Postglacial hydroclimate in the southern interior of British Columbia (Canada): Lake ecosystem response to the Holocene Thermal Maximum and drivers of mid-to-late Holocene climate variability

The importance of effective moisture and landscape controls on diatom assemblages and primary production in Roche Lake, British Columbia, Canada over the past ca. 1800 years

“…The IntCal13 14 C curve was used to calibrate 14 C age estimates (Reimer et al, 2013), and a continuous age-depth model was developed using the Bayesian age-modeling package rbacon v. 2.4.2 (Blaauw and Christen, 2011) in R (R Core Team, 2018). A 210 Pb estimated date (11 cm = AD 1951) was also included in the chronology based on correlation of the high-resolution diatom biostratigraphy with a gravity core taken from the same location (Mushet et al, 2022), while the surface level of the core (0–0.5 cm) was assigned to the year associated with coring.…”

“…Moreover, the high modern pH (∼8.5) and high Ca concentration (∼33 mg L −1 ) suggest that Roche Lake can produce authigenic carbonates under the right conditions. While some calcium-limited systems may undergo carbonate precipitation during wet periods due to enhanced groundwater inputs (Shapley et al, 2005;Nelson et al, 2011), we note that previous work has associated warm and dry periods with carbonate precipitation in Roche Lake (Mushet et al, 2022). In contrast, titanium (Ti) and potassium (K) are used as proxies for direct mass inputs to the lake from the watershed because they are strong indicators of lithogenic material (Cohen 2003;Kylander et al, 2011).…”

“…CAMS = Center for Accelerator Mass Spectrometry. * indicates date was obtained from 210 Pb analyses of a gravity core taken from the same coring location in 2016, which was then correlated to the composite piston core using high-resolution diatom biostratigraphy (Mushet et al, 2022).…”

“…The master sedimentary sequence was developed based on the overlap of the offset sequences identified from visible laminations, and high-resolution geochemical data obtained via μXRF. To determine whether the sediment-water interface of the piston core remained intact, we compared high-resolution diatom biostratigraphy to a 210 Pb-dated gravity core collected from the same location to investigate for coherent changes in species composition (Mushet et al, 2022). The final master sedimentary sequence (termed RLDM) from the cores from the deep basin of Roche Lake has a total length of 160 cm.…”

“…1), ~25 km southeast of Kamloops, BC, and is within the dry and cool subzone of the Interior Douglas Fir (IDF) biogeoclimatic zone. It is a relatively small lake, with a surface area of 134 ha and a maximum depth of 23 m. The Roche Lake catchment is ~3500 ha, and four small lakes flow into Roche Lake via one intermittent inlet (Mushet et al, 2022). Means of biweekly monitoring data collected between June 2015 and October of 2015 indicate it has a Secchi depth of 3.4 m, is meso-eutrophic (total dissolved phosphorus = 21 μg L −1 ), has a moderately high concentration of dissolved organic carbon (17 mg L −1 ), and experiences anoxia in the hypolimnion during the stratified period (~May–October) and following ice cover in the winter (~December–March) (Mushet et al, 2019).…”