Structure and Function of Marine Ecosystems

Steven Murawski Ph.D.Director, Office of Science & TechnologyNational Marine Fisheries Service

Challenges of Integrating Ecosystem Knowledge Definitions Key Processes in Marine Ecosystems Status of Ecosystem Science

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DefinitionsDefinitionsAn An ecosystemecosystem is a geographically specified system of organisms is a geographically specified system of organisms (including humans), the environment, and the processes that control its (including humans), the environment, and the processes that control its dynamics. dynamics.

The The environmentenvironment is the biological, chemical, physical, and social is the biological, chemical, physical, and social conditions that surround organisms.conditions that surround organisms.

When appropriate, the term When appropriate, the term environment should be environment should be qualified as biological, qualified as biological, chemical, physical, and/or chemical, physical, and/or social.social.

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Spatial Scales & Boundaries

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Phytoplankton

Zooplankton

Forage Fish

Piscivores

Apex Predators

Humans

The Trophic Pyramid and Energy Flow

1000 units

100 units

10 units

1 unit

0.1 unit

0.01 unit

If transfer efficiency is 10%-5-

Photosynthesis occurs primarily in waters less than 200 meters deep, which make up about 7% of the World’s Oceans

below 200 m, nutrients accumulate and must bebrought to the surface in order to support production- by upwelling & currents -6-

Scales and Observations

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Regional Climatology Affects Ecosystems

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Interactions Between Physical &Biological Components of Ecosystems

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Harvesting Affects Distributions & Abundances of Species

Atlantic cod

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Known

Unknown

Unknowable

Surface Production & Dynamics

Status of Major Species

Number of Species inthe Oceans

Structure of “pristine” ecosystems

3-D Structure of SelectedOcean Environments

Evolutionary effectsof human activitiesSynoptic Maps of the

Sea Floor

Food-web and particle size models

Valuing EcosystemGoods & Services

Climate Variation effects onspecies & ecosystems

Spatially-explicit models ofpredator-prey systems

Status of all “important” species

Mapping of Habitats

Predictive models ofmany-species interactions

NutrientEnrichment & Toxics

Reversibility ofHuman impacts