http://ecowin.org/aulas/mega/pce Ocean chemistry J. Gomes Ferreira - - PowerPoint PPT Presentation

Ocean chemistry Coastal and Estuarine Processes http://ecowin.org/aulas/mega/pce

• J. Gomes Ferreira

http://ecowin.org/ Universidade Nova de Lisboa

Lecture outline

• Light – the primary driver of life in the sea
• Dissolved oxygen – a key limiting factor
• Natural ‘pollution’ – the Black Sea
• Carbon in the ocean – the cycle, the consequences
• Shellfish and the carbon economy
• Nutrients – nitrogen and phosphorus
• The Redfield ratio, distributions, and models

Light, dissolved oxygen Coastal and Estuarine Processes http://ecowin.org/aulas/mega/pce

• J. Gomes Ferreira

http://ecowin.org/ Universidade Nova de Lisboa

Radiation units

Illumination, energy, power density...

Adapted from: Parsons, Takahashi & Hargrave, 1984. Biological Oceanographic Processes 3rd.

• Ed. & Jërlov - Light in the Sea

Unit Conversion to Type Meaning/comments lux (lx) 6 X 10-6 ly min-1 Light at sea surface lux (lx) 1 IC m-2 Flux (illumination/time) international candle (IC) Illumination langley 1 gcal cm-2 Energy/area Einstein (1 mol) 6.02 X 1023 quanta Energy Einstein 52000 gcal For l=550 nm gcal 4.185 Joule Energy mE m-2 s-1 Power density 500-1500 at sea surface W m-2 1 J s-1 m-2 Power density 200-600 at sea surface

Dissolved oxygen in seawater

Units and ranges

Dissolved oxygen is a critical limiting factor for life in seawater.

5 10 15 20 25 30 35 12.5 25 37.5 2 4 6 8 10 12 14 16 14-16 12-14 10-12 8-10 6-8 4-6 2-4 0-2 O2 (mgL-1) Salinity

 O2 is usually measured in mg L-1 or ml L-1  Dissolved oxygen in seawater ranges from 0-10 mg L-1  The atomic mass of O2 (32g) corresponds to 22.4 litres at STP, so 5 ml L-1 = 5 X 32/22.4 i.e. about 7 mg L-1  The maximum oxygen concentration in seawater (~ 7 ml L-1) is therefore about 30 times lower than in air (200/7)  The solubility of oxygen depends on the salinity and temperature of the water.

Sources and sinks of dissolved

• xygen in seawater

Oxygen is supplied in the mixed layer, deeper water is a net oxygen sink. Sources Sinks Mixing

Reaeration

Ocean Atmosphere

Depth z (m) Light (mmol m-2 s-1)

1% I0 I0

Compensation depth Photic zone Dysphotic zone Primary production Heterotrophic consumption Bacterial decomposition Advection & Diffusion

dI dz = - kI

PAR = 0.42 I

GIS – dissolved oxygen

Tagus Estuary

The estuary does not show significant oxygen problems.

Winter Summer

Surface Bottom

Summer D.O. (mg/l)

Surface Bottom

Winter D.O. (mg/l)

10 20 km

GIS – dissolved oxygen

Tagus Estuary - summer

In summer, the estuary does not show vertical stratification.

Surface Bottom Surface - Bottom

D.O. (mg/l) Surface - Bottom D.O. (mg/l)

10 20 km

GIS – dissolved oxygen

Tagus Estuary - winter

In winter, vertical stratification is more evident, with lower bottom water D.O.

Surface Bottom Surface - Bottom

D.O. (mg/l) Surface - Bottom D.O. (mg/l)

10 20 km

GIS – oxygen saturation

Tagus Estuary

Oxygen saturation in the estuary is generally above 70%.

Surface Bottom

Summer Oxygen Sat (%)

Surface Bottom

Winter Oxygen Sat (%)

10 20 km

Winter Summer

GIS – dissolved oxygen

Tagus Estuary - summer

There is no difference in oxygen saturation except in hotspots like the Sorraia.

Surface Bottom Surface - Bottom

Oxygen Sat (%) Surface - Bottom Oxygen Sat (%)

10 20 km

GIS – dissolved oxygen

Tagus Estuary - winter

The upper part of the estuary shows significant differences in winter.

