Trace elements in bivalve shells from the Río Cruces, Chile

Abstract

In May 1960, the largest recorded earthquake in the earth's history struck southern Chile, and lowered the course of the Río Cruces by approximately 2 m. This created a wetland, which was colonised by the waterweed Egeria densa and, subsequently, by large populations of the blacknecked swan, which fed on the weed. Reported catastrophic declines in the weed and swan populations in 2004 coincided with the opening of a large cellulose plant upstream, leading to popular and scientific condemnation of the plant. In 2008, samples of the freshwater bivalve Diplodon chilensis were retrieved from the bed of the Río Cruces at several locations downstream of the plant, and the growth patterns of the bivalves were studied in thin section. Trace element profiles of bivalves were determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP/MS). Some of the bivalves had ages of almost 50 yr, indicating that they colonised the drowned riverbed less than a decade after the earthquake. There were no growth recessions or abnormalities in the shells corresponding to 2004, the year the plant opened. Patterns of trace elements in the shells describe aspects of the evolution of the watershed, track annual cycles in rainfall and indicate patterns of soil erosion and/or sediment input. Sr, Ba and Mn have strong annual cyclicity; Ba and Mn are viewed as indicators of soil erosion. Peaks in Ba were large immediately after the earthquake, whereas Ba peaks in the last few decades were of much smaller amplitude. The changes in Ba patterns probably indicate changes in patterns of soil erosion: high erosion rates immediately after the earthquake, slowing as the basin fills. Cu appears as annual low-level peaks in abundance in about 1975, which continue to the present. This may be the result of spraying of fungicides in the watershed, which is heavily used by agriculture. Similarly

Paleoenvironmental reconstruction using stable isotopes and trace elements from archaeological freshwater bivalve shell fragments in Northwest Patagonia, Argentina

“…δ 13 C shell and Sr/Ca ratio are also correlated (P = 0.0154, R = 0.83) only if data from layers 5 and 7 are excluded. These correlations are consistent with the results reported by Risk et al (2010), who have found similar peaks of δ 18 O and Sr/Ca and Ba/Ca ratios in the same species in Chile in summer growth lines, considering that summer is the dry season in both Chilean an Argentine Patagonia. In our study, the Mn/Ca ratio was not considered for the analysis because it does not show any significant trend along the sequence and is not correlated with the other proxies.…”

“…High Mn/Ca ratio has been reported as an indication of high aquatic primary productivity Carroll and Romanek 2008). Particularly for D. chilensis, which shows maximum growth rate in winter (Soldati et al 2009;Rocchetta et al 2014), Risk et al (2010) have detected Mn peaks in winter growth lines interpreting that increased precipitations and river discharge can augment erosion, liberating soluble Mn. According to Lee and Wilson (1969), Sr/Ca ratio is expected to show positive correlation with reduced river discharge and/or with increased evaporation.…”

Trace elements in mussel shells from the Brazos River, Texas: environmental and biological control

“…While the low water manganese concentrations (0.1-0.6 ppb) are consistent with Keeney-Kennicutt and Presley's (1986) measurements (0.1-2.3 ppb), we will not draw conclusions based on the water Mn data because our water samples were not filtered and acidified immediately upon collection. Turekian and Scott (1967) attribute the suspended particulate manganese concentration in the Brazos River (690 ppm) to soil erosion, as found in other river Mn studies (e.g., Shiller, 2002;Risk et al, 2010). The highest water Mn concentration values in our study were from samples taken during times of high flow.…”

Trace element composition of freshwater pearl mussels Margaritifera spp. across Eurasia: Testing the effect of species and geographic location

“…The role of river bed sediments and river suspended matter should also be kept in mind. For example, a close correlation in the Mn content of bivalve shells and river discharge was reported to originate from the erosion and downstream transport of Mn-bearing sediments (Risk et al, 2010). In the river water systems of this study, however, the effect of a Mn-rich silicate riverine suspended matrix should be limited because the centered PCA patterns of the data set identify Mn as an important component for both biochemical and geographical factors ( Fig.…”