Introduction to Marine Habitats

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Introduction to Marine Habitats
FISH 420/520 Spring 09
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Terrestrial Biomes
Grassland
Tundra
Desert
Forest
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What are the marine biomes?

How might they be defined?
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Towards a Classification of Marine Biomes

• Yentsch and Garside
• Asked whether patterns of pelagic biogeography
  were a response to patterns of primary production
• In other words, biomes can be established by
  similarities in physical forcing of algal growth
• Alan Longhurst took this idea and formulated 4
  pelagic ocean biomes

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What limits Algal Production? (1) Light
Consider a vertically mixed ocean
Light
compensation depth Photosynthesis Respiration
Depth
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What Limits Primary Productivity? (2) Nutrients
Stratified Ocean Condition
Temp
Depth
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Areas of high production must have the following

• Restricted vertical displacement of primary
  producers
• External nutrient source or highly efficient
  nutrient cycling

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Two primary ways this happens
Upwelling Tidal Fronts / Mixing
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Upwelling 101
Ekman Transport
Coastal Upwelling
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Principal Surface Currents
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Sea Surface Temperature
These four areas, which account for only 1 of
surface area, account for 20 of fishery landings
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The coldest winter I ever saw was the summer I
spent in San Francisco Mark Twain
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Depth of the mixed layer is crucial
Cool Water / Anchovy Regime
Warm Water / Sardine Regime
Strong Trade Winds
Weak Trade Winds
Longitude
Longitude
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Upwelling systems tend to be on western edge of
continents
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Tidal Mixing on Continental Shelves
70 of fisheries production occurs on
non-upwelling, continental shelf systems
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Georges Banks and Tidal Mixing
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Tidal Fronts and Mixing on Continental Shelf and
Seamounts
Warm, low-nutrient water
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Well Mixed
10
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Cold, high-nutrient water
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Tidal Fronts and Mixing on Continental Shelf and
Seamounts
265 mg C m-2 h-1
210 mg C m-2 h-1
160 mg C m-2 h-1
Warm, low-nutrient water
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10
Tidal Flow
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Well-Mixed
Cold, high-nutrient water
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What are the biomes then?

• Longhurst proposed the following
• Trades Biome
• mixed layer depth forced by large scale wind
  forcing
• Westerlies Biome
• mixed layer depth forced by local winds and
  irradiance
• Polar Biome
• mixed layer constrained by surface brackish water
• Coastal
• mixed layer forced by diverse coastal processes

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Principal Surface Currents
Polar Biome
Westerlies Biome
Trades Biome
Westerlies Biome
Polar Biome
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The coastal biome is extremely diverse
Continental shelf Estuaries Coral Reefs
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Other components of Estuaries

• Salt Marshes
• Sea grasses
• Mangroves

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Classic Estuarine Circulation
Animation from www.chemgapedia.de
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What about coral reefs?

• Among the most productive marine habitats
• Yet, exist in regions that are generally nutrient
  poor
• Indo-Pacific
• Caribbean
• Two reasons for this
• Shallow
• Extremely efficient nutrient cycling

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Productivity and Predictability of Marine Habitats
Coral Reefs
Estuaries
Continental Shelf
Coastal Upwelling
Predictability
Open Ocean
100
1000
300
Productivity (g C m-2 y-2)