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REDFIELD RATIOS
5
REDFIELD RATIOS
Carlotta De Blasi M7400001
NUTRIENTS
NUTRIENTS
Dissolved substance in the water from
which organisms can obtain an essential element for growth
-Na; Ca;S;C
-N; P; Si; Fe
UNITS: μmol/Kg,
μmol/l
MARINE VS TERRESTRIAL
-No steams or stalks
-Smaller size
-Ephimeral nature
REDFIELD RATIOS
Data collected by :
- "Dana"
- "Atlantis" : seven stations in the western Atlantic Ocean.
NITRATE VS PHOSPHATE
N-P
- Any gain or loss in nitrate content is accompanied by a strictly proportional gain or loss in phosphate content;
- For every three grams of nitrogen, one gram of P04
- 20 atoms of nitrogen to 1 atom of phosphorus.
NITRATE VS O2 UTILIZED
N-O2
- The correlation between the gain in concentration of nitrate and the loss in concentration of oxygen, is almost equally good
- Proportion of 1 millimol of nitrate to 6 millimols of oxygen.
NITRATE VS CARBONATE
N-CO2
- The correlation is less precise due to the greater variation in the carbonate measurements.
- Ratio of I millimol of nitrate to 7 of carbonate.
PLANKTON VS SEA WATER
OBSERVATIONS
The proportions of carbon, nitrogen, and phosphorus as calculated from the sea are not greatly different from those observed in various plankton.
EXPLANATIONS
- Balancing of plankton communities
- Activities of nitrogen-fixing bacteria
ELUCIDATION
- The Redfield ratio is the ratio in which different chemical elements are present in average plankton biomass
- C:N:P ratio of 106:16:1 canonical Redfield ratio
- Not ratios between absolute concentrations, but among variations of N, P or C
- UTILIZATION RATIOS
- Balance between photosynthesis and remineralization
BEYOND
Extendet to other elements
Extended
oligoelements
ex. For each 7.5 atoms of Fe, 1001 of P
>0 More N than P <0 Less N than P
Redfield still valid
REGIONAL
PATTERNS
N*
REGIONAL PATTERNS
INFLUENCED BY:
-BIOLOGICAL ACTIVITY
-ENVIRONMENTAL CONDITIONS
The limit concentration and the limit compositional ratio are species-specific
(ORGANISMS PLASTICITY)
PECULIAR PATTERN
MED SEA
Anomalous Redfield ratio, with a slope different from the canonical 16.
Excess of N compared to P
WM N:P -20
EM N:P >25
REMOVAL OF PHOSPHATE
Sinking toward the bottom of the phosphate attached to dust particles
SINKs
LOW DENITRIFICATION RATES
Bacteria avoid the competition due to the oxygen rich environment
NITROGEN FIXATION
- Low values of δ 15N in the EM
- High values of Si in the Em
Phospate limited environment
SOURCEs
UNBALANCED INPUTS
ATI( Atmospheric and Terrestrial Inputs) contribute to the stocks with high values on N and low values of P