Surface Bottom Surface - Bottom

Oxygen Sat (%) Surface - Bottom Oxygen Sat (%)

10 20 km

Dissolved oxygen in the maximum turbidity zone

Tagus estuary

There appears to be a clear sag in summer dissolved oxygen – is this pollution?

2 4 6 8 10 12 14 50 100 150 200 250 300 350 400

Julian day Dissolved oxygen (mg L-1) Oxygen sag

Dissolved oxygen and percentage saturation in the maximum turbidity zone

Tagus estuary

The effect of pollution seems to have disappeared.

Julian day Dissolved oxygen (mg L-1) 2 4 6 8 10 12 14 50 100 150 200 250 300 350 400

20 40 60 80 100 120 140 160

Percentage saturation O2 (%) % saturation D.O.

Case study- natural “pollution”

Hypoxia in the Black Sea

http://www.ancientrade.com/

Mediterranean Sea- Circulation

Two major deep basins, increasingly saline and oligotrophic.

40o N 45o N 5o W 0o W 5o E 10o E 15o E 20o E 25o E 30o E 35o E 1000m 2000m 3000m 4000m 28oC 20oC 12oC 4oC

Black Sea – Circulation Freshwater input from the NW coast

http://www.grid.unep.ch/

Name Catchment Length Total Total Sediment area runoff runoff discharge km2 km km3 y-1 m3 s-1 106 t y-1 Danube 817000 2860 208 6596 51.7 Dnieper 505810 2285 51.2 1624 2.12 Dniester 71990 1328 10.2 323 2.5 Southern Bug 68000 857 3 95 0.53 Chorokh 22000 500 8.69 276 15.13 Rioni 13300 228 12.8 406 7.08 Inguri 4060 221 4.63 147 2.78 Kodori 2030 84 4.08 129 1.01 Bzyb 1410

• 3.07

97 0.6 Yesilrmak

• 416

4.93 156 18 Kizilrmak

• 1151

5.02 159 16 Sakarya

• 790

6.38 202

• Total

1505600 8363 306 9693 83 Three major rivers, including the largest European river (runoff: 15X Tagus).

Black Sea – surface temperatures

High temperatures in the summer limit the oxygen concentration of the surface layer. http://www.grid.unep.ch/

http://daac.gsfc.nasa.gov Bosporus Danube estuary

Black Sea – Coccolith blooms (SeaWifs)

These turquoise-coloured blooms can account for 90% of the phytoplankton biomass.

Black Sea – circulation and stratification

High concentrations of sulphide in the anoxic bottom waters. http://daac.gsfc.nasa.gov/

Consequences

• Brackish, oxygenated mixed layer
• Saline, hypoxic deep water (same occurs in fjords)
• Elevated concentrations of sulphide in deep water
• Overturn events deplete dissolve oxygen from mixed layer

and cause fish kills

• Dead animals increase organic decomposition and

depletion of dissolved oxygen, a positive feedback cycle of pollution

• This is an example of natural “pollution”

http://insightmaker.com/insight/9381 Understand more about simulating dissolved oxygen using an online model:

Carbon Coastal and Estuarine Processes http://ecowin.org/aulas/mega/pce

• J. Gomes Ferreira

http://ecowin.org/ Universidade Nova de Lisboa

Distribution of carbon on the planet

Ocean holds 60X more carbon than the atmosphere. Most carbon is only mobile on a geological (not ecological) time scale.

Reservoir gC X 1020 Atmosphere (1973) 0.00675 Ocean Inorganic carbon 0.38 Organic carbon (live) 0.01 Detritus 0.0129 Land Organisms 0.0164 Organic C (sedimentary rock) 68.2 Calcareous rock 183

Carbon transport to the ocean

Phytoplankton is the elephant in the room.

Source gC y-1 X 1014 % Primary prod. (phytoplankton) 200 - 360 98.9 Rivers and streams 3 - 3.2 1.1 Groundwater 0.8 0.3 Aerosols, volatile compounds 1.5 - 4 0.6 From plants Hydrocarbons (oil) 0.046 0.017

After Handa (1977), Duce & Duursma (1977) & Farrington (1980) In Valiela, I., Marine Ecological Processes

Distribution of Particulate Organic Matter

Data from various authors, in Valiela, Marine Ecological Processes Much of the POM in the ocean is detritus, and we don’t know much about bacteria.

