Limnological investigation of biogenic silica sedimentation and silica biogeochemistry in Lake St. Moritz and Lake Zürich

Quantifying human-induced eutrophication in Swiss mountain lakes since AD 1800 using diatoms

“…For comparison, independent geochemical proxies (C org and BSi) are displayed, ie, for Lej da San Murezzan C org (own data, same core as diatoms) and BSi (redrawn from Schelske et al, 1987, parallel core), for Lej da Silvaplauna BSi (redrawn from Blass et al, 2007a, parallel core) and for Lej da la Tscheppa C org (own data, same core as diatoms) increased concentration of biogenic silica (BSi) and organic carbon (C org ). The BSi concentrations in the sediments of Lej da San Murezzan increased distinctly between AD 1910 and 1930, representing a four-fold increase of silica deposition with peak concentrations in the 1960s and 1980s (Figure 8, data redrawn from Schelske et al, 1987). Similarly, also the C org record reflects nutrient changes; and high diatom-inferred nutrient levels are in general associated with elevated C org values, even though the magnitude of nutrient enrichment seems hardly reflected in the C org record (Figure 8).…”

“…has a maximum depth of 44 m, an area of 0.8 km 2 and a water residence time of <1 yr (Züllig, 1982a;Schelske et al, 1987). The lake is ice-covered from January to May (ice-break up dates have been recorded since AD 1832; Livingstone, 1997), followed by a stable summer stratification from June through November (Bosli-Pavoni, 1971) causing hypolimnetic anoxia.…”

“…By analysing the fossil pigment record, the eutrophication history of Lej da San Murezzan was assessed qualitatively (Züllig, 1982a, b). Increased nutrient concentrations stimulating primary production also altered the silica biogeochemistry (Schelske et al, 1987) and the amount of total organic carbon (TOC) and sulphur (Ariztegui and Dobson, 1996). Moreover, traces of human activity were recorded in Lej da Silvaplauna, altering the silica concentration (Blass et al, 2007a) even though the visible effects of human activity in the sediment seem less pronounced than in Lej da San Murezzan.…”

Silicon Retention in River Basins: Far-reaching Effects on Biogeochemistry and Aquatic Food Webs in Coastal Marine Environments

“…Primary production in rivers is often light-limited due to high turbidity and, furthermore, the retention of DSi is limited to available deposition sites. Natural deposition sites are, of course, lakes where eutrophication has definitely increased diatom production and enhanced the retention of DSi (39,40). One of the best known cases of this phenomenon is the Great Lakes (41).…”

Compound-specific carbon and nitrogen isotopic compositions of chlorophyll a and its derivatives reveal the eutrophication history of Lake Zurich (Switzerland)

“…(but also myxoxanthophyll, canthaxanthin and echinenone) vs. fucoxanthin (Züllig, 1982;. The fucoxanthin peak in 1896 followed by its progressive decrease (Züllig, 1982; agrees with the decreasing silica accumulation rates in the sediment (Schelske et al, 1987), indicating that diatom populations have decreased since then, whereas cyanobacteria (and especially P. rubescens) have become predominant in the lake (Bossard et al, 2001;Posch et al, 2012).…”