Depositional fluxes of metals and phytoplankton in Windermere as measured by sediment traps1

Abstract

Monthly sediment trap samples collected from a deep water station (42 m) in Windermere for a period of 1 year were analyzed for 0.5 M HCl extractable and total Fe, Mn, Al, Pb, Cu, Zn, total C, N, and total solids. Concomitant algal counts showed the year to be fairly typical in terms of the known sequence of phytoplankton.The annual depositional fluxes are compared with previously determined values based on sediment studies. The ratio of the annual trap to sediment flux for Al (5 1) indicates the absence of local sediment resuspension. The ratios for Fe, Pb, and Zn (1.1, 1.4, and 1.5, but not significantly > 1) suggest some possible biogeochemical cycling at the sediment-water interface. The deposition of Fe, Al, and Pb is predominantly associated with detrital material and occurs mainly during winter. The behavior of Zn is largely independent of other variables examined. The ratios for C (1.8), total solids (2.2), N (3.2), Mn (8.6), and Cu (9.5) are all significantly > 1. The C and N values are thought to reflect the microbial breakdown of organic matter at the sediment surface and more particularly the preferential degradation of proteinaceous (i.e. N rich) material. The major influence on the deposition and recycling of Mn is its well known redox cycle involving oxidative precipitation and reductive remobilization.Cu undergoes an independent deposition-remobilization cycle, probably related to uptake by diatoms and their rapid microbial decomposition after sedimentation.

Mercury dynamics in lake sediments

“…The average (±SD) {C org }:{N} molar ratios of the sediments, over the whole cores, were 16.7 ± 0.7, 16.6 ± 2.2, 16.3 ± 2.3 and 13.7 ± 1.2 for Basins A and B of Lake Tantaré and for Lakes Bédard and Holland, respectively. Such large {C org }:{N} ratios are consistent with organic matter being mainly humic substances derived from the watershed rather than autochtonous organic matter (Feyte et al, 2010); indeed, these ratios are much larger than those (6.4-6.6) reported for phytoplankton or for settling particles in a productive lake (Redfield, 1934;Hamilton-Taylor et al, 1984), but close to those of soil humic substances (Buffle, 1988). The {C org }:{N} ratio in the top 0.5-cm sediment layer of Basin A was 15.5, a value very close to that measured (15.3 ± 3.4) in the Fe-rich diagenetic material collected on Teflon sheets (Table 3).…”

Vertical transport of heavy metals by settling particles in Lake Zurich

“…The latter may in turn act as solid substrate for other elements such as Pb and Cr. A similar study by Hamilton-Taylor et al (1984) on the deposition of Fe, Mn, Pb, Cu, Al, Zn, C, and N in sediment traps in Windermere showed the importance of a diatom bloom on the scavenging of Cu; the role of allochthonous material was more important in that case than in Lake Zurich.…”

Carbon and nitrogen loss rates during aging of lake sediment: Changes over 27 years studied in varved lake sediment

“…These experiments, which typically have been conducted over a period of weeks up to a year, have reported high decay rates and a large variability, spanning over three orders of magnitude; the reason for this is assumed to be differing algal material, incubation temperatures, and the use of single-versus double-exponential decay models (Lehman et al 2002). Besides laboratory experiments, there have been a number of studies in lakes with oxic hypolimnion, where sediment trap accumulation rates were compared to sediment core accumulation rates, i.e., sediment traps were emptied weekly, biweekly, or at slightly longer intervals, and the cumulative sedimentation rates from the traps were compared to the net annual or seasonal accumulation rates found in sediment cores (Hamilton-Taylor and Willis 1984;Jonsson and Jansson 1997;Teranes and Bernasconi 2000). These studies reported loss rates for C of 25-45% and for N of 40-70% after 1-3 yr. Lehmann et al (2002) did a similar study in seasonally anoxic Lake Lugano, and the net loss of C was 15-20%.…”