Land-Ocean Interactions:
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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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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

  • Paleontological records

  • Archaeological records

  • Historical records

  • Ecological records


Methods

  • Cultural periods

  • Relative abundance


Ecosystem degradation

Lotze et al. in preparation


Resource depletion and habitat loss

Pristine

Mammals

Birds

Abundant

Depleted

Rare

Extinct

Fish

Reptiles

Invert.

Plants

Lotze et al. in preparation


Degradation of water quality

  • Sediment cores

  • Hydrographic data

Lotze et al. in preparation


Species invasion

Lotze et al. in preparation


Present state of degradation

Relative abundance

Lotze et al. in preparation


Shifts in diversity

Lotze et al. in preparation


Human drivers

Lotze et al. in preparation


Recovery

Lotze et al. in preparation


The Future

Where are we going?


1. Temporal acceleration

How much will our impact increase

before leveling off?


Nutrient loading

Since 1960:

  • Nitrogen flow in terrestrial ecosystems doubled

  • Phosphorus flow tripled

Human-produced Reactive Nitrogen

Millennium Ecosystem Assessment 2005


Oxygen-depleted areas

Global increase since 1900

Diaz et al. 2004, GEO Year Book 2003


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


Degradation of water quality

Lotze et al. in preparation


Diversity decline with eutrophication

Eutrophication gradient

Worm & Lotze, in press


Ecosystem degradation


Are we tipping the balance?

The rise of slime…?


2. Spatial expansion

How far will we spread our impacts?


Rivers: nutrient loading

Increase in Nitrogen transport to river mouths

Millennium Ecosystem Assessment 2005


Coasts: oxygen-starved zones

Oxygen depletion key:  Annual / Episodic / Periodic / Persistent

GEO Year Book 2003


Coasts: harmful algal bloom

HEED 1998


Open ocean: atmospheric deposition

Reactive nitrogen deposition in 1993 (mg N m-2 yr-1)

Galloway and Cowling 2002


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


Reaching global limits?

River

=> estuary

=> inshore

=> offshore

=> deep sea

Global consequences…?

Time

  • Nutrient loading

  • Exploitation

  • Habitat destruction


3. Multiplication

How will our multiple impacts interact?


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


Interacting climatic and ecological controls

Increasing temperature enhances:

  • algal recruitment and growth

  • the nutrient effect

  • the grazing effect

Lotze & Worm 2002


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?


4. Sustainability

How much un-degraded river, estuary,

and inshore area do we needto

sustain marine diversity and

goods & services?


Degraded estuaries


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


Strongly impacted coastal zones

Kennish 2002


Worse-case scenario:

Can we do without them?


Best-case scenario:

Can we restore them?


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


Reversing nutrient pollution

  • Thames and Forth River estuaries, UK

  • Increase in oxygen

  • Recovery of fish stocks

Cloern 2001


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.


Thank you


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