Marine Ecosystems and Food Webs
description
Transcript of Marine Ecosystems and Food Webs
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Marine Ecosystems and Food Webs
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Carbon Cycle
Marine Biota
Export Production
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Export Production of Organic Carbon
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Trophic levels and dynamics
Ocean Ecosystem Structure
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Trophic levels and dynamics
Ocean Ecosystem Structure
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Trophic levels and dynamics
Ocean Ecosystem Structure
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Trophic levels and dynamics
Ocean Ecosystem Structure
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Example of a more complex Food Web
Ocean Ecosystem Structure
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Energy Transfer between Trophic Levels is not efficient
Ocean Ecosystem Structure
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Trophic levels and dynamics
Food Web
Energy
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ENERGY
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How about Mass Transfer?
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How do we measure Biomass?
Mass transfers are more easy to keep track than energy transfers
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Alaska
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200 km
Large scale Eddies
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• Color sensor satellites: MODIS, SeaWiFS, MERIS, OCTS, and CZCS http://oceancolor.gsfc.nasa.gov/SeaWiFS
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A simplified diagram of an ecosystem
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A useful way to keep track of biomass in the lower trophic levels is to follow the path of MACRONUTRIENTS
Carbon C Nitrogen N
Phosphorus P
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Redfield Ratio
C : N : P106 : 16 : 1
Redfield A.C., 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, 1934. This works stems from his participation as a physiologist in the voyages of WHOI's first research vessel Atlantis.
Atlantis in 1934and today
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source 1) atmosphere
source 1) not biological, not atmospheric2) fluvial
C : N : P
source 1) from N2 atmosphere gas2) ocean subsurface3) remineralization of dead organic matter4) biological (e.g. excretions)
At large Nitrogen appears to be the limiting factorin ocean productivity in today’s oceans
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What is the explanation for the Redfield ratio?
• Redfield (1958) “biological control of chemical factors" in the ocean: living organisms in the ocean evolved to have a N:P ratios of about 16 → when N is not limiting then N and P but also C and O interact to produce this relation.
• Very stable in deep ocean • Not so stable between phytoplankton species.
• Perhaps only general average?
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N
D
P
Z
h
S(No-N) n
NP
k N
DD zZZ
Pg
Pg2
2
Pp
h
Dws
2Zz
2
2(1 )
g PZ
g P
Simple Nitrogen ModelN=nitrogenP=phytoplank.Z=zooplank.D=detritus
~1 Pg C(0.2 % of photosynthetic biomass)
NPP
Net Primary Production (NPP) ~45 Pg C/yr
Phytoplankton biomass turns over in about a week!
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NO3
Chlorophyll
Largedetritus
Organic matter
N2 NH4 NO3
Water column
SedimentSediment
Phytoplankton
NH4
Mineralization
Uptake
Nitrification
Nitrification
Grazing
Mortality
Zooplankton
Susp.particles
Aerobic mineralizationAerobic mineralizationDenitrificationDenitrification
N2
Fixation
Mix Layer depth
Description of the oceanic ecosystem based on Nitrogen exchanges
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Carbon Cycle
Marine Biota 45 GIC/yr
Export Production
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What are the controls on Primary Production?
Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients
Ocean nutrient inventory
Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions)
Changes in Redfield Ratio
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Export Production of Organic Carbon
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Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients
Ocean nutrient inventory
Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions)
Changes in Redfield Ratio
What are the controls on Primary Production?
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Nutrient Sources for Primary Production
The flux of organic carbon must be sustained by an adequate flux of macronutrients
If macronutrients are unavailable then primary production is reduced!
What are the controls on Primary Production?
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Surface CHL-A
1) Central Gyres 2) Upwelling Regions
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Phytoplankton Blooms and Physical Environment
Bands of the dionflagellate Lingulodinium polyedrum moving onshore over the troughs of a series of internal waves
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Nonlinear Internal Waves and Phytoplankton
Isopycnals
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Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients
Ocean nutrient inventory
Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions)
Changes in Redfield Ratio
What are the controls on Primary Production?
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Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients
Ocean nutrient inventory
Nitrogen appears to be the limiting factor for growth in modern time.
C : N : P106 : 16 : 1
What are the controls on Primary Production?
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N* = N – 16 P (Gruber & Sarmiento 1997)N* = N – 16 P (Gruber & Sarmiento 1997)
N = 25790
NN22 fixation fixation
DenitrificationDenitrification
Modern TIME
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Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients
Ocean nutrient inventory
Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions)
Changes in Redfield Ratio
What are the controls on Primary Production?
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Southern Ocean HNLC
Map of annual average nitrate concentrations in the surface waters of the oceans. Data from
Levitus, World Ocean Atlas, 1994.
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Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients
Ocean nutrient inventory
Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions)
Changes in Redfield Ratio
What are the controls on Primary Production?
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Ocean Circulation (e.g. gyres, coastal upwelling, eddy fluxes) modulates the fluxes of essential nutrients
Ocean nutrient inventory
Utilization of nutrients in HNLC (High Nutrients Low Chlorophyll regions)
Changes in Redfield Ratio
What are the controls on Primary Production?
Climate
Variabilit
y and Change