STRESS RESPONSES AND METAL EXCHANGE KINETICS FOLLOWING TRANSPLANT OF THE AQUATIC MOSS FONTINALIS-ANTIPYRETICA

1. We studied stress responses and metal exchange (uptake and loss) ki netics in the aquatic moss Fontinalis antipyretica Hedw. following tra nsplant (in plastic mesh bags) to clean and metal-contaminated river s ites and under laboratory conditions. 2. The stress response (estimate d on the basis of chlorophyll:phaeophytin ratio) was more pronounced, and the moss took longer to recover, following transplant to heavily c ontaminated sites. 3. Metal uptake over the 28 day exposure period was predicted well by a two-compartment kinetic model: uptake velocity wa s initially high and gradually declined, with metal concentration in t he moss showing a tendency to reach an equilibrium with metal concentr ation in the water. Mean uptake rate, time to reach equilibrium and me tal concentration in moss at equilibrium all increased with increasing metal concentration in the water. 4. Bioconcentration constants calcu lated on the basis of our data rank the metals studied in the order Zn < Ni < Co < Cu < Pb < Cd. 5. Following retransplant of mosses to a cl ean site, metal loss was not predicted well by a passive exchange mode of the above type; instead, two phases (rapid and slow) were apparent . Loss rates during both phases, and proportion of metal load lost dur ing the rapid phase, were proportional to the concentration of metal i n the moss at the start of the recuperation trial. 6. We present nomog rams to allow estimation of severity of contamination on the basis of metal concentration in moss and duration of transplant.