Publications by authors named "Mark J Lisac"
Observational data from the past century have highlighted the importance of interdecadal modes of variability in fish population dynamics, but how these patterns of variation fit into a broader temporal and spatial context remains largely unknown. We analyzed time series of stable nitrogen isotopes from the sediments of 20 sockeye salmon nursery lakes across western Alaska to characterize temporal and spatial patterns in salmon abundance over the past ∼500 y. Although some stocks varied on interdecadal time scales (30- to 80-y cycles), centennial-scale variation, undetectable in modern-day catch records and survey data, has dominated salmon population dynamics over the past 500 y.
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- Humans have significantly increased the levels of reactive nitrogen (Nr) in the environment, mainly through industrial activities, affecting ecosystems even in remote areas.
- Research on nitrogen stable isotopes in sediments from 25 Northern Hemisphere lakes indicates a distinct spike in nitrogen sources starting around 1895, aligning with rising CO2 emissions.
- Despite low current nitrogen deposition in these isolated regions, the long-term impact of human activity suggests that anthropogenic nitrogen has been influencing the nitrogen budget of watersheds for over a century.