Identifying Regional Hotspots of Biodiversity Change Over the Past ~150 Years: Beta-diversity of Diatom Assemblages from ~400 US Lakes

English Abstract:

There is growing acceptance that, over the past ~200 years, humans have fundamentally changed the functioning of the Earth’s key processes. However, at present it is less clear how diversity has been altered over this period. Here we use the USEPA National Lake Assessment program, an open access database containing data from over 1000 lakes, including lake sediment records (~400 lakes), to explore questions of regional aquatic diversity change. The focus of this project therefore, is to compare diatom assemblages from pre-industrial (where possible) or baseline sediments, to those found in modern (2007) sediments, generating estimates of beta-diversity. Our specific objectives are to: (1) Quantify patterns in latitudinal richness across lakes and regions with different disturbance histories, testing the hypothesis that latitude as a weaker effect on diatom (alpha) diversity in modern sediments relative to pre-1850 sediments, (2) Map diatom beta-diversity through both time (bottom and surface sediment core samples) and space (between lakes), creating a visual depiction of beta-diversity hot spots across the US, and (3) Relate landscape-level anthropogenic changes/trends to diatom diversity and beta-diversity as well as functional diversity, with a particular focus on alterations that influence lakeshore condition. We have found longitudinal richness patterns with both pre-industrial and modern sediments as well as regional differences in beta-diversity. Additionally, high beta-diversity is more related to species replacement through time or across a landscape than species loss. This work will contribute to an understanding of how landscape-scale changes affect diatom (plankton) alpha and beta diversity across the US, through the combination of both long-term monitoring and paleolimnogical data.