Particulate % total

• rganic

POM matter (ugC l-1) Phytoplankton Zooplankton Bacteria Detritus Sea of Azov 750-1500 5-10 3-10 0.3-7 80-92 Arabian Sea 100-250 1-31 Black Sea 200-250 0.2-1 5-20 0.4 78-95 Tropical Atlantic 15o meridian 450-600 0.5-1.3 0.6 98-99 16o parallel 100-250 0.6-1.3 0.7 98-99 Upwelling 70-900 30-43 4-14 9-14 (South Africa) Hudson estuary 660-2250 2-72 40-93 New York Bight 200-840 12-51 38-90 Baltic (western) 492-505 23-27 33-35 41-43 Chesapeake Bay 11.5-84 23 77 English Channel 950-2500 15-17 Aberdeen Bay 200-3400 8-10 Wadden Sea 1000-4000 10-25 Akeshi Bay 9.7 1.7

Extracelular enzymes

Carbon cycle in the marine environment

CO2 (gas) CO2 (dissolved) Consumers (animals) POC DOC

Respiration Grazing Grazing Losses Excretion Exudation Heterotrophy Heterotrophy Agreggation/adsorption Enzymatic decay Consumption Death Elimination Death Resuspension Marine snow carcasses Faeces & molts Photosynthesis Terrestrial sources (rivers, primary producers, precipitation, spills)

Land Atmosphere Ocean

Exudation 7-62% of carbon fixed (carbohydrates, aa’s, phenols, etc)

Primary producers Consumers (microorganisms)

Excretion 3-10% of photosynthetically fixed carbon Cell leakage 15-20% of carbon consumed Leaching 14-60% of intial weight

• f dead material

Carbon cycle in the marine environment

1000 2000 3000 4000 5000 6000 1.9 2.0 2.1 2.2 2.3 2.4 Total CO2 (nmol kg-1) North Atlantic North Pacific Depth(m)

Adapted from GEOSECS atlas - vols. 2 & 4

The biological carbon pump transports CO2 to the deep ocean. Higher concentrations in the Pacific reflect longer water residence time.

Sediment traps Different designs, same idea

http://jpac.whoi.edu/atsea/instrument.html http://smithlab.ucsd.edu/Antarctic/ http://www.fimr.fi/

Sediment traps

 Capture larger particles (faecal pellets, etc) which fall at a rate of hundreds of metres per day  Should not be placed too near the bottom (resuspension) or too near the surface (mixing)  May be scavenged by deep-sea

• rganisms

 “Inhibitors” may be added to reduce this effect

200 400 600 800 1000 1200 125 62 31 16 8 4 Fall velocity (m d-1) Particle diameter (mm)

Copepod fecal pellet Ø = 50-100 mm

 Isotopic markers may be used to identify particle sources, using fallout tracers and other approaches Marine snow is the mechanism which accounts for rapid transport of

• rganic material to the deep sea and benthos.

Relationship between cell diameter and sinking rate

Slope predicted by Stokes Law Senescent cells Growing cells

1.0 10 100 1000 Mean cell diameter (mm) Mean sinking rate (m d-1) 1.0 10 100

Smayda, T.J., 1970 - Oceanogr. Mar. Biol. Ann. Rev. 8, 353-414

0.1 Living cells sink slower than dead ones.

Vertical carbon flux in the northeast Pacific

Flux is highest in the mixed layer, where organic production occurs. 1000 500 1500 2000 2.0 3.0 mol C m-2 y-1) Depth(m) 1.0

Results from 6 stations, obtained through sediment traps. Martin et al., 1987, Deep Sea Res. 34, 267-285

Sedimentation of POC

Ecosystem POC flux from % primary % benthic surface waters production respiration (mgC m-2 d-1) (%) (%) Low productivity Equatorial Atlantic 6.8 0.8 (5000 m) 133-667 NW Atlantic 5.5-16.5 4-6 (~3000 m)

• Oligotrophic gyres

1.6 6.2

• High productivity

Peru upwelling 533 10 (50m)

• New York Bight

299 59

• Coastal waters

37-168 30-46

• Various authors, In Valiela, I., Marine Ecological Processes, 1984 - Springer-Verlag

