Ciclo do azoto no ambiente marinho

(1)

Produtores e bacérias N2 dissolvido NH4 DIN Terra NH3 Azoto particulado Sedimentos Guano, pescas Azoto Atmosférico DON NO3 NH4 fixado DON N part. não-vivo Desnitrificação Morte Regeneração Decomp. Excreção Regeneração Adsorção Troca iónica Nitrificação Amónificação Desnitrificação Decomp. Decomp. Absorção Uptake Fixação _Pastagem Sedimentação Fontes telúricas Volatilização Hetero. Consumidores

Ciclo do azoto no ambiente marinho

(2)

Transformações de azoto

Azoto

orgânico Uptake e redução _{assimilativa nas}

células Redução dissimilativa Fixação de N₂ Excreção Decomposição Uptake Nitrificação Nitrificação NH₄+ Azoto amoniacal NH₂OH Hidroxil amina N₂ Azoto gasoso N₂O Óxido nitroso NO Óxido nítrico NO₂ -Nitrito NO₃ -Nitrato 3 5 Estado de oxidação -3 -1 0 1 2

(3)

GIS

-

Annual mean DIN in the Tagus estuary

Limit of salt intrusion Lisboa Atlantic ocean 0 10 20 km DIN (umol l-1₎

(4)

NO3

NO3--Temperature relationship for the eastern Temperature relationship for the eastern tropical Pacific (Aug.

tropical Pacific (Aug.--Nov. 86Nov. 86--88)88)

n = 5035 50 40 Nitrate µ 20 30 M 10 0 ₁₀ ₂₅ ₃₀ 5 15 20 35 Temperature oC Fiedler

(5)

Redfield ratio

Definitions

z

z “Standard” ratio of C:N:P“Standard” ratio of C:N:P

z

z May be expressed in atoms or massMay be expressed in atoms or mass

z

z Derives from the constancy of composition of biotaDerives from the constancy of composition of biota

z

z C:N:PC:N:P 106:16:1106:16:1 (in atoms)(in atoms)

z

z C:N:PC:N:P 45:7:145:7:1 (in mass)(in mass)

z

z Oxygen may also be included, considering that for every Oxygen may also be included, considering that for every carbon atom fixed two oxygen atoms are produced

carbon atom fixed two oxygen atoms are produced

CO₂ + 2H₂A Light CH₂O + 2A + H₂O

Pigments

O:C:N:P

(6)

PO4

PO4 -- NO3 relationship for the easternNO3 relationship for the eastern tropical Pacific (Aug.

Phosphate µM 0 1 2 3 4 0 10 20 30 40 Nitrate µM 50 n = 5338 Fiedler

(7)

SiO4

SiO4 -- NO3 relationship for the easternNO3 relationship for the eastern tropical Pacific (Aug.

0 20 40 60 0 Silicate µM 10 20 30 40 Nitrate µM 50 n = 5324 Fiedler

(8)

N:P ratio for the Tagus Estuary

–

Data from B2K

60 70 80 n=1841 45 stations ~20 years DI N ( µmol L -1 ) 100 90 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 PO₄3- ₍_{µmol L}-1₎

(9)

N:P ratio for Carlingford Lough

80 100 n=859 73 stations 4 years (1990-1993) DI N ( µmol L -1 ) 120 60 40 20 0 0 1 2 3 4 5 PO₄3- ₍_{µmol L}-1₎ Data from BarcaWin2000

(10)

N:P ratio for Carlingford Lough

Seasonal breakdown

n=859

73 stations

4 years (1990-1993)

N/P ratio (no units)

0 2 4 6 8 10 12 14 16 18 20 0 50 100 150 200 250 300 350 400 Strong N limitation Julian day

(11)

Limit of salt intrusion Lisboa Atlantic ocean 0 10 20 km

GIS

-

Annual mean DIP in the Tagus

estuary

(12)

Limit of salt intrusion Lisboa Atlantic ocean 0 10 20 km

GIS

-

Annual mean Redfield ratio (N/P)

for the Tagus estuary

(13)

Balanço de massa de cargas e regeneração de nutrientes em Narragansett Bay, E.U.A.

