The fossil record of freshwater dinoflagellates and green algae in paleoenvironmental studies

点击翻译按钮获取中文摘要

Non-pollen palynomorphs (NPP) in a single “pollen slide” provide information about the entire lake ecosystem and surrounding watershed. Despite their common presence, even in sediments that lack mineralized microfossils, algal palynomorphs are typically ignored or mentioned in passing by pollen analysts. My students and I will combine phycological/ limnological and palynological/ paleolimnological approaches to promote their use as paleolimnological proxies by studying: 1) the taxonomy of algal palynomorphs, using germination studies and rDNA sequencing, in collaboration with H Gu (Xiamen). These findings will be applied to studies of the evolution of freshwater algae in collaboration with various colleagues aw well as to our paleolimnological studies.2) the environmental control on algal palynomorphs, relating lakebed assemblages to measured environmental variables. A key aspect of the proposed research is to expand the calibration dataset beyond the 30 lakes in the Experimental Lakes Area of NW Ontario to other parts of eastern North America; this will investigate the significance of climate and geology on the palynological record, with the aim of developing regional transfer functions to allow quantitative reconstruction of water quality. Intrabasinal studies will also be conducted to assess variability across Lake George NY, in a multiproxy investigation with collaborators from Rensselaer Polytechnic (RPI).3) the taphonomic factors that skew the palynological record relative to the phycological record, comparing lakebed samples with sediment trap and plankton tow assemblages at different times of year in lakes that vary in size, depth, geology, hydrology, human impact on the lake and watershed, etc. Continued seasonal sampling by PhD student A Krueger (including traps recently deployed at continuous-monitoring sites in the large, oligo-mesotrophic Lake George) will allow us to relate lakebed sediments to phytoplankton productivity over multiple years and to measured limnological parameters. Collaboration with researchers studying zooplankton and other phytoplankton groups will provide insights into the “top-down” effects of predation and competition on algal populations. These findings will then be applied to downcore and outcrop studies to reconstruct limnological changes associated with both warmer (last interglacial) and drier (8.2 k event) climates and with human impact. This will allow us to assess the impact of projected climate change and population growth on water quality and quantity in the Great Lakes region. Improved understanding of the spatial distribution of NPP and taphonomy will also be applied to studying unusual sedimentation events in organic-rich lakes, allowing us to assess the use of NPP as proxies of sudden-impact natural hazards. This will have potential applications for paleoseismological and paleotempestological studies.