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Published byKaia Purdon Modified over 10 years ago
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To recover or not to recover – the ”Laurentius-equation” Søren Laurentius Nielsen Roskilde University
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Original dataset based on: • 162 transects /stations • 23 areas • Data from years 1980 – 1991 • Data from the then Danish counties
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Spearman- Rank Correlation Coefficients – all significant
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Established these relationships: • Nutrients (N, P) → Phytoplankton biomass • Phytoplankton biomass + suspended matter → Secchi depth • Secchi depth → Eelgrass depth limit • TN → Eelgrass depth limit
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N and P vs. Phytoplankton biomass
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• The equations reflect a comparison between locations • Not a development over time • Later uses imply a place for time substitution • Variation caused by differences among locations in other factors
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Sediment characteristics suspected Krause-Jensen et al., Vand & Jord, 2007 Krause-Jensen et al., MEPS, 2011
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(it might get quite complicated…) Krause-Jensen et al., MEPS, 2011
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Causal links: N - loading N - concentrati on Phyto- plankton LightDepth limit Algal mats Organic matter Changes in sediment Anoxia Resus- pension
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Markager S., Carstensen J, Krause-Jensen D, Windolf J, Timmermann K. 2010. Technical report from NERI no. 787. http://www.dmu.dk/Pub/FR787.pdf http://www.dmu.dk/Pub/FR787.pdf Based on empirical analyses of data from Skive Fjord, Horsens Fjord and Odense Fjord
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Kemp et al. 2009 Hysteresis and regime shifts Duarte et al., Estuaries and Coasts, 2009
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Conceptual model Markager S., Carstensen J, Krause-Jensen D, Windolf J, Timmermann K. 2010. Technical report from NERI no. 787. http://www.dmu.dk/Pub/FR787.pdf http://www.dmu.dk/Pub/FR787.pdf
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Reasons for the hysteresis Causal links: N - loading N - concentrati on Phyto- plankton LightDepth limit Algal mats Organic matter Changes in sediment Anoxia Resus- pension
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3d dynamic model Sediment physics Sediment lability Benthic fauna Vegetation Wave & current energy Input Output Hydrodynamic simulation TD, sediment transport simulation Ecological simulation Erosion/deposition Bio-sedimentation
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