Entradas anuais (106 _{at-g ano}-1₎ Azoto Fósforo Entradas Fixação 0.2 -Precipitação 2.8 0.19 Runoff 16.2 0.8 Rios 235 17.3 Efluentes 278 21.7 • Total 532 39.9 Regeneração Menhaden 0.8 0.1 Ctenóforos 8.1 0.8 Zooplâncton 98.5 -Bentos 264 41.1 • Total 371 42

Nixon, 1981. Remineralization and nutrient cycling in coastal marine ecosystems. In Neilson & Cronin (Eds.) , Estuaries and Nutrients, Humana, p. 111-138.

(14)

Balanço de massa de azoto. Todos os valores em kg N ano-1 Sippewissett marsh, E.U.A.

Entradas Saídas Trocas

líquidas

Precipitação 380 380

Águas subterrâneas 6120 6120

Fixação de N2 3280 3280

Trocas pela maré 26200 31600 -5350

Desnitrificação 6940 -6940 Sedimentação 1295 -1295 Outras 9 26 -17 • Total 35990 39860 -3870 % de troca biótica 9 18 % de troca física 91 82

Valiela & Teal (1979). The nitrogen budget of a salt marsh ecosystem, Nature 280, 652-656. Sinais menos indicam exportação do sapal.

(15)

DIN mass balance for Cala do Norte (kg N y

--11

₎

Advection-dispersion Internal processes

Inputs Upstream 817642 Effluents 3109278 Sub-total 3926920 Outputs Downstream -3607087 Sub-total -3607087 Total 319833 Sources Phyto mortality 29740

Zoo sloppy grazing 2819

Zoo metabolism 9632

Zoo excretion 321

Zoo mortality 1527

Sub-total 44039 Sinks

Gross primary prod. -363834 Sub-total -363834

Total -319795

(16)

Phytoplankton N mass balance for Cala

do Norte (gN m

--22

_y

--11

₎

Advection-dispersion Internal processes

Sources

Net primary prod. 20.53

Sub-total 20.53 Sinks Natural mortality - 2.73 Grazing - 1.44 Sub-total - 4.17 Total 16.36 Inputs Upstream 11.88 Sub-total 11.88 Outputs Downstream - 28.24 Sub-total - 28.24 Total - 16.36 Total 0 g m-2 _y-1 _Stock _{0.150 gN m}-2

(17)

Redfield ratio

Caveat

This is a mean ratio, in some cases the variance will

be large!

Applications

z

z Analysing the food chain (planktonic or detrital)Analysing the food chain (planktonic or detrital)

z

z Determining nutrient limitationDetermining nutrient limitation

z

z Performing mass balances, i.e. Understanding stocks Performing mass balances, i.e. Understanding stocks and fluxes

and fluxes

z

z Management of input and uptakeManagement of input and uptake

z

z Understanding the role of autochtonous production, Understanding the role of autochtonous production, external inputs and export (outwelling)

external inputs and export (outwelling)

z

(18)

OAERRE data + TICOR data

Chlorophyll

a

and nutrients

Maximum spring phytoplankton (chl aµg L-1₎

0 5 10 15 20 25 30 GF KF FC Ria Formosa HF GM Tejo Sado Mondego Mira*1 Guadiana Ria de Aveiro*2 50 60 70 80

Tett, P., Gilpin, L., Svendsen, H., Erlandsson, C.P., Larsson, U., Kratzer, S., Fouilland, E., Janzen, C., Lee, J., Grenz, C., Newton, A., Ferreira, J.G., Fernandes, T., Scory, S., 2002. Eutrophication and some European waters of restricted exchange. Submitted to Coastal and Nearshore Oceanography, NEEA, and unpublished work from TICOR.

Maximum winter DIN (µM)

0 10 20 30 40 90 100 110 120

*1_{– Chlorophyll determined from graphical data}