marine productivity_mest 2013

7/29/2019 Marine Productivity_MEST 2013

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Marine Product iv i ty

By Dr. Nita Rukminasari


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Outlined Lectured

Productivity vs biomass

Food chain

Food web and trophic dynamic

Transfer energy between trophic level

Ocean food web

Primary productivity

Regional productivity Measuring primary productivity

Geographic variation of productivity


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Product iv i ty vs biomass

Biomass the mass of living material

present at any time, expressed as gramsper unit area or volume

Productivity is the rateof production ofliving material per unit time per unit area

or volume


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Product iv i ty

Primary productivity - productivity due to

Photosynthesis

Secondary productivity - productivity due t

consumers of primary producers


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Food Chain

Food chain - linear sequence showing

which organisms consume which otherorganisms, making a series oftrophic lev

Food web - more complex diagram showifeeding relationships among organisms, n

restricted to a linear hierarchy


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Food Chain Abstract ion

Adult

herring

Phytoplankton

Barnaclelarvae

Mollusk

larvae Smallcopepods

euphausid tunicate

cladocerans

amphipodsand eel

Young herring

arrowworm

Larger

copepod

Phytoplankton

Copepod

Herring

Food chain Food Web


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The word

trophic

refers tonutrition. Trophic dynamics is the study of the nutritional

interconnections among organisms within an ecosystem.

Trophic level is the position of an organism within the trophicdynamics.

Autotrophs form the first trophic level.

Herbivores are the second trophic level.

Carnivores occupy the third and higher trophic levels.

Decomposers form the terminal level.

A food chain is the succession of organisms within an

ecosystem based upon trophic dynamics. (Who is eaten by

whom.)

Food Webs and Trophic Dynamics


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Trans fer Between Troph ic

LevelsTransfer from one trophic level to the

next is not complete:

1. Some material not eaten

2. Not all eaten is converted with 100%

efficiency


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Levels2Budget for ingested food (use energy units

I = E + R + G

I amount ingested

E amount egestedR amount respired

G growth (partitioned between somatic

growth and reproduction)


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Levels3Incomplete transfer up a food chain:

Measure by food chain efficiency:

E = amount extracted from a trophic level

amount of energy supplied to that leveOften in range of as little as 10%


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Levels4Use food chain efficiency to calculate

energy available to highest trophic level:

P = BEn

B = primary productionP= production at highest level

E= food chain efficiency

N= number of links between trophic levels


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P = BEn

Let E = .1, B = 1, n = 2,3,4If n = 2, P = ?


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P = BEn

Let E = .1, B = 1, n = 2,3,4If n = 2, P = ?

P = 1 x (0.1)2 = 1 x 0.01 = 0.01


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P = BEn

Let E = .1, B = 1, n = 2,3,4If n = 3, P = ?

P = 1 x (0.1)3 = 1 x 0.1 x 0.1 x 0.1 = 0.001


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P = BEn

With 5 trophic levels, a change ofEfrom0.1 to 0.2 magnifies Pby a factor of 16


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Ocean ic Food Webs

Food webs in the oceans vary

systematically in food chain efficiency,

number of trophic levels, primary

production


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Ocean ic Food Webs

Food

Chain

Type

Primary

Productivit

y

gCm-2y-1

Trophic

Levels

Food

Chain

Efficiency

Potential

Fish

Production

mgCm-2y-1

Oceanic 50 5 10 0.5

Shelf 100 3 15 340

Upwelling 300 1.2 20 36,000


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Ocean ic Food Webs

Food

Chain

Type

Primary

Productivit

y

gCm-2y-1

Trophic

Levels

Food

Chain

Efficiency

Potential

Fish

Production

mgCm-2y-1

Oceanic 50 5 10 0.5

Shelf 100 3 15 340

Upwelling 300 1.2 20 36,000


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Ocean ic Food Webs

Food

Chain

Type

Primary

Productivit

y

gCm-2y-1

Trophic

Levels

Food

Chain

Efficiency

Potential

Fish

Production

mgCm-2y-1

Oceanic 50 5 10 0.5

Shelf 100 3 15 340

Upwelling 300 1.2 20 36,000


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Ocean ic Food Webs

Food

Chain

Type

Primary

Productivit

y

gCm-2y-1

Trophic

Levels

Food

Chain

Efficiency

Potential

Fish

Production

mgCm-2y-1

Oceanic 50 5 10 0.5

Shelf 100 3 15 340

Upwelling 300 1.2 20 36,000


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Ocean ic Food Webs

Note: Great potential of upwelling areas

due to combination of high primary production,

higher food chain efficiency, lower numberof trophic levels


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Ocean ic Food Webs

Stable, low nutrient Turbulent, hi h nutrient

Few trophic

levels

Many

trophic

levels

Open ocean,gyre centers

Shelf,upwelling


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Primary productivity

Primary productivity is the amount of

carbon (organic matter) produced by

organisms Mostly through photosynthesis

Energy source = solar radiation

Also includes chemosynthesis Energy source = chemical reactions


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Photosynthetic productivity

Figure 13-1


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Oceanic photosynthetic

productivity Controlling factors affecting

photosynthetic productivity:

