Phytoplankton bloom – there is no officially recognized threshold level –range from 10,000s – 1,000,000s of cells per ml.

• Phytoplankton bloom– there is no officially recognized threshold level– range from 10,000s – 1,000,000s of cells per ml

Primary Production: Definitions and P vs. I

OutlineReview LightBeer’s LawPigments

PhotoadaptationPhotosynthesis

Primary ProductivityP vs. I Curves

More Aquatic Habitats (Vertical)

Continental Shelf

Continental S

lope

Abyss … Trench

1% Light Depth

Neritic OceanicCoastal

Euphotic zone

Permanent Thermocline

Bathypelagic

mesopelagic

EPIpelagic25m

100m

1000m

200m

Abyssopelagic

Not shown:

Seasonal Thermocline (varies, 10 – 400 m, depending on season and location)

What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light

Absorbed PAR

What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light

Absorbed PAR

• Scattered back out into the atmosphere

Can be detected by sensors in air or orbit

What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light

Absorbed PAR

• Scattered back out into the atmosphere

Can be detected by sensors in air or orbit

• Absorbed by waterHeats it up

What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light

Absorbed PAR

• Scattered back out into the atmosphere

Can be detected by sensors in air or orbit

• Absorbed by waterHeats it up

• Absorbed by plant pigmentsPhotosynthesis

What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light

Absorbed PAR

• Scattered back out into the atmosphere Can be detected by sensors in air or orbit

• Absorbed by waterHeats it up

• Absorbed by plant pigmentsPhotosynthesis

• Absorbed by dissolved materialsPhotochemistry

• Attenuation = a decrease in the energy of light due to absorption and scattering in the water column

• Attenuation coefficient (K) = describes the exponential decay of light with depth within the water column

Irradiance in the OceanIrradiance in the Ocean

Iz = irradiance at depth z

I0 = irradiance at surface

k = attenuation coefficient (m-1) (k also called absorption or extinction coefficient)

Iz = I0 e-kz

Beers LawI

z

Phytoplankton Pigments

• Pigments

Organic compounds (or organometals) that absorb light.

• Pigment – protein (complexes)

Include chromophores (pigment molecules) bound covalently to protein structures.

Roles of Pigments

• Absorb light energy for photosynthesis(Light Harvesting)

• Intercept or dissipate harmful light energy(Photoprotection)

• Convert light energy into chemical energy(Photochemistry)

Classes of Pigments in Marine Plants • Chlorophylls

• Carotenoids

• Biliproteins

Pigment analysisPigment analysisFluorometer

Shine blue light Fluoresces red

Chromatography

HPLC machine

Classes of Pigments in Marine Plants • Chlorophylls - Porphoryn rings, magnesium in

center (light harvesting and photochemistry)– Chl a– Chl b – Chl c

Classes of Pigments in Marine Plants • Chlorophylls - Porphoryn rings, magnesium in center

(light harvesting and photochemistry)– Chl a– Chl b – Chl c

• Carotenoids – carotenes simple chains of carbon and hydrogen (photoprotection)– Xanthophylls 400-500 nm gives brown color to marine plants– Beta-carotene does not feed energy in but absorbs light for

plants (sunscreen) protects phototrap from receiving too many electrons

– Fucoxanthin 510-525 nm give diatoms brown, olive-green color

Classes of Pigments in Marine Plants • Chlorophylls - Porphoryn rings, magnesium in center (light harvesting and

photochemistry)– Chl a– Chl b – Chl c

• Carotenoids – carotenes simple chains of carbon and hydrogen (photoprotection)– Xanthophylls 400-500 nm gives brown color to marine plants– Beta-carotene does not feed energy in but absorbs light for plants

(sunscreen) protects phototrap from receiving too many electrons– Fucoxanthin 510-525 nm give diatoms brown, olive-green color

• Biliproteins water soluble accessory pigments (reds, blues, purples) (photosynthetic light harvesting only)– Phycoerythrin 500-570 nm, Phycocyanin 550-650 nm

(red orange)

Absorption of light by Phytoplankton Absorption of light by Phytoplankton PigmentsPigments

400

500

600

700

Visible(PAR)

Absorption Spectra

Photoadaptation

• phytoplankton manufacture more chlorophyll – Increase umbrella to catch more of the sun's rays

• phytoplankton manufacture accessory pigments– expand the color range over which light can be

captured

• phytoplankton manufacture a set of pigments called protective pigments (carotenoids)– prevent intense sunlight from damaging the

photosynthetic apparatus, wide absorption bands that capture light energy and turn it into heat = photoinhibition

Antenna

• Complicated array of accessory pigments

(carotenes, xanthophylls, phycobilins)

Why do we care about pigments?

