Epilithic abundance and composition: Influences on allochthonous - - PowerPoint PPT Presentation

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Epilithic abundance and composition: Influences on allochthonous and autochthonous nitrogen sources Kimberly Bray 1 , Marc Peipoch 2 , & H. Maurice Valett 1 1 University of Montana, 2 Stroud Water Research Center Peterson et al. 2001,

SLIDE 1

Epilithic abundance and composition: Influences on allochthonous and autochthonous nitrogen sources

Kimberly Bray1, Marc Peipoch2, &

H. Maurice Valett1

1 University of Montana, 2 Stroud

Water Research Center

SLIDE 2

Peterson et al. 2001, Science

SLIDE 3

Biota

N fixation

Norg

Autochthonous

NO3

NO3
nitrate uptake

Allochthonous

SLIDE 4

SLIDE 5

Clark Fork River

Source: Clark Fork Coalition

SLIDE 6

Nutrient Concentrations

From Tri-State Water Quality Council 2009

Phosphate Nitrate Discharge

SLIDE 7

Redfield Ratio

Alfred Redfield Source: NOAA

Ratio of C:N:P in oceanic phytoplankton = 106:16:1

SLIDE 8

Nutrient Concentrations

SRP Nitrate Redfield Ratio

SLIDE 9

Cladophora algae

Chl a AFDM

Epilithic OM and chlorophyll a

SLIDE 10

Seasonal Cladophora bloom: A conceptual diagram

Cladophora discharge

SLIDE 11

Nostoc cyanobacteria: a blue-green “algae”

NO3

SLIDE 12

Facultative Nitrogen Fixation N  N + 8 H+ + 8 e- 2 NH3 + H2

stream conditions:

High levels of PAR
Slow moving water
High phosphate concentrations
Low nitrate concentrations
High temperatures

Nostoc cyanobacteria

nitrogenase

SLIDE 13

Nostoc

Seasonal succession of periphyton: A conceptual diagram

Cladophora discharge

SLIDE 14

Nostoc

Seasonal succession of periphyton: A conceptual diagram

discharge Autochthonous N Cladophora Allochthonous N

SLIDE 15

Source: Clark Fork Coalition

Key questions:

What is the role of allochthonous and autochthonous

nitrogen sources in determining epilithic biomass over a summer growing season?

How do environmental conditions influence N fixation

rates?

SLIDE 16

Drummond, MT

Diel Study Site Summer-long Study Site

University

f Montana

Missoula

Study Sites

SLIDE 17

Sampling Timeline

July 31st Aug. 14th Aug. 28th Sept. 8th Aug. 9th Seasonal sampling: 9 replicates per round Metrics

N fixation rates
Instream nutrient concentrations (ammonium,

nitrate, phosphate)

Dissolved oxygen concentrations
Temperature
PAR
Epilithic composition and abundance
Chlorophyll a

Diel sampling: 3 replicates every 2.5 hours

SLIDE 18

H  C  C  H + 2H+ + 2 e- H2  C = C  H2

nitrogenase

Acetylene Reduction Technique

SLIDE 19

Cell Counts

Green algae Cyanobacteria

SLIDE 20

Seasonal N fixation

SLIDE 21

Highest [NO3

]

& [NH4

Phosphate Ammonium Nitrate

Seasonal N fixation and nutrient concentrations

Concentration (µg N or P/L)

Lowest [NO3

]

& [NH4

SLIDE 22

Date AFDM (g / m2)

10 20 30 40

Date

Y Data

200 400 600 800 1000 1200 1400 1600 1800

Cell Abundance (# / field of view)

Nostoc Clado.

Epilithic OM (g AFDM / m2)

Seasonal trends in epilithic biomass and periphyton composition

SLIDE 23

Night

Diel N fixation

0.19 ± 0.13 0.03 ± 0.006

SLIDE 24

Environmental influences on diel N-fixation

Temperature (°C) N fixation (µg N/m2/hr) 0.2 0.4

R2 = 0.36 p = 0.027

200 400 600 PAR (mmol m-2S-1) 15 0.2 0.4 20 25 30

R2 = 0.36 p = 0.019

35 N fixation (µg N/m2/hr)

SLIDE 25

Metabolic Demand: Temperature dependence of N fixation

Temperature (1/kT) Activation energy = 1.34 eV

From Welter et al. 2015

Arrhenius Relationship: ln N fixation = −Ea kT + ln A

SLIDE 26

Conclusions

Environmental Constraints:

Temperature
PAR
Nutrient

concentrations

Epilithic

composition

from Grimm and Petrone 1997

SLIDE 27

Source: NY State Department of Environmental Conservation

SLIDE 28

Source: Clark Fork Coalition

SLIDE 29

Acknowledgements

Maury Valett
Marc Peipoch
Amy Marcarelli
Erin Eberhard
Patrick Hurley
Carly Andlauer

"This material is based upon work supported in part by the National Science Foundation EPSCoR Cooperative Agreement OIA-1757351"