Aquatic photosynthesis and sedimentation

• f organic carbon

Region Area (km2) Net primary Sediment organic production carbon sink (x1012 kgC yr-1) (x1012 kgC yr-1) Open ocean 3.1 X 108 18.6 0.19 Continental shelf 2.7 X 107 5.40 Continental slope 3.2 X 107 2.24 0.50 Fresh water marshes 1.6 X 106 1.51 0.15 Estuaries and deltas 1.4 X 106 0.92 0.20 Salt marshes 3.5 X 105 0.49 0.05 Rivers and lakes 2.0 X 106 0.40 0.13 Coral reefs 1.1 X 105 0.30 0.01 Seaweed beds 2.0 X 104 0.03 Total 3.75 X 108 29.89 (C input) 1.23 (C output) Walsh & Dieterle, 1988 - In Scales and Global Change, Wiley, New York

CO2 content and D in Vostok ice core 2200m deep - 160000 years before present (BP)

Ice for forensic analysis of CO2. Deuterium is a good temperature proxy. Present CO2 level Carbon dioxide Deuterium 40 80 120 160 500 480 460 440 420 360 320 280 240 200 Years before present (thousands) Deuterium D (ppm) CO2 (ppm)

• 5
• 10

Temperature change (oC)

Interglacial period (140000- 116000 years BP) End of last ice age (15000 years BP)

Barnola et al., 1987. Nature, 329:408-412

Vertical carbon flux in the northeast Pacific

Models of this kind are useful but have great uncertainties. Stocks in Gt C Fluxes in Gt C y-1

Land biota 639 ± 186 1625 ± 637 Soil

Atmosphere

747 (=355 ppm) (annual change: +3.4 ± 0.2 ppm) DIC 0.45 DOC 0.2-0.5 POC 0.1-0.3 32.3 ± 11.8 Plankton 1.7 ± 1.9 Logging Oil Erosion 5.3 ± 0.5 0.3 ± 0.3 0.3 - 11.0 54.3 ± 9.5 80 ± 23 Net: 1.5-2.5

Surface layer

DIC 1000 DOC ??? 25.3-27.3 DIC 37 DOC ?? POC 7- 9 PIC 0.75 ± 0.3

Pycnocline Intermediate and deep water

DIC 36700 POC 4.7 DOC 1198 POC 0.04 PIC 0.15 Sediments POC 6000000 PIC 14000000

Options for ocean productivity

Plankton (warm water) 20 2.0 f = 0.1 Plankton

(cold water)

10 5.0 f = 0.5 Plankton (warm water) 20 6.0 f = 0.3 Plankton

(cold water)

10 3.0 f = 0.3 River flux

Sequestration of carbon by shellfish

• The carbon removed by consumption of algae and detritus is an effective

carbon sink, since the organic material removed is not mineralised in the water

• The carbon used for building the calcium carbonate (CaCO3) shell is not a net

sink

• Formation of CaCO3 removes CO2 but also removes calcium, thereby

changing the alkalinity of seawater removal: Ca2+ + HCO3

• CaCO3 + H+
• As a consequence, the pH buffer system in seawater increases the

dissociation of bicarbonate: H+ + HCO3

• CO2 + H2O
• The net effect is zero change in marine CO2 as a result of shell building, so

there is no drawdown from the atmosphere Shell formation in bivalves is not a carbon sequestration mechanism. Effect on greenhouse gases What is the role of shellfish?

Nutrients Coastal and Estuarine Processes http://ecowin.org/aulas/mega/pce

• J. Gomes Ferreira

http://ecowin.org/ Universidade Nova de Lisboa

Nitrogen cycle in the marine environment

Producers & bacteria Dissolved N2 NH4 DIN Land NH3 Particulate nitrogen Sediments

Guano, fisheries

Atmospheric nitrogen DON NO3 Fixed NH4 DON Non-living Part-N

Denitrification Death Regeneration Decomp. Excretion Regeneration Adsorption Ionic exchange Nitrification Ammonification Denitrification Decomp. Decomp. Absorption Uptake Fixation Grazing Sedimentation Freshwater, rain, sewage Volatilization Hetero.