Availability of nutrients Nitrates

Phosphates

Iron

Amount of sunlight Varies daily and seasonally

Sunlight strong enough to supportphotosynthesis occurs only to a depth of 100meters (euphotic zone)


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Locations of maximum

photosynthetic productivity Margins of the oceans

Abundant supply of nutrients from land

Water shallow enough for light to penetrateall the way to the sea floor

Upwelling areas

Currents hoist cool, nutrient-rich deepwater to the sunlit surface


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Coastal upwelling

Figure 13-3


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The electromagnetic spectrum

and light penetration inseawater

Figure 13-4


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Water color and life in the

ocean Ocean color is influenced by:

The amount of turbidity from runoff

The amount of photosynthetic pigment, whichcorresponds to the amount of productivity

Yellow-green = highly productive water

Found in coastal and upwelling areas(eutrophic)

Clear indigo blue = low productivity water

Found in the tropics and open ocean(oligotrophic)


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Satellite view of world

productivity

Figure 13-6


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Photosynthetic marine

organisms: Plants Seed-bearing

plants

Eelgrass

(Zostera)

Surf grass

(Phyllospadix)

Figure 13-7

Surf grass


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organisms: Macroscopic algae Brown algae

Sargassum (top left)

Macrocystis (topright)

Green algae

Codium (bottom left)

Red algae

Lithothamnion

(bottom right)Figure 13-8


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organisms: Microscopic algae Microscopic algae include:

Golden algae Diatoms (silica test resembles a pillbox)

Coccolithophores (calcite plates form a sphericaltest)

Dinoflagellates

Produce a test made of keratin

Posses a whip-like flagella

Bioluminescence

Exist in great abundance, creating red tides

(harmful algae blooms)


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Dinoflagellates and red tides

Figure 13C


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Regional productivity

Photosynthetic productivity varies dueto:

Amount of sunlight

Availability of nutrients Thermocline (a layer of rapidly changing

temperature) limits nutrient supply

Examine three open ocean regions:

1. Polar oceans (>60 latitude)

2. Tropical oceans (


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Productivity in polar oceans

Sunlight peaks in

summer

Nutrients available

nearly year-round

(only weak

seasonalthermocline

develops)

Productivity:

Peaks in spring

Figure 13-10a


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Productivity in tropical oceans

Sunlight strongyear-round

Nutrients limitedby strong,permanentthermocline

Productivity: Steady, low rate

Limited bynutrients

Exceptions:

Figure 13-11


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Productivity in temperate

oceans Sunlight varies

seasonally

Nutrientslimited bythermocline

Productivity:

Spring bloomlimited bynutrients

Fall bloom

limited bysunlight Figure 13-12


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Productivity in tropical,

temperate, and polar oceans

Figure 13-13


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Measu r ing Primary

Product iv i ty

Gross primary productivity - total carbon fix

during photosynthesis

Net primary productivity - total carbon fixed

during photosynthesis minus that part whicis respired.


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Measu ring Primary

Product iv i ty2

Net Primary productivity most interesting:

gives that part of the production available tohigher trophic levels


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Measu ring Primary

Product iv i ty3Oxygen technique -

Principle - relies upon fact that

oxygen is released during photosynthesis

CO2 + 2H2O ---> (CH2O)n + H2O + O2


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Measu ring Primary

Product iv i ty4Oxygen technique 2 - there is an addition frphotosynthesis and a subtraction from

respiration


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Measu ring Primary

Product iv i ty5Oxygen technique 3 -

Measurement of oxygen:

Winkler technique - chemical titration of

Oxygen

Polarographic oxygen electrode -


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Measu ring Primary


Light-Dark bottle technique:

Light bottle gives oxygen from photosynth

minus oxygen consumed in respiration

Dark bottle gives oxygen consumed from

Respiration


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Measu ring Primary


Light-Dark bottle technique:

Start light and dark bottles with water sample,

a short amount of time

At end of experiment: oxygen in light minus th

dark bottle gives you gross photosynthesis

Measuring Primary Production:


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Measuring Primary Production:

light/dark bottle technique

Take water samples at different depths.

Place one subsample in a transparent (light)

bottle, another in an opaque (dark) bottle.

Resubmerge bottles to original depth. Retrieve after a similar, specified time

(hours)

Measure oxygen, in both Dark bottle: respiratory oxygen consumption

(should be same in both bottles).

