Evaluation of the role of submerged plant beds in the metal budget of a fluvial lake

Abstract

In a study of a large fluvial lake (Lake St . Pierre, St. Lawrence River system, Quebec), we have determined the biomass of the submerged vegetation (dominated by Vallisneria americana and Potamogeton spp) during the peak seasonal biomass (August) and senescence (October), and have estimated the content of Cd, Cr, Cu, Ni, Pb and Zn in the above-ground portions of these plants . Multispectral remote sensing data (MEIS-II) were used to extrapolate from point measures of biomass (g m_2) to the entire area of the lake (Lavoie et al., 1991). By combining field information (biomass values and metal concentrations) with the more extensive remote sensing data base of biomass values, and by using geostatistical estimation techniques (kriging), we have estimated the seasonal storage of metals in Lake St . Pierre plants to be : 30 kg Cd, 89 kg Cr, 450 kg Cu, 280 kg Ni, 71 kg Pb and 2200 kg Zn . During the seasonal biomass peak, the quantities of Cd, Pb and Zn stored in the plants were higher than those dissolved in the water column, but much lower than those present in the surficial, recent sediments . Mass balance calculations for the summer months indicated that the 'macrophyte' compartment represented only a small proportion of the metals entering the lake : Cu and Ni, <1% ; Cd and Zn, 2% ; Pb, 4% . Senescence and the downstream drifting of plant material noted in October suggested that most of the metals associated with the above-ground parts of the submerged vegetation were not recycled within the lake, but instead were exported at the end of the summer .

Trace metals in submerged plants of the St. Lawrence River

“…Our data from Lake St. Pierre suggest that this approach may be unwise. In this lake, P. richardsonii has a much higher specific biomass than V. americana (St-Cyr et al 1994) and consistently exhibits lower tissue metal concentrations (except for Pb). At all seven sampling stations where P. richardsonii was collected.…”

Metals (Fe, Mn, Zn) in the root plaque of submerged aquatic plants collected in situ: Relations with metal concentrations in the adjacent sediments and in the root tissue

“…V. americana has a fibrous root system extending to a maximum of about 10 cm into the sediment, depending on the substrate type. The number of rosettes per unit surface area was estimated from the biomass of V.umericunu, according to the regression equation relating these two measures for Lake St. Pierre (St-Cyr et al 1994). From the mean root biomass per rosette (station #48: 0.014 g dry weight; station #50: 0.019 gdw) and the mean of DCB-extracted Fe on roots (station #48: 135 pg of Fe/g root dry weight; station #50: 88 pg of Fe/g rdw), amounts of 0.25 g of Fe per square meter of lake bottom at station 48 and 0.52 g of Fe/m2 at station 50 were calculated for the root coatings.…”

Oxidative effects, nutrients and metabolic changes in aquatic macrophyte, Elodea nuttallii, following exposure to lanthanum

“…It has also been shown that aquatic macrophytes can uptake metals directly from water and accumulate them in their shoots because they are completely submerged and have a very thin cuticle (St-Cyr et al, 1994;Wang et al, 2010b. E. nuttallii, a submerged plant native to North America, is known for its fast growth rate and is easily cultured in the laboratory.…”