Resilience and regime shifts in models and ecosystems

Global environmental changes have direct effects on aquatic ecosystems, as well as indirect effects through alterations of adjacent terrestrial ecosystem structure and functioning. For example, shifts in terrestrial vegetation communities resulting from global changes can affect the quantity and quality of water, organic matter, and nutrient inputs to aquatic ecosystems. The relative importance of these direct and terrestrial-vegetation-mediated effects is largely unknown, but understanding them is essential to our ability to predict the consequences of global changes for aquatic ecosystems. Here, we present a conceptual framework for considering the relative strengths of these effects and use case studies from xeric, wet and temperate, and boreal ecosystems to demonstrate that the responses of aquatic ecosystems to drivers of global changes may not be evident when the pathways are studied separately. Future studies examining changes in aquatic ecosystem structure and functioning should consider the relat...

Terrestrial ecosystem

Environmental change

Terrestrial plant

10.1525/bio.2010.60.8.5

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Simplifying complexity : reflections on ecosystems, psychiatric disorders and biogeochemical pathways

Ingrid A. van de Leemput

Nitrogen compounds are transformed by a complicated network of competing geochemical processes or microbial pathways, each performed by a different ecological guild of microorganisms.Complete experimental unraveling of this network requires a prohibitive experimental effort.Here we present a simple model that predicts relative rates of hypothetical nitrogen pathways, based only on the stoichiometry and energy yield of the performed redox reaction, assuming competition for resources between alternative pathways.Simulating competing pathways in hypothetical freshwater and marine sediment situations, we surprisingly found that much of the variation observed in nature can simply be predicted from these basic principles.Investigating discrepancies between observations and predictions led to two important biochemical factors that may create barriers for the viability of pathways: enzymatic costs for long pathways and high ammonium activation energy.We hypothesize that some discrepancies can be explained by nonequilibrium dynamics.The model predicted a pathway that has not been discovered in nature yet: the dismutation of nitrite to the level of nitrate and dinitrogen gas.+

Biogeochemical Cycle

10.18174/379242

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Climate induced biodiversity shifts in freshwater ecosystems : models and time series analysis

Marten Scheffer Elisa Benincà

Freshwater ecosystem

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AQUATIC ECOSYSTEMS AND GLOBAL CLIMATE CHANGE

Limnology and Oceanography Bulletin (2002)