LSSF Experiment: Phytobenthic LSSF Experiment: Phytobenthic ColonizationColonization

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

US Geological SurveyUS Geological SurveyGrand Canyon Monitoring and Research CenterGrand Canyon Monitoring and Research CenterNorthern Arizona UniversityNorthern Arizona University

LSSF Experiment: Phytobenthic LSSF Experiment: Phytobenthic ColonizationColonization

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

US Geological SurveyUS Geological SurveyGrand Canyon Monitoring and Research CenterGrand Canyon Monitoring and Research CenterNorthern Arizona UniversityNorthern Arizona University

Is colonization an immediate response upon substrate Is colonization an immediate response upon substrate submersion?submersion?

Or, is there a time-lag? And if so, is this dependent on the degree of prior cobble conditioning?

• When does this When does this newly submerged newly submerged area become area become biologically biologically productive? productive?

Study Objectives

• Determine if there were differential rates in phytobenthic colonization

• Determine most likely mode of propagation

• Determine accrual rates for algae and invertebrates

Sampling Approach

• Treatment Types– 2 Previously Colonized

• Scrapped never desiccated

• Scrapped and desiccated 1 yr

– 1 Never Colonized• (>100 yr)

• Sampling Period – Colonization period (105 d)

– 1 June 2000 to 12 September 2000

• Sampling Trips - 11

• Sampling Frequency– 10 to 12 d sampling interval

• Random block design– Randomly assigned cobbles

– Perpendicular Transects• 11 transects/treatments (3)

and control (1)

• 44 transects

• 20 cobbles/transect

• Randomly Assigned– Sample point location

• Pre-assigned – Transect

– Sample

– Samples independent

• Sampling Template • 4 cm dia.

• Rapid Assessment Procedure (Blinn et al. 1998)

• Field sorted (n = 880) – 14 Gross Categories

» Algae

» Macrophytes

» Invertebrates

– Dry Weight Determination (g)• AFSM Conversion (Shannon

et al. 2000)

• Sampling Approach

Experimental Closure (105 d)

Treatment 1, No previous colonization, exposed > 100 yrTreatment 2, Previously colonized, exposed for 1 yrTreatment 3, Scrapped not exposed to prolonged desiccationControl Cobble

ALGAL BIOMASS

0

1

2

3

4

5

6

7

1 10 20 31 41 51 61 72 82 93 106

TIME

AF

DM

- g

C m

-2

0

10

20

30

40

50

60

70

Treat #1

Treat #2

Treat # 3

• Treatment 1 & 2,– Not significantly different

– Conditioning Trend

• Response Time– 50 to 60 days before it accrued any

appreciable biomass

• Flood Effect– Not significant

– Cobble displacement• 5 %

• Mode of Propigation– Zoospores (80%

• Ulothrix/Zygnematales

• Cladophora

– FragmentationF

all S

pike

Treatment 1 & 2

ALGAL BIOMASS

0

1

2

3

4

5

6

7

1 10 20 31 41 51 61 72 82 93 106

TIME

AF

DM

- g

C m

-2

0

10

20

30

40

50

60

70

80

Treat #1

Treat #2

Treat # 3

• Treatment 3 - Mode of Propigation

– Significantly different

– Basal holdfast structure• Predominantly

Cladophora

• Ulothrix/Zygnematales

– Fragmentation

• Response Time– 10 to 20 days before it

accrued any appreciable biomass

– Increased in biomass• 50 to 60 g m-2 AFDM

– Accrual Rate• 1 g m-2 d-1 AFDM

• Asymptote– 60 days

• Flood Effect– Cobble displacement

• 5 %

Treatment 3

• Invertebrate Composition– 90 to 95% Snail biomass– Maximum biomass

• T1 5.8 g m-2 • T2 11.2 g m-2

– Densities• T1 26 x 103 m-2 • T2 35.5 x 103 m-2

– Treatments 1 & 2• Significantly different

• Response Time– Initial invert biomass

• 0.95 g m-2 (SD 0.5)

– 50 to 60 days before it accrued any appreciable biomass

– Significantly correlated to phytobenthic biomass

INVERT BIOMASS

0

2

4

6

8

10

12

14

16

18

1 10 20 31 41 51 61 72 82 93 106

TIME

AF

DM

- g

C m

-2

0

10

20

30

40

50

60

Treat #1

Treat #2

Treat # 3

• Flood Effect– Significant reduction

between days 93 & 105

Treatment 1 & 2

• Flood Effect– T3 Invertebrate biomass did not significantly

change

– Invertebrate densities did not significantly change

INVERT BIOMASS

0

2

4

6

8

10

12

14

16

18

1 10 20 31 41 51 61 72 82 93 106

TIME

AF

DM

- g

C m

-2

0

10

20

30

40

50

60

Treat #1

Treat #2

Treat # 3

Treatment 3 • Invertebrate Composition– 90% Snail biomass

• Response Time– Immediate response (10 d) – Significantly correlated to

phytobenthic biomass

• Snail biomass– Mean maximum biomass

• T3 38.1 g m-2

• Snail Densities – Mean maximum Densities

• T3 108 x 103 m-2

• Proportion of snail biomass to total biomass

– Treat 1 = 82% (SD 0.16)

