The varying radiocarbon activity of some recent submerged Estonian plants grown in the early 1990s.

Abstract

Eleven samples of aquatic plants from three Estonian lakes were analyzed for their radiocarbon content in a collaboration between the laboratories in Tallinn and Uppsala. delta (super 13) C values for the actual species were compiled to allow normalization of activities measured in Tallinn without delta (super 13) C values. The range for well determined species is usually a few per mil and the statistical uncertainty > or =1 per mil delta (super 13) C values vary considerably for different Potamogeton species and Myriophyllum spp. Lake Antu Sinijarv and Lake Paidre are hard-water lakes containing 300 and 200 mg HCO (sub 3) -/L, respectively. One sample consisted of a carbonate crust deposited on a Ceratophyllum demersum plant in L. Antu Sinijarv. Its delta (super 14) C value was -147.3+ or -6.7 per mil in 1990, whereas the plant had a value of -74.1+ or -8.0 per mil (delta (super 13) C = -35.0 per mil). The same species in L. Paidre had a delta (super 14) C value of +8.0+ or -8.8 per mil (delta (super 13) C = -25.2 per mil) in 1992. Other species in L. Paidre contained more (super 14) C, from a delta (super 14) C value of about +30 per mil to about +155 per mil, the latter value measured in Tallinn on floating leaves of Nuphar lutea, close to that of the contemporaneous atmospheric CO (sub 2) . In the third lake, Lake Punso, containing >30 mg HCO (sub 3) -/L, the stems of Nuphar lutea exhibited in 1990 a memory effect: the activity, delta (super 14) C = 209.6+ or -10.3 per mil, significantly exceeded that of the contemporaneous atmospheric CO (sub 2) . However, the floating leaves of the same plant had the delta (super 14) C value 143.1+ or -10.0 per mil, close to the atmospheric (super 14) C level in 1990. The memory is explained by nutrients stored in the root stock, used when the growth starts.