nutrient use by cyanobacteria in subtropical reservoirs

Nutrient use by cyanobacteria in subtropical reservoirs

Michele Burford

Tim Davis, Priya Muhid, Matt Prentice Australian Rivers Institute

Stratified lakes & reservoirs promote cyanobacteria

Key questions

Should we invest in controlling nutrient inputs?

How do we decide whether nutrient inputs

are a problem? Nutrient concentrations Nutrient ratios Algal measures – chl, algal #, toxins

PN PN

PN

PN

PN PN

PN PN PN

PN 10 days supply

PN PN

1 day supply

Algal bioassays

N, P and N+P additions Photosynthetic yield

response (PHYTOPAM) after 24-48 h

Typically co-limited in

summer

Muhid & Burford, in press Inland Waters

Mesocosm experiments

Experimental design

Treatments Control Nitrate Urea Phosphate Nitrate + phosphate Urea + phosphate

Background nutrients

mg/L DIN + urea DIP DN:DIP

Expt 1 0.032 0.004 19:1 Expt 2 0.019 0.004 12:1

Biovolum

e  (x10

7  µm

3  mL-­‐1)  

Biovolum

e  (x10

7  µm

3  mL-­‐1)  

Ambient Control Nitrate Urea PhosphateNitrate + P Urea + P

Cyanobacteria Diatoms Chlorophytes CryptophytesChrysophytes