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To recover or not to recover – the ”Laurentius-equation” Søren Laurentius Nielsen Roskilde University.

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Presentation on theme: "To recover or not to recover – the ”Laurentius-equation” Søren Laurentius Nielsen Roskilde University."— Presentation transcript:

1 To recover or not to recover – the ”Laurentius-equation” Søren Laurentius Nielsen Roskilde University

2 Original dataset based on: • 162 transects /stations • 23 areas • Data from years 1980 – 1991 • Data from the then Danish counties

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4 Spearman- Rank Correlation Coefficients – all significant

5 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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8 N and P vs. Phytoplankton biomass

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12 • 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

13 Sediment characteristics suspected Krause-Jensen et al., Vand & Jord, 2007 Krause-Jensen et al., MEPS, 2011

14 (it might get quite complicated…) Krause-Jensen et al., MEPS, 2011

15 Causal links: N - loading N - concentrati on Phyto- plankton LightDepth limit Algal mats Organic matter Changes in sediment Anoxia Resus- pension

16 Markager S., Carstensen J, Krause-Jensen D, Windolf J, Timmermann K Technical report from NERI no Based on empirical analyses of data from Skive Fjord, Horsens Fjord and Odense Fjord

17 Kemp et al Hysteresis and regime shifts Duarte et al., Estuaries and Coasts, 2009

18 Conceptual model Markager S., Carstensen J, Krause-Jensen D, Windolf J, Timmermann K Technical report from NERI no

19 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

20 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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