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Heike K. Lotze Dalhousie University Halifax, Canada

Land-Ocean Interactions: The known and unknown impacts of multiple human activities on marine biodiversity. Heike K. Lotze Dalhousie University Halifax, Canada. History of change in estuaries. NCEAS (National Center for Ecological Analysis and Synthesis). How to explore the Past.

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Heike K. Lotze Dalhousie University Halifax, Canada

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  1. Land-Ocean Interactions: The known and unknown impacts of multiple human activities on marine biodiversity Heike K. Lotze Dalhousie University Halifax, Canada

  2. History of change in estuaries NCEAS (National Center for Ecological Analysis and Synthesis)

  3. How to explore the Past • Paleontological records • Archaeological records • Historical records • Ecological records

  4. Methods • Cultural periods • Relative abundance

  5. Ecosystem degradation Lotze et al. in preparation

  6. Resource depletion and habitat loss Pristine Mammals Birds Abundant Depleted Rare Extinct Fish Reptiles Invert. Plants Lotze et al. in preparation

  7. Degradation of water quality • Sediment cores • Hydrographic data Lotze et al. in preparation

  8. Species invasion Lotze et al. in preparation

  9. Present state of degradation Relative abundance Lotze et al. in preparation

  10. Shifts in diversity Lotze et al. in preparation

  11. Human drivers Lotze et al. in preparation

  12. Recovery Lotze et al. in preparation

  13. The Future Where are we going?

  14. 1. Temporal acceleration How much will our impact increase before leveling off?

  15. Nutrient loading Since 1960: • Nitrogen flow in terrestrial ecosystems doubled • Phosphorus flow tripled Human-produced Reactive Nitrogen Millennium Ecosystem Assessment 2005

  16. Oxygen-depleted areas Global increase since 1900 Diaz et al. 2004, GEO Year Book 2003

  17. Harmful algal blooms Public health events Fish events Coral events Invertebrate events Mollusc events Sea turtle events Seagrass events Bird events Mammal events Harmful algal bloom Increase since 1970 HEED 1998

  18. Degradation of water quality Lotze et al. in preparation

  19. Diversity decline with eutrophication Eutrophication gradient Worm & Lotze, in press

  20. Ecosystem degradation

  21. Are we tipping the balance? The rise of slime…?

  22. 2. Spatial expansion How far will we spread our impacts?

  23. Rivers: nutrient loading Increase in Nitrogen transport to river mouths Millennium Ecosystem Assessment 2005

  24. Coasts: oxygen-starved zones Oxygen depletion key:  Annual / Episodic / Periodic / Persistent GEO Year Book 2003

  25. Coasts: harmful algal bloom HEED 1998

  26. Open ocean: atmospheric deposition Reactive nitrogen deposition in 1993 (mg N m-2 yr-1) Galloway and Cowling 2002

  27. Deep sea: nitrogen enrichment Deep-water Redfield ratio in North Atlantic Ocean exhibits rising N:P, possibly related to increased atmospheric N deposition Pahlow & Riebesell 2000, Science

  28. Reaching global limits? River => estuary => inshore => offshore => deep sea Global consequences…? Time • Nutrient loading • Exploitation • Habitat destruction

  29. 3. Multiplication How will our multiple impacts interact?

  30. Exploitation Filter feeder Pollution Filter Feeder Herbivores Climate change Annual algae Annual algae Rockweed Habitat destruction Nutrients Nutrient loading Acceleration of algal blooms Lotze & Milewski 2004

  31. Interacting climatic and ecological controls Increasing temperature enhances: • algal recruitment and growth • the nutrient effect • the grazing effect Lotze & Worm 2002

  32. Caribbean food web containing 30% of species and 11% of the interactions. Bascompte et al. 2005 Potential for surprises? Can we predict and manage multiple interactions among multiple human drivers and multiple species?

  33. 4. Sustainability How much un-degraded river, estuary, and inshore area do we needto sustain marine diversity and goods & services?

  34. Degraded estuaries

  35. Population declines In 22 out of 28 estuaries designated as National Estuary Programme sites in the USA, declines of fish and wildlife populations are now considered to be high or medium-priority problems Kennish 2002

  36. Strongly impacted coastal zones Kennish 2002

  37. Worse-case scenario: Can we do without them?

  38. Best-case scenario: Can we restore them?

  39. Reversing nutrient pollution • Tampa Bay, FL • 10-fold reduction of nitrogen loading from municipal waste • Increase in water clarity • Reduction of phytoplankton productivity • Reduction in cyanobacterial blooms • Recovery of seagrass Cloern 2001

  40. Reversing nutrient pollution • Thames and Forth River estuaries, UK • Increase in oxygen • Recovery of fish stocks Cloern 2001

  41. Conclusions The Known • Where we come from • Where we are today • Where we are going if current trends continue • Recovery is possible Thus, whatever the UU’s, we should use the K’s to act today and turn negative trends around.

  42. Thank you

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