– Treat 2 = 73% (SD 0.21)

– Treat 3 = 47% (SD 0.20)

Fal

l Spi

ke

0

50

100

150

200

250

300

0 20 40 60 80 100

DAYS

AF

DM

gC

m-2

Predicted Treat 1 Treat 2 Treat 3 Control

Sum of all Photosynthetic Components

0

50

100

150

200

250

300

0 20 40 60 80 100

DAYS

AF

DM

gC

m-2

Predicted Treat 1 Treat 2 Treat 3 Control

Primary Production Estimate (Assumes no loss)Fall Spike Flow

ALGAL BIOMASS

0

50

100

150

200

250

300

0 20 40 60 80 100

DAYS

AF

SM

(g

m2 )

Treatment 3

CONTROLCladophora 30 to 75% photosynthetic biomass

ALGAL/SNAIL BIOMASS

0

50

100

150

200

250

300

0 20 40 60 80 100

DAYS

AF

SM

(g

m2 ) Snail biomass to high to be supported by algal biomass

• Attained >90 gC m-2; Densities >200 x 103 m-2

• Algal Reduction by Snails (density dependent)

– Hunter 1980

– Mulholland et al. 1983

– Jacoby 1985

– Steinman et al. 1987

– Lowe and Hunter 1988

– Osenberg 1989

– Underwood and Thomas 1990

– Bronmark et al. 1991

– Tuchman and Stevenson 1991

– Hill et al. 1991

– Steinman 1992

– Rosemond et al. 1993

• Algal Biomass increase in response to grazing

– Removal of senescent cells

• Lamberti and Resh 1983

• Swamikannu and Hoagland 1989

– Nutrient cycling

• McCormick and Stevenson 1991

• Stewart 1987

• Mulholland et al. 1991

– Removal of epiphytes

• Dudley 1992

• Sarnelle et al. 1993

ALGAL BIOMASS

0

50

100

150

200

250

300

0 20 40 60 80 100

DAYS

AF

SM

(g

m2 )

Treatment 3

2.1 g/d

ALGAL BIOMASS

0

50

100

150

200

250

300

0 20 40 60 80 100

DAYS

AF

SM

(g

m2 )

Treatment 3

0.6 g /m2 d

2.1 g/m2 d

0

150

300

450

600

750

900

1050

1200

0 20 40 60 80 100

DAYS

AF

DM

gC

m-2

Net Primary Production Model Output, assumes that all net excess production is diverted toward biomass accrual (no loss in photosynthates, drift, grazing)

Asymptote due to balance between net photosynthesis and respiration demands

So, under this model net primary production So, under this model net primary production is self-limiting and constrained by size is self-limiting and constrained by size

0

150

300

450

600

750

900

1050

1200

0 20 40 60 80 100

DAYS

AF

DM

gC

m-2

8.5 gC/m2 dDOC

Consumed by Inverts/Fish

Drift

Structure

Cumulative production through time

4 gC/m2 d

?? gC/m2 d

0.25 gC/m2 d

Conclusion

• Damaged or mechanically removed thallus structure will rapidly recover (Assuming ideal growing conditions)

– If basal holdfast structure remains intact and viable

• Newly submerged substrate has a slower colonization response

– No difference in response for cobbles exposed 1 yr or greater

• Newly submerged substrate has a slower colonization response

– Colonization appears to be predominantly by zoospores

– Fragmentation does not appear to the major propagation mode

– Recovery response may be more rapid if substrate is conditioned

• Microflora (organic material, bacteria, diatom assemblage)

• We cannot be sure if colonization response would be different if grazing pressure was absent

• Stable flows may result in substantial amounts of production

– Both primary and secondary

– However, this may not be apparent by just measuring biomass

– It may be difficult to separate out effects from flows

AcknowledgementsAcknowledgements

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

• Allen Haden, Ally Martinez, Molly McCormick, Ian McKinnon, Joe Shannon Allen Haden, Ally Martinez, Molly McCormick, Ian McKinnon, Joe Shannon – Geology DepartmentGeology Department

• Matt Kaplinsky, & Mark ManoneMatt Kaplinsky, & Mark Manone– FacultyFaculty

• Michael Kearsley, George Koch, Peter Price, & Rod ParnellMichael Kearsley, George Koch, Peter Price, & Rod Parnell

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

Jake Tiegs Jake Tiegs

• Indispensable InsistenceIndispensable Insistence• Helen YardHelen Yard