Bottom-up control of mesozooplankton thiamine levels in the Baltic Sea
(English)Manuscript (preprint) (Other academic)
Thiamine (vitamin B1) is an essential vitamin for many organisms, including all animals. In aquatic systems it is synthesised by prokaryotes and photoautotrophs and transferred to higher trophic levels through predation. This study quantifies for the first time the in situ thiamine concentrations of plankton communities in the brackish Baltic Sea area and analyses which environmental and biotic factors regulate these concentrations. Samples from 93 off-shore stations covering different seasons and two years (2004 and 2005) were included in the analyses. The thiamine concentrations in the phyto- and mesozooplankton varied with season and community composition. Phytoplankton thiamine concentrations were highest in August, which was most likely due to high abundances of thiamine-rich cyanobacteria, and those in the zooplankton were highest in November. The thiamine concentrations in the zooplankton were positively correlated to those in the phytoplankton, which suggests a bottom-up effect for the thiamine status of the zooplankton and possibly also for that of higher trophic levels. A positive correlation between the concentrations of thiamine and the antioxidant zooplankton pigment astaxanthin may indicate an aetiology of thiamine deficiency involving oxidative stress. In both plankton fractions the concentrations of the active vitamin, thiamine diphosphate (TDP), were negatively correlated to phytoplankton C:P ratios, suggesting a coupling between low TDP concentrations and cellular P-limitation in the phytoplankton. Significantly lower TDP concentrations were observed in the phyto- and zooplankton communities in 2005 than in 2004. P-limitation in the phytoplankton cells in 2005 was not related to low availability of dissolved inorganic P in the water. Our results suggest that a low intracellular P-availiability hinders the phosphorylation of thiamine to TDP inside the phytoplankton cells despite the availability of enough P in the water and enough free thiamine in the cells. Further studies are needed to explain the mechanism behind these field observations.
Research subject Marine Ecology
IdentifiersURN: urn:nbn:se:su:diva-89151OAI: oai:DiVA.org:su-89151DiVA: diva2:616045