Primary production rates under Primary production rates under varying light, temperature and varying light, temperature and

biomass conditionsbiomass conditions

Michael D. YardMichael D. YardDean W. BlinnDean W. Blinn

Northern Arizona UniversityNorthern Arizona University

Determine primary production rates for the Determine primary production rates for the phytobenthic community under a range of phytobenthic community under a range of

environmental conditionsenvironmental conditions

• Light and temperatureLight and temperature

• Determine how production Determine how production rates responded to these rates responded to these same factors under greater same factors under greater biomass accumulation.biomass accumulation.

• Develop a production model Develop a production model to estimate standing biomass to estimate standing biomass accrualaccrual

Photosynthesis is a light driven Photosynthesis is a light driven Re/dox ProcessRe/dox Process

COCO22 + H+ H22O O CHCH22O + OO + O22

hνhν

P680

P680

P700

P700H2O4

Mn Yz

Pheo

200 ps

QAQB

PQ

Cyt

ochr

ome

b 6/f

com

plex

PQ

A0

1-15ms

1 ms

150-600 μs

1 ms200 μs

O2 hνhν

hνhν

A1

FX

FA/FB

Fd

3 ps

40-200 ps

15-200 ns

2 μs

P680

P680

P700

P700H2O4

Mn Yz

Pheo

200 ps

QAQB

PQ

Cyt

ochr

ome

b 6/f

com

plex

A0

1-15ms

1 ms

150-600 μs

1 ms200 μs

Photosystem IPhotosystem I

Photosystem IIPhotosystem II

METHODOLOGYMETHODOLOGY

• Multivariate approachMultivariate approach– TemperatureTemperature

• 11, 16 & 20 C11, 16 & 20 COO

– LightLight

– Biomass (g mBiomass (g m-2 -2 ss-1-1))

• Net photosynthetic ratesNet photosynthetic rates– 30 min 30 min

• Respiration ratesRespiration rates– 30 min 30 min

• PhytobenthosPhytobenthos– Cobble substrateCobble substrate– Harvested & TranslocatedHarvested & Translocated

• Predominantly Predominantly CladophorCladophoraa• MAMBMAMB

• Acclimated to prescribed temperatureAcclimated to prescribed temperature– 48 h minimum 48 h minimum – Recirculating pumpsRecirculating pumps– Maintain temperature (±1CMaintain temperature (±1Coo))– WQ (pH, nutrients & temp)WQ (pH, nutrients & temp)

• Samples Samples – 3 to 4 cobbles per chamber 3 to 4 cobbles per chamber – 3 replicates per sample3 replicates per sample– 30 samples per temperature30 samples per temperature

• Closed system Closed system – Lexan chambers Lexan chambers (25cm x 22cm)(25cm x 22cm)

– 30 L capacity30 L capacity– O-rings sealsO-rings seals

• Internal recirculating pumpInternal recirculating pump– Inline pumps Inline pumps – Flow rate 50 L / minFlow rate 50 L / min

• Oxygen generation Oxygen generation was monitored was monitored – YSI DO sensor (3)YSI DO sensor (3)

– Data logger, YSI-Data logger, YSI-Model 52 (3)Model 52 (3)

• Digitally loggedDigitally logged– Time interval, 1 min Time interval, 1 min

• TemperatureTemperature– Internally monitoredInternally monitored

– Digitally loggedDigitally logged

• Rheostatic controlRheostatic control– Water heating elementWater heating element

– 120 V AC120 V AC

– 5500 W generator5500 W generator

• Light intensity was continuously Light intensity was continuously monitoredmonitored

• LICOR, IncLICOR, Inc– LI 1000 Data LoggerLI 1000 Data Logger

– Scalar IrradianceScalar Irradiance• PAR (400-700 nm)PAR (400-700 nm)

• μmol mμmol m-2-2 s s-1-1

– External measurementExternal measurement• Readjusted to account for the internal light Readjusted to account for the internal light

environment of the different chambers environment of the different chambers

• Light QuantityLight Quantity– Attenuation of underwater light is a Attenuation of underwater light is a

function of depth function of depth

– Quantity of light received was regulated Quantity of light received was regulated by vertical adjustmentsby vertical adjustments

