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  1. Free, publicly-accessible full text available January 1, 2023
  2. Resilience was compared for alternate states of phytoplankton pigment concentration in two multiyear whole-lake experiments designed to shift the manipulated ecosystem between alternate states. Mean exit time, the average time between threshold crossings, was calculated from automated measurements every 5 min during summer stratification. Alternate states were clearly identified, and equilibria showed narrow variation in bootstrap analysis of uncertainty. Mean exit times ranged from 13 to 290 h. In the reference ecosystem, Paul Lake, mean exit time of the low-pigment state was about 100 h longer than mean exit time of the high-pigment state. In the manipulated ecosystem, Peter Lake, mean exit time of the high-pigment state exceeded that of the low-pigment state by 30 h in the cascade experiment. In the enrichment experiment mean exit time of the low-pigment state was longer than that of the high-pigment state by about 100 h. Mean exit time is a useful measure of resilience for stochastic ecosystems where high-frequency measurements are made by consistent methods over the full range of ecosystem states.
  3. Factors driving freshwater salinization syndrome (FSS) influence the severity of impacts and chances for recovery. We hypothesize that spread of FSS across ecosystems is a function of interactions among five state factors: human activities, geology, flowpaths, climate, and time. (1) Human activities drive pulsed or chronic inputs of salt ions and mobilization of chemical contaminants. (2) Geology drives rates of erosion, weathering, ion exchange, and acidification-alkalinization. (3) Flowpaths drive salinization and contaminant mobilization along hydrologic cycles. (4) Climate drives rising water temperatures, salt stress, and evaporative concentration of ions and saltwater intrusion. (5) Time influences consequences, thresholds, and potentials for ecosystem recovery. We hypothesize that state factors advance FSS in distinct stages, which eventually contribute to failures in systems-level functions (supporting drinking water, crops, biodiversity, infrastructure, etc.). We present future research directions for protecting freshwaters at risk based on five state factors and stages from diagnosis to prognosis to cure.
    Free, publicly-accessible full text available March 16, 2023
  4. null (Ed.)
    Abstract. Biogeochemistry has an important role to play in manyenvironmental issues of current concern related to global change and air,water, and soil quality. However, reliable predictions and tangibleimplementation of solutions, offered by biogeochemistry, will need furtherintegration of disciplines. Here, we refocus on how further developing andstrengthening ties between biology, geology, chemistry, and social scienceswill advance biogeochemistry through (1) better incorporation of mechanisms,including contemporary evolutionary adaptation, to predict changingbiogeochemical cycles, and (2) implementing new and developing insights fromsocial sciences to better understand how sustainable and equitable responsesby society are achieved. The challenges for biogeochemists in the 21stcentury are formidable and will require both the capacity to respond fast topressing issues (e.g., catastrophic weather events and pandemics) andintense collaboration with government officials, the public, andinternationally funded programs. Keys to success will be the degree to whichbiogeochemistry can make biogeochemical knowledge more available to policymakers and educators about predicting future changes in the biosphere, ontimescales from seasons to centuries, in response to climate change andother anthropogenic impacts. Biogeochemistry also has a place infacilitating sustainable and equitable responses by society.