Some planktonic algae have large amounts of accessory pigments as well as Chl. What would the benefit be to that cost?

Biogeochemical Perspective on Biological Oceanography

• Rate Processes: Chemical transformations in the environment

Primary productivity (Photosynthesis and Respiration)

Remineralization

• Concept: Control of rate processes

• Concept: Limitation of rate processes

Primary Production (PP)

• The amount of autotrophic biomass produced per unit area (or vol) per unit time.

PP P – R

PP rate is independent of biomass eaten by grazers, lost to sinking, etc.

range from 1-5 g C/ m-2/ year-1 (central gyres)

to 200-400 g C/ m-2/ year-1 (upwelling areas)

1 m

1 m

Biomass (B) - The amount of living matter per area or volumeg C m-2, mg Chl a m-3

1 m

Photosynthesis

• Photosynthesis

6CO2 + 6H2 O → C6H12O6 + 6 O2

LIGHT & pigmentsLIGHT & pigments

• Respiration

6CO2 + 6H2 O ← C6H12O6 + 6 O2

Photosynthesis• Photosynthesis

6CO2 + 6H2 O → C6H12O6 + 6 O2

• Respiration

6CO2 + 6H2 O ← C6H12O6 + 6 O2

• Expressed as the RATE per VOLUME of the BIOMASS produced (mg C m-3 h-1)

the BIOMASS-SPECIFIC rate: (mg C mg Chl a-1 h-1) <- Assimilation Number

Photosynthesis can be expressed as:• Amount of carbon fixed OR • Amount of oxygen released

IMPORTANT NOTE: Photosynthesis is not equal to Primary Production

Example: Organisms also do RESPIRATION (R)

CH2O + O2 → CO2 + H2O + Energy

• Gross Primary Productivity (Pg)

– Total PP

• Net Primary Productivity (Pn)

– Gross PP – plant respiration

• Primary Productivity (PP) rate

• Respiration (R) rate

• Photosynthesis (P) rate

= mass/area or volume/time

mg O2/l/t

Estimating Primary Productivity

In a bottle of known volume, incubate for a whole day.

P and R →

← R

1) Measure the increase in oxygen over a given period of time2) Measure the uptake of labeled carbon (14C) by the phytoplankton.

GROSS Primary Production Rate

NET Primary Production Rate

Pg – R = Pn

Measuring Primary Production (PP)Measuring Primary Production (PP)

photoinhibition

PhotosynthesisIs a function of VISIBLE LIGHT

Photosynthetically Available Radiation (PAR)Quantity of light that stimulates photosynthesis

The relationship between Photosynthesis and Irradiance (PAR) is called the P-I CURVE

Photosynthesis – Irradiance Curve

• P is the photosynthesis rate (matter / volume*time)• I is the irradiance, light intensity (cal cm-2 min-1)

1 cal cm-2 min-1 (PAR) =3.15x10-4 μmol m-2 s-1

P

Irradiance (I or E)

Photosynthesis – Irradiance Curve

• Pmax is the maximal rate of photosynthesis• Ik is the irradiance saturation parameter (varies for

different plants)• is the initial slope of the P vs. I curve

P

Irradiance (I or E)

Pmax

Ik

Photosynthesis – Irradiance Curve

• Ib is the irradiance at which photoinhibition occurs

• is the decrease in P with increasing irradiance under photoinhibition.

P

Irradiance (I or E)

Pm

IkIb

Photosynthesis – Irradiance Curve

• Changes in reflect changes in the light harvesting capacity and efficiency of the light reactions of photosynthesis (cellular properties)

• Changes in Pm reflect changes in the enzymatic capacity (e.g. the dark reactions of photosynthesis).

P

Irradiance (I or E)

Pm

IkIb

Photosynthesis – Irradiance Curve

• Photoinhibition reflects damage (reversible or irreversible) to the photosynthetic system … can be caused by UV damage and excessive visible light flux, modulated by time of exposure.

P

Irradiance (I or E)

Pm

IkIb