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 equation

What 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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Present Ocean Food Web – Complex ecosystem interactions based on a low CO2 ocean

Microbial Remineralization

Primary Producers

Zooplankton Food WebUpper Trophic Levels

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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.