolite thiamine pyrophosphate were included in the RDA for liver-associated parameters and results suggested a negative correlation between the free form and the disease.…”