Consumers

Land Atmosphere Ocean

Phosphorus cycle in the marine environment

Algae and plants DOP Bacteria DIP POP

Pastagem Exudation Heterotrophy Death Moults, excretion, and death

Terrestrial sediments Man Seabirds Animals

Decomposition Feeding

Insoluble P compounds Sediments

Sedimentation Guano Fishing Hydrolysis Dissolution Adsorption Precipitation Uptake Autolysis Uptake Regeneration Fluvial and wind transport Agriculture, sewage Mining

Land Atmosphere Ocean

Transformations of nitrogen

Organic nitrogen

Excretion Decomposition Uptake Uptake and assimilative reduction in cells Dissimilative reduction Nitrification Nitrification

N2 fixation

NH4

+

Ammonium NH2OH Hiyroxylamine NO2

• Nitrite

NO Nitric

• xide

NO3

• Nitrate

N2O Nitrous

• xide

N2 N gas Oxidation state

• 3
• 1

1 2 3 5

Fenchel & Blackburn, 1979. Bacteria and mineral cycling. Academic Press.

GIS – annual mean DIN in the Tagus Estuary

There is a clear gradient in the dissolved inorganic nitrogen concentration.

DIN (umol l-1) Limit of salt intrusion Lisboa Atlantic

• cean

10 20 km

NO3-Temperature relationship for the eastern tropical Pacific (Aug.-Nov. 86-88)

Nitrate concentration increases with depth.

Nitrate mM Temperature oC 10 20 30 40 50 n = 5035 10 20 15 25 30 5 35

Fiedler et al., 1991 - Limnol. & Oceanog. 36, p. 1834-50

Redfield Ratio

Definitions

 “Standard” ratio of C:N:P  May be expressed in atoms or mass  Derives from the constancy of composition of biota  C:N:P 106:16:1 (in atoms)  C:N:P 45:7:1 (in mass)  Oxygen may also be included, considering that for every carbon atom fixed two oxygen atoms are produced

CO2 + 2H2A CH2O + 2A + H2O

Light Pigments

O:C:N:P 212:106:16:1

PO4 - NO3 relationship for the eastern tropical Pacific (Aug.-Nov. 1986-88)

Redfield ratio of about 15:1 (N:P). Fiedler et al., 1991 - Limnol. & Oceanog. 36, p. 1834-50

Phosphate mM 1 2 3 4 10 20 30 40 Nitrate mM 50 n = 5338

SiO4 - NO3 relationship for the eastern tropical Pacific (Aug.-Nov. 1986-88)

The ratio of silica to nitrate can vary substantially. Fiedler et al., 1991 - Limnol. & Oceanog. 36, p. 1834-50

20 40 60 Silicate mM 10 20 30 40 Nitrate mM 50 n = 5324

N:P ratio for the Tagus Estuary

The Tagus estuary is nitrogen limited.

10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 6 7 8 9 10

PO4

3- (mmol L-1)

n=1841 45 stations ~20 years DIN (mmol L-1)

N:P ratio for Carlingford Lough, Ireland

Carlingford Lough does not seem to have a clear nutrient limitation pattern.

20 40 60 80 100 120 1 2 3 4 5

PO4

3- (mmol L-1)

n=859 73 stations 4 years (1990-1993) DIN (mmol L-1)

N:P ratio for Carlingford Lough, Ireland

seasonal analysis

Carlingford Lough is P limited in winter and N limited in summer.

Julian day n=859 73 stations 4 years (1990-1993) N/P ratio (no units)

2 4 6 8 10 12 14 16 18 20 50 100 150 200 250 300 350 400

Strong N limitation

GIS – annual mean DIP in the Tagus Estuary

There is a clear gradient in the phosphate concentration.

DIP (umol L-1) Limit of salt intrusion Lisboa Atlantic

• cean

10 20 km

GIS – mean Redfield ratio in the Tagus Estuary

The Tagus estuary is nitrogen limited.

N/P (mol ratio) Limit of salt intrusion Lisboa Atlantic

• cean

10 20 km

Redfield Ratio - Applications

Applications

 Analysing the food chain (planktonic or detrital)  Determining nutrient limitation  Performing mass balances, i.e. understanding stocks and fluxes  Management of input and uptake  Understanding the role of autochtonous production, external inputs and export (outwelling)  Ecological modelling (currency tables)

Caveat

A mean ratio, in some cases the variance will be large!