Difference in oxygen conc between bottles:

Oxygen technique - effect of depth


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Oxygen technique effect of depth


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Measuring Primary Production Cont.

Problem: if zooplankton present, they will

consume oxygen, even in dark bottle (they arenot primary producers).

Other method: inject water samples with

radioactively-labeled bicarbonate (has C14

). After incubation period, filter phytoplankton

onto filter and measure radioactivity.

Method is very sensitive, measures CO2

takenup; problem: because it is so sensitive, therecan be a high margin of error.


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Measuring Primary Productivity-Cont.

Radiocarbon technique

Principle: carbon is taken up by cells During

photosynthesis, so if you label that carbon you

can trace it as it is incorporated into cells duringphotosynthesis.

Method: add bicarbonate to solution With

phytoplankton that is labeled with 14C

Incubate phytoplankton in the radiocarbon SolutionThen filter phytoplankton and count radiocarbon

Taken up by phytoplankton, using a scintillation

counter

Radiocarbon technique Cont


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Radiocarbon technique Cont.

Calculation:

1. Know the amount of bicarbonate that was in

container2. Know the amount of radiolabeled bicarbonate you

added and the amount that was taken up by

Phytoplankton allows calculation of amount ofbicarbonate taken up in photosynthesis

Correction:14C is taken up more slowly than much more common

stable isotope 12C. Therefore, need to multiplyresults by 1.05 to get amount in photosynthesis

What you get with this measure: Carbon

incorporation into phytoplankton (net

photosynthesis)


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Compare Oxygen technique

with radiocarbon Oxygen technique - used where primaryproduction is high in estuaries, shelf

Radiocarbon technique - useful where primary

production is low such as open ocean

Oxygen technique tends to give higher

estimates of primary production, perhaps

because cells are leaking sugars duringphotosynthesis, resulting in loss of

radiocarbon when cells are filtered and

counted


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Other Methods: Chl a

Chlorophyll a measurements.

Chl a concentration only roughly approximates

primary productivity.

Better used as an indicator of standing crop (i.e., you

are measuring a population, not an activity, not allthe population is involved in the activity).

If your population doesnt change, does that mean no

primary production is occurring? Nope

Balanced turnover rate: rate at which new

production replaces that lost to grazing, settling, etc.

(typically rapid: daily doubling).


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Satellite Approaches:

Satellites can use photometers specific

to

wavelength to measure

chlorophyll,Seawater temperature

Need ground truthing to get relationship

Between chlorophyll concentration and

primary production; varies with region


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sun

Satellite

ColorscannerIrradiance

Radiance

Phytoplankton

Ship based vs Satellite Sampling


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Ship-based vs. Satellite Sampling

Obviously, you miss a lot between widely-

based sampling stations.

Scientists resorted to averaging between

stations and periods: oops!

A lot was missed or lost. Problem solved by remote satellite sensing

using a coastal zone color scanner

(black/white converted to color, color represents level of phytoplankton standing

crops).

Calibrated via ship-based measurements.


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Geographic Variat ion o f

Product iv i ty1. Continental shelf and open-ocean upwelli

Areas are most productive

2. Convergences and fronts often are sitesrise of nutrient rich deep waters (e.g., shallo

water seaward of slope

3. Central ocean, gyre centers are nutrient plow primary production


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South

Pacific

North

Pacific

North

Atlantic

South

Atlantic

Antarctic

IndianOcean


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Satellite image of world productivity, from SeaWiFS satellite

Major Factors Affecting Primary


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Major Factors Affecting Primary

Productivity

Depends on both abiotic and biotic factors/

conditions.

Phytoplankton standing crop would increase

exponentially if nothing was limited.

Populations regulated by tolerance to

limiting factors.

Major ones: light, nutrient availability,

grazing by consumers.

Each major group responds differently to a

different set of conditions.


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Factors Affecting Primary

Productivity

Solar radiation

Uppermost surface seawater and shallow

seafloor Compensation depth net photosynthesis

becomes zero

Euphotic zonefrom surface to about

100 meters (330 feet)


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Light Transmission in Ocean

Water Visible light of the electromagnetic

spectrum

Blue wavelengths penetrate deepest Longer wavelengths (red, orange)

absorbed first


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Transmission of Light in

Seawater

Color in the Ocean


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Color in the Ocean

Color of oceanranges from deepblue to yellow-green

Factors

Turbidity from runoff Photosynthetic

pigment (chlorophyll) Eutrophic

Oligotrophic

Secchi Disk measureswater transparency

Upwelling and Nutrient Supply


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Cooler, deeper

seawater is nutrient-rich.

Areas of coastal

upwelling are sitesof high productivity.


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Thank you

marine productivity_mest 2013

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