YahelCO11_10 Plankton stoichiometry and Redfield ratio-Rec

Chemical Oceanography – 10 Organic Matter Production and Remineralization: I. Plankton stoichiometry and Redfield ratios:

Chemical Oceanography – 10 Organic Matter Production and Remineralization: I. Plankton stoichiometry and Redfield ratios Gitai Yahel The School of Marine Sciences Ruppin Academic Center Gitai Yahel (Yahel@Ruppin.ac.il), Tel.( 09)830 4110 , Skype gitaiyahel, Web http://Moodle.Ruppin.ac.il

Slide 2:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 2 ) The great biogeochemical loop Photosynthesis converts dissolved inorganic chemicals into organic matter Remineralization converts organic matter back into dissolved inorganic matter Gruber & Sarmiento (2002) NO 3 , PO 4 NO 3 , PO 4

Mass and Energy Transfer – a simplified ecosystem model:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 3 ) Mass and Energy Transfer – a simplified ecosystem model After Dawn Wright and Bob Duncan Sun light energy is converted to order (living forms) and eventually lost as heat

Slide 4:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 4 ) Mass and Energy Transfer II After Dawn Wright and Bob Duncan What happen to the matter?

Slide 5:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 5 ) Mass and Energy Transfer III After Dawn Wright and Bob Duncan

Slide 6:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 6 ) Energy loss Conservation of mass After Dawn Wright and Bob Duncan

A useful way to keep track of biomass in the lower trophic levels is to follow the path of MACRONUTRIENTS:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 7 ) Carbon C Source: Atmosphere Nitrogen N Source: Atmosphere Phosphorus P Source: Terrestrial (mostly rivers) A useful way to keep track of biomass in the lower trophic levels is to follow the path of MACRONUTRIENTS Redfield A.C. (1934) On the proportions of organic derivations in seawater and their relation to the composition of plankton . In James Johnson Memorial Volume. (ed. R.J. Daniel). University Press of Liverpool, pp. 177-192.

Redfield and the concept of Ecological stoichiometry :

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 8 ) Redfield and the concept of Ecological stoichiometry "In 1934, Alfred Redfield wrote a now classic paper in which he proposed that the N:P ratio of plankton (16:1) causes the ocean to have a remarkably similar ratio of dissolved NO 3 and PO 4 . This hypothesis suggested that, devoid of life, the chemical composition of the oceans would be markedly different. The concept of Refield ratios has been fundamental to understanding of the biogeochemistry of the oceans ever since." ( Falkowski & Davis, Nature 2004, 431:131) Understanding the stoichiometric ratios with which living things generate organic matter is central to understanding key global biogeochemical cycles ( C , N, P, S. etc’)

Redfield Ratio – The constant composition of plankton and its effect on the ocean chemistry:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 9 ) Redfield Ratio – The constant composition of plankton and its effect on the ocean chemistry Partly after Z. Johnson, SOEST All organisms are composed, primarily of a mixture of six major elements: hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulphur. Marine plankton are functionally similar ensembles of metabolites, often encased in a shell formed from the most readily available ingredients. Falkowski and Davis 2002 Ribosomal RNA Proteins Ribosomal RNA is correlated to growth rate Proteins are correlated to uptake and fixation mechanisms (of C,N,P)

The Redfield ratio (cont.):

Wednesday, February 23, 2011 Chemical Oceanography , Yahel@Ruppin.ac.il ( 10 ) The Redfield ratio (cont.) Redfield et al. argued that the similarity between the average nitrogen-to-phosphorus ratio in plankton (N:P=16 by atoms) and in deep oceanic waters (N:P=15) is neither a coincidence, nor the result of the plankton adapting to the oceanic stoichiometry, but rather that: phytoplankton adjust the N:P stoichiometry of the ocean to meet their requirements through nitrogen fixation Redfield Ratio (C:N:P) (molar ratio) = 106: 16 : 1 * average of all living material Redfield 1958 PO 4 No 3

The Redfield ratio II - C:N:P=106:16:1:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 11 ) The Redfield ratio II - C:N:P=106:16:1 Ratio of: Nutrients available (inorganic) Nutrient uptake ratio Composition of cells Useful for: Modeling Predicting limiting nutrient Suggests that biology is controlling the chemical constituency of the oceans Can be extended to include other elements e.g., H:O :C:N:P: Fe:VitB 12 Phosphorus 4000 Nitrogen 1000 Redfield 1958 Each class of compounds has its own unique stoichiometry: carbohydrates are C rich but N and P poor proteins are C and N rich but P poor nucleotides are rich in both N and P Questions: Why 16:1? Why not 6:1 or 60:1? How does an organism end up with a certain composition? What happens if one constituent is not available in adequate amounts ? Some answers – next year…

N&P distribution is a result of light driven biological interactions:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 12 ) N&P distribution is a result of light driven biological interactions Surface uptake by biological production & deep remineralization loop  Nutrient like gradients 106 C O 2 +16 H N O 3 + H 3 P O 4 + 78 H 2 O  C 106 H 175 O 42 N 16 P 1 + 150O 2 Dissolved Particulate

The Redfield ratio III – Nutrients limitations:

Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 13 ) The Redfield ratio III – Nutrients limitations Most of the ocean is N limited (was?, more next year) Costal eutrophic systems are often P limited Most lakes are P limited Mediterranean Sea is P (or N&P) limited Nitrate is depleted before phosphate is depleted N limited (pre 90s Pacific) P limited (Atlantic) 106 CO 2 +16 HNO 3 + H 3 PO 4 + 78 H 2 O  C 106 H 175 O 42 N 16 P 1 + 150 O 2

The Redfield ratio – current understanding:

The Redfield ratio – current understanding Fixed N:P ratios in the deep water of large water bodies (oceans, large lakes) are usually close to the Redfield ratio N:P ratios of phytoplanktonic taxa range from 6 to >50 Wednesday, February 23, 2011 Chemical Oceanography, Yahel@Ruppin.ac.il ( 14 ) Klausmeier et al. NATURE |VOL 429 | 2004 It is not clear if the 16:1 ratio represent: a physiological optimum? a balance between growth (low N:P) and competition (high N:P)? (iron) limitation on nitrogen fixation Note that the later hypothesis suggests that in an iron replete ocean the “Redfield ratio” may be mach higher Growth requires massive ribosomal (P based) production  low N:P Competition for nutrients or lights requires (N based) proteins based acquisition and fixation mechanisms  high N:P