OAERRE data + TICOR data Chlorophyll a and nutrients

No universal relationship emerges between chlorophyll and DIN.

Maximum spring phytoplankton (chl a mg L-1) Maximum winter DIN (mM)

5 10 15 20 25 30 10 20 30 40

GF KF FC Ria Formosa HF GM

50 60 70 80

Tejo Sado

90

Mondego Mira*1

100 110 120

Guadiana Ria de Aveiro*2

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. Continental Shelf Research, 23, 1635-1671, NEEA, and TICOR - Typology and Reference Conditions for

Portuguese Transitional and Coastal Waters. INAG/IMAR, 2003.

*1 – Chlorophyll determined from graphical data *2 – Nitrate, not DIN

Mass balance for loading and regeneration of nutrients in Narragansett Bay, U.S.A.

Mass balance analysis helps to understand mass and energy flow in ecosystems.

Annual input (106 g-at y-1) Nitrogen Phosphorus Inputs Fixation 0.2

• Precipitation

2.8 0.19 Runoff 16.2 0.8 Rivers 235 17.3 Sewage 278 21.7

• Total

532 39.9

Regeneration Menhaden 0.8 0.1 Ctenophora 8.1 0.8 Zooplankton 98.5

• Benthos

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.

Nitrogen mass balance for Sippewissett marsh, U.S.A. All values in kg N y-1.

Mass balance analysis highlights the importance of physical processes. Inputs Outputs Net exchange Precipitation 380 380 Groundwater 6120 6120 N2 fixation 3280 3280 Tidal exchange 26200 31600

• 5350

Denitrification 6940

• 6940

Sedimentation 1295

• 1295

Others 9 26

• 17
• Total

35990 39860

• 3870

% biotic exchange 9 18 % physical exchange 91 82

Valiela & Teal (1979). The nitrogen budget of a salt marsh ecosystem, Nature 280, 652-656. Minus signs indicate export from the saltmarsh

DIN mass balance for Cala do Norte (kg N y-1)

Primary production removes almost 10% of the nutrient input.

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

Advection-dispersion Internal processes Total 38 kg y-1 (approx. zero) N

• 0.113 mat g DIN L-1 y-1

Phytoplankton N mass balance for Cala do Norte (gN m-2 y-1)

Normalization per unit area allows a comparison among ecosystems.

Inputs Upstream 11.88 Sub-total 11.88 Outputs Downstream

• 28.24

Sub-total

• 28.24

Total

• 16.36

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

Advection-dispersion Internal processes

Total 0 g m-2 y-1 Stock 0.150 gN m-2

Simulation of dissolved oxygen with IMTA

Top-down control of eutrophication symptoms short-circuits organic decomposition

Phase 3 & 4 TMDL: N & Corg With shellfish and seaweeds

Change in dissolved oxygen through the use of IMTA

System-Wide Eutrophication model (SWEM) HydroQual, 2009. Model year simulation: 1988

4.0 3.0 2.0 1.0 0.0 +4.0 +2.0 0.0

• 2.0
• 4.0

Minimum D.O (mg L-1)

Long Island Sound oyster farm

FARM model simulation for nutrient trading

Oyster cultivation in this 50 acre farm provides an ecosystem service equivalent to removal of nutrient discharge by over 300 people.

Shellfish aquaculture and the global nitrogen budget (upscaled from FARM results)

Waste nitrogen 22.1 million t y-1 Mollusc aquaculture 12 million t TFW y-1 Net uptake of algae and detritus 661,000 t N y-1 World population 6.7 billion people 3.3 kg N y-1 3%

97%

1.8 kg y-1

Per capita equivalent Everyone in the world eats one mussel daily

Substantial ecosystem services (53 billion € y-1, 2% UK GDP) 4.9 g d-1

Synthesis

• The availability of light and oxygen conditions the overall

functioning of marine systems

• The sea is the most important reservoir of CO2 on the

planet, and plays a major part in climate regulation

• Organic cycles are an image of life. There are important

differences between N and P cycles, particularly with respect to the sediment component

• Nutrient

ratios and distributions are critical to understanding organic production and water management

http://ecowin.org/aulas/mega/pce

All slides