A framework for 210Pb model selection and its application to 37 cores from Eastern Canada to identify the dynamics and drivers of lake sedimentation rates

Abstract

Lake sedimentation rate represents a synthetic metric of ecosystem functioning. Many localized studies have reported a significant association between land use/land cover changes and lake sediment mass accumulation rates, with a few global syntheses echoing these findings at larger scales. In the literature, studies evaluating lead-210 ( 210 Pb) for establishing sediment chronologies will report at least one of three dating models, but the constant rate of supply (CRS) model is the most widely used. However, it is often unclear how or why this model is selected, despite its influence on the interpretation of many subsequent analyses about ecosystem dynamics and functioning. It would thus be advantageous to design an objective and semi-automated way of

Zooplankton assemblage structure and diversity since pre‐industrial times in relation to land use

“…However, this pattern seemingly did not translate into many significant functional diversity changes (Figure 4), and lakes of greater functional diversity showed less movement in the PCA through time in relation to land use (Figure 5b). It should be noted that recent increases in global sedimentation rates along with sediment compaction can influence mass accumulation rates of lake sediments (Baud et al, 2021, 2022), and so our temporal local diversity declines could be partially related to more years being integrated in the bottom versus top samples. In our analysis from a subset of 27 dated full cores, we found that the top 1 cm represented on average 11 ± 9 years of deposition, whereas an average of 18 ± 11 years were integrated in the bottom 1‐cm interval (for the full cores the bottom was the lowest 1‐cm sample that could be dated using 210 Pb activities).…”

“…Additionally, full cores were collected in a subset of 27 lakes (Supporting Information Figure S2) to analyse 210 Pb activity profiles with a gamma well detector. These profiles were used to estimate sediment mass accumulation rates and potential changes in temporal resolution between top and bottom samples (Baud et al, 2022). Further details on sediment dating and sedimentation rate estimations are provided in Griffiths et al (2021) and Baud et al (2022).…”

“…These profiles were used to estimate sediment mass accumulation rates and potential changes in temporal resolution between top and bottom samples (Baud et al, 2022). Further details on sediment dating and sedimentation rate estimations are provided in Griffiths et al (2021) and Baud et al (2022).…”

“…Subfossil cladoceran assemblages may also provide a more integrative, whole‐lake portrait than discrete pelagic samples of contemporary communities because the sediments deposited in the deepest part of a lake contain particles focused potentially from the entire lake basin, including the littoral zone (García‐Girón et al, 2018; Jeppesen et al, 2011). Likewise, a sediment layer 1 cm in thickness often integrates multiple years of deposition (Baud et al, 2022).…”

Congruence of water column, contemporary and pre‐industrial sediment cladoceran assemblages in 85 Canadian lakes of contrasting human impact levels

“…Consequently, when considering pelagic taxa only, it was also hypothesised (2) that water column-contemporary sediment similarity would increase as water column samples should be dominated by pelagic taxa in most lakes. When analysing environmental drivers of species composition, we hypothesised that (3) contemporary sediment samples would be most strongly structured by environmental variables since they generally integrate seasons, multiple years of deposition, and species from the entire lake basin (Baud et al, 2022;Jeppesen et al, 2011). Preindustrial samples were instead expected to be structured by morphometric variables that should be mostly stable over time.…”