Biological Productivity
Conditions for Life in the Sea
Consider the main biochemical reaction for life in the sea, and on earth in general:
6H2O + 6CO2 + energy + nutrients = C6H12O6 + 6O2
Focus on left side of equationWhat is in short supply in the sea and thus
limits the amount of life in the ocean??
Absorbing Nutrients 6H2O + 6CO2 + energy + nutrients = C6H12O6 + 6O2
Phytoplankton are base of the food chain
Most important primary producers of complex sugars and oxygen
Lauderia sp.
Open Ocean Food Webs
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Copepods
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Present Ocean Food Web – Complex ecosystem interactions based on a low CO2 ocean
Microbial Remineralization
Primary Producers
Zooplankton Food WebUpper Trophic Levels
Seafloor community
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Absorbing Nutrients Nutrients absorbed by
plants through diffusion across a semi-permeable membrane
Lauderia sp.
Diffusion:molecules move from high to low concentrations
Which Nutrients are in Short Supply?
Nitrogen (N) as Nitrate NO3 (-2) Phosphorus (P) as Phosphate PO4 (-2) Silicon (Si) as Silicate SiO4 (-2)
Phosphate and Nitrate in the Pacific
Silicate in the Pacific
Biolimiting Nutrients N, P, and Si are exhausted first in Eq.
surface waters during photosynthesis Essential to the growth of phytoplankton If these biolimiting nutrients increase in
sea water, life increases If these biolimiting nutrients decrease in
sea water, life decreases Where would you expect to find the
highest biomass in the Pacific??
CZCS Global Primary Production
O2 is high in the surface and mixed layer
O2 decreases to a minimum at base of thermocline
O2 then steadily increases with depth
How Does Nutrient Distribution Compare w/Dissolved Oxygen?
6H2O + 6CO2 + energy + nutrients = C6H12O6 + 6O2
Dissolved O2 Reverse of Nutrients
Why is the Concentration of Oxygen High in the Mixed Layer??
Hint #1: How and where is oxygen produced in the sea???6H2O + 6CO2 + energy + nutrients = C6H12O6 + 6O2
Hint #2: How can oxygen be mixed downward from the atmosphere into the ocean?
How is Oxygen Removed from the Thermocline & Slightly Below??
Dead and decaying organic matter sinks downward from surface waters
Rate of sinking decreases as it encounters the cold, dense water of the thermocline
Material decays (oxidizes) at the thermocline, which strips O2 out of the water and returns nutrients to the sea
Cold, nutrient-rich water of the thermocline is returned to sunlit surface waters by way of upwelling
CZCS Global Primary Production
Marine Ecology
Basic Ecology physical and chemical parameters
affecting distribution and abundance An ecosystem includes both the living
(biotic) and non-living (abiotic) portions of the environment.– Examples include: salt marshes, estuaries,
coral reefs, the North Pacific Gyre.
Classification of Organisms by Environment
horizontal: neritic | oceanic vertical:
– epipelagic (top) / euphotic (good)– mesopelagic (middle) / disphotic (low)– bathypelagic (deep) / aphotic (without)– abyssopelagic (“bottomless”)
Divisions of the Marine EnvironmentFigure 9-1
Classification of Organismsby Lifestyle
Scientists have established another classification scheme to categorize biota on the basis of lifestyle. The major groups are:– plankton (floaters)– nekton (swimmers)– benthos (bottom dwellers)
Plankton weak swimmers, drifters, unable to
counteract currents. – Phytoplankton (plants)– Zooplankton (animals)
Nekton active swimmers capable of counteracting
currents. – Fish– Squids– Reptiles– Birds– Mammals
Distribution of Marine Lifestyles
16.7% of Earth’s animals are marine 2% inhabit pelagic environment (most of
the oceans are cold and dark) 98% are benthic!
Benthos Epiflora or epifauna live on the sea
bottom. Infauna live in the sea bottom. Benthic plants - restricted to shallow
waters (light) Benthic animals occur everywhere from
shallow depths to the deep sea.
Research Video Clips:“Live fast, die young...”
Hydrostatic Pressure Pressure caused by the height of water. Function of water height and water density Pressure generally increases at a rate of 1
atm per 10 m of water.( or 16 psi per 10 m depth)
Think You’re Under Pressure Now?
Hydrostatic Pressure(Cont.)
enormous in the deep sea yet animals live there.
Animals do not contain gases. However, mesopelagic fish which have
gas-filled swim bladders to help maintain neutral buoyancy – unable to move rapidly between depths– pressure change could cause bladder explode.
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