Modelling the relationship between zooplankton biomass and environmental variations in the distribution of210Po during a one year cycle in northwestern Mediterranean coastal waters.
To clarify the relationship between zooplankton biomass and the environmental kinetics of the natural radionuclide210Po during a one-year period (October 1995 to November 1996) in northwestern Mediterranean coastal waters, a modelling analysis was applied. Using210Po concentrations in seawater and zooplankton, the210Po uptake rate constant from food for zooplankton was evaluated using a biokinetics calculation involving the uptake and the excretion rate constants between seawater and zooplankton. Using the transfer constants obtained, the210Po concentrations in zooplankton were reconstructed and validated by observed concentrations. The simulation results were in good agreement with the measured210Po concentrations in zooplankton. Assuming that210Po fecal excretion represents the majority of the excretion of210Po from zooplankton, the fecal matter associated210Po vertical flux was calculated, and compared with the observed vertical fluxes of210Po measured in sediment traps. The modelling evaluation showed that fecal pellet vertical transport could not fully explain the observed sinking fluxes of particulate organic matter at 150 m depth, suggesting that other sinking biodetrital aggregates are also important components of the plankton-derived vertical flux of210Po. The relationship between210Po concentration in seawater and that in rain and dry fallout and their potential effect on210Po concentrations in zooplankton at this location were also examined. A similar, but diphased trend between210Po in zooplankton and210Po in rain and dry fallout deposition rate was demonstrated.210Po concentrations in the dissolved phase of seawater tended to diminish as mean daily rainfall increased suggesting that rain inputs serve as a210Po dilution mechanism in seawater at this location.
Departmento de Ecología, CICESE, Carr. Tijuana, Ensenada 3918, Zona Playitas, 22890, Ensenada, B. C., Mexico. Electronic address: jfarber@cicese.mx.
Jaime
J
Färber Lorda
Biology Department, Abiko Laboratory, Central Research Institute of Electric Power Industry, Abiko, Japan.
Yutaka
Y
Tateda
Institute Bobby, 8 Allée des Orangers, 06320 Cap d'Ail, France.
Scott W
SW
Fowler
D000818:Animals; D018533:Biomass; D008956:Models, Chemical; D052638:Particulate Matter / Q000032:analysis; D011059:Polonium / Q000032:analysis*; D011834:Radiation Monitoring; D012623:Seawater / Q000737:chemistry; D014875:Water Pollutants, Radioactive / Q000032:analysis*; D015048:Zooplankton / Q000254:growth & development*
D052638:Particulate Matter; D014875:Water Pollutants, Radioactive; D011059:Polonium
210-Polonium; Biokinetics; Model; One year cycle; Rainfall; Zooplankton