• Respiration RatesRespiration Rates– Light chamber coversLight chamber covers– 30 min30 min– maintained tempmaintained temp

– monitored Omonitored O22 consumption consumption

• Volume calculationVolume calculation– Cobble displacementCobble displacement

• AFSM DeterminationAFSM Determination– DriedDried– Weighed Weighed – AshedAshed

• DO ratesDO rates– NormalizedNormalized

• mg Omg O22 g C g C-1-1 m m-2-2 h h-1-1

-1.5

-0.5

0.5

1.5

2.5

3.5

0:00 0:15 0:30 0:45

TIME (Hr)

mg

O2 L

-11150 uE

600 uE

180 uE75 uE

Irradiance

Respiration (light-phase)

Net Production Rates

1427 mg O2 m-2 h-1

819 mg O2 m-2 h-1

372 mg O2 m-2 h-1

225 mg O2 m-2 h-1

Respiration (light-phase) -300 mg O2 m-2 h-1

9.77 mg O2 gC m-2 h-1

5.97 mg O2 gC m-2 h-1

3.62 mg O2 gC m-2 h-1

Net Production Rate

Respiration Rate -2.5 mg O2 gC m-2 h-1

2.12 mg O2 gC m-2 h-1

0

5

10

15

20

25

0 250 500 750 1000 1250 1500 1750 2000

QUANTA (umol m-2 s-1)

mg

O2 g

C-1

m-2

h-1

16oC

11oC

20oC

1 g AFSM

Pmax

Ek

0

5

10

15

20

25

0 500 1000 1500 2000

QUANTA (umol m -2 s -1)

mg

O2 g

C-1

m-2

h-1 16

oC

11oC

20oC

75 g AFSM

Pmax

Pk

0

5

10

15

20

25

0 500 1000 1500 2000

QUANTA (umol m-2 s-1)

mg

O2 g

C-1

m-2

h-1

150 g AFSM

16oC

11oC

20oC

Pmax

Pk

-5

0

5

10

15

20

25

0 400 800 1200 1600 2000 2400

TIME

mg

O2 g

C-1 m

-2 h

-1

Respiration (light-phase)

Respiration (dark-phase)

01 June 2000Lees Ferry

Direct Solar InsolationGross Photosynthesis Net Photosynthesis

NPPNPP = PG - RL - RD

Production assumption:Production assumption:

• No turnover or lossNo turnover or loss

• cellular damage leakage of cellular damage leakage of photosynthates (DOC)photosynthates (DOC)

• senescent growthsenescent growth

• physical shear forces, breakage of physical shear forces, breakage of filamentous structurefilamentous structure

• grazinggrazing

Biomass Accrual

0

50

100

150

200

250

300

350

0 20 40 60 80

DAYS (Summer Period)

g C

m-2

(A

FD

M)

16 C0

20 C0

10 C0

1.2 m Depth1.2 m DepthOptics .28Optics .28

Production assumption:Production assumption:

• No turnover or lossNo turnover or loss

• ResponseResponse– Optics remain the same, similar to Optics remain the same, similar to

Lees FerryLees Ferry

– Available light attenuates as a Available light attenuates as a function of depthfunction of depth

– Appreciable reduction in biomassAppreciable reduction in biomass

4 m Depth4 m DepthOptics .28Optics .28

Biomass Accrual

0

50

100

150

200

250

300

350

0 20 40 60 80

DAYS (Summer Period)

g C

m-2

(AF

DM

)

10 C0

20 C0

16 C0

Production assumption:Production assumption:

• No turnover or lossNo turnover or loss

• ResponseResponse– Optics are altered, similar to Optics are altered, similar to

Western Grand Canyon (Ko = 0.90)Western Grand Canyon (Ko = 0.90)

– Surface production approximating Surface production approximating 1m depth1m depth

– Comparable biomass accrual to Comparable biomass accrual to Lees Ferry at 4 m depthLees Ferry at 4 m depth

1 m Depth1 m DepthOptics .90Optics .90

Biomass Accrual

0

50

100

150

200

250

300

350

0 20 40 60 80

DAYS (Summer Period)

g C

m-2

(A

FD

M)

20 C0

10 C0

16 C0

Production assumption:Production assumption:

• No turnover or lossNo turnover or loss

• ResponseResponse– Optics are similar to Western Grand Optics are similar to Western Grand

Canyon (Ko = 0.90)Canyon (Ko = 0.90)

– Surface production approximating Surface production approximating 4m depth4m depth

– Production light limitedProduction light limited

4 m Depth4 m DepthOptics .90Optics .90

Biomass Accrual

0

50

100

150

200

250

300

350

0 20 40 60 80

DAYS (Summer Period)

g C

m-2

(A

FD

M)

20 C0

10 C0

16 C0

• Photosynthetic carbon assimilation is Photosynthetic carbon assimilation is enzymatically controlledenzymatically controlled

– Temperature dependent processTemperature dependent process• Electron transport dependent on Electron transport dependent on

membrane fluiditymembrane fluidity

• Intermolecular collision increase ET Intermolecular collision increase ET ratesrates

– Lower TemperaturesLower Temperatures• Reduction in light absorption capacityReduction in light absorption capacity

– Reduced chlorophyll productionReduced chlorophyll production

• Increased photosynthetic capacity Increased photosynthetic capacity – Increased carboxylation activityIncreased carboxylation activity

• Allometry controls photosynthetic carbon Allometry controls photosynthetic carbon assimilationassimilation

– Per unit biomass regulates photosynthetic and Per unit biomass regulates photosynthetic and respiration ratesrespiration rates

– Explanations:Explanations:• Senescent growthSenescent growth

• Intra-spatial competition for limiting factorsIntra-spatial competition for limiting factors

– Self-shading competition for lightSelf-shading competition for light

– Impeding flow, competition for Impeding flow, competition for nutrientsnutrients

Why did an increase in temperature (20 C) result in reducing photosynthetic rates (Pmax)?

• Possible Explanations– Photorespiration response

• Rubisco

– D-ribulose-1,5-bi-phosphate carboxylate/oxygenase

• Decreased photosynthetic efficiency

– Change in epiphytic composition

• Blinn et al. (1989) identified a shift in epiphytic composition

– Thermal stress related to diel variation (48 h acclimation)

AcknowledgementsAcknowledgements

• Northern Arizona UniversityNorthern Arizona University– Aquatic Ecology LabAquatic Ecology Lab

• Allen Haden, Ally Martinez, Molly McCormick, Ian McKinnon, Kim Pomeroy, Joe Shannon, Kevin Wilson, & Allen Haden, Ally Martinez, Molly McCormick, Ian McKinnon, Kim Pomeroy, Joe Shannon, Kevin Wilson, & Nathan ZorichNathan Zorich

– FacultyFaculty• Michael Kearsley, George Koch, Peter Price, & Rod Parnell Michael Kearsley, George Koch, Peter Price, & Rod Parnell

– Instrumentation LabInstrumentation Lab• Charlie BrittonCharlie Britton

– Bilby CenterBilby Center• Tom Huntsberger, & Amy WeltyTom Huntsberger, & Amy Welty

• Grand Canyon Monitoring and Research CenterGrand Canyon Monitoring and Research Center• Dave Baker, Carol Fritzinger, Barry Gold, Susan Hueftle, Barbara Ralston, & Jake TiegsDave Baker, Carol Fritzinger, Barry Gold, Susan Hueftle, Barbara Ralston, & Jake Tiegs

• Mayorga’s WeldingMayorga’s Welding• Frank MayorgaFrank Mayorga

• Humphrey Summit SupportHumphrey Summit Support• Alida Dierker, Brian Dierker, Daniel Dierker & Chris MacIntoshAlida Dierker, Brian Dierker, Daniel Dierker & Chris MacIntosh

• Indispensable InsistenceIndispensable Insistence• Helen YardHelen Yard