MaCS/SiMCo - Marine and Coastal Systems Master Program
Dinâmica Trófica Marinha – Marine Trophic Dynamics
Docentes/lecturers:
Helena Galvão
Sofia Gamito
Karim Erzini
Teórica 1 – Lecture 1
OCEAN FOOD WEBS
• What is Ocean Ecology?
– Interactions b/w oceanic organisms and their
environment
Described using FOOD Chains & FOOD Webs
- contain various Trophic levels (mode of Nutrition)
 Trophic FOOD Pyramids
may be based on numbers of BioMass and Energy
• Challenge Question
– What is Trophic Efficiency?
• Ratio of E in one trophic level / E vs next lowest trophic level
Et/Et-1
– Trophic efficiency represents efficiency of transfer of E b/w
trophic levels
– Provide theoretical basis for calculating productivity given
food web will support
» E.g. fisheries management
• IF Trophic Effeciency was say 10%
– How many calories of Copepods (zooplank) could be sustained from
?
• How many calories of anchovies could then survive from
• 10,000,000 calories of Phytoplakton
– 1,000,000 calories of copepods?
• Lindeman (1941) Defines an Ecosystem
– Challenge Question - What is it?
• “a system of Physical, Chemical and Biological processes
active within a space-time unit of any magnitude”
• Or Community of organisms and the abiotic factors
with which they interact
Bottom Up/Top down control
– Challenge Questions?
• What is the difference b/w
– Bottom Up,
– Top Down and
– Wasp waste control of Food Webs in Ocean Ecology
Top Down
Wasp/Waste
Bottom Up
• Seasonal (water temperature) changes along
Monterrey CA coast
– Influence fisheries distribution
– Wasp-Waste Control (middle trophic level control)
• Classical Food Web, Alistair Hardy (1924)
• The Microbial Food web (Azam et al. 1984)
– Marine bacteria
– A new perspective
•Representative Ocean Food Webs
• Upwelling Event – Food Web Dynamics (Food chain predominant)
• Representative Ocean Food Webs
– Upwelling Ecosystems
• Most productive in Worlds Oceans
• Good example of Transitional Food Chains
– Upwelled Nutrients  phyto blooms  zoo grazing  anchovies 
 large fish  seals  Sharks
– 10% Ocean Primary Productivity
– 20% worlds Fisheries Catch
•Representative Ocean Food Webs
• Marginal Ice Zone Ecosystem – Food Web Dynamics
(Food Chain predominant)
•Representative Ocean Food Webs
•Ice edge Ecosystem –spring/summer- Food Web Dynamics
•Representative Ocean Food Webs
• Pelagic food web Ecosystem – The Biological Pump
•Representative Ocean Food Webs
•Hydrothermal Vent – Food Web Dynamics
•Chemosynthesis!
• Representative Ocean Food Webs
• Confirming your knowledge
– Where are the 5 areas Major Oceanic Fisheries Industry?
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West Coast N. America
Peru Coast
N.W. Africa
S.W. Africa
Ethiopia
– What physical/chemical and biological factors cause
them to be so productive?
• Prevailing winds  upwelling of Nutrients  phyto blooms
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