90Sr in Zostera marina from the Gulf of Gdansk (southern Baltic Sea)

Sr-90 activity was determined in Zostera marina collected in the Gulf of Gdansk in 2008-2013. Sr-90 activity in Z. marina from Jama Kuznicka and Klif Orlowski range from 0.83 Bq kg(-1) d. w. to 3.78 Bq kg(-1) d. w. and from 0.68 Bq kg(-1) d. w. to 4.95 Bq kg(-1) d. w., respectively. The plants collected in spring-summer showed significant differences between Sr-90 content in blades -1.55 Bq kg(-1) d. w. in 2011 and 2.18 Bq kg(-1) d. w. in 2013, and in roots -7.75 Bq kg(-1) d. w. and 11.44 Bq kg(-1) d. w., respectively. The reduction in Sr-90 concentrations in Z. marina roots to 1-2 Bq kg(-1) d. w. in summer resulted from the transport of this element to the young parts of the plant. In autumn and winter, the Sr-90 content in the blades of Z. marina was increasing and reached the maximum of 3.77 Bq kg(-1) d. w. This could be explained by the process opposite to dilution, related to the biomass reduction and strontium concentration in the plant tissues. Changes in Sr-90 concentration in Z. marina tissues are affected by isotope concentration in seawater as well as by salinity, which affects the concentration of Ca2+-for which Sr2+ is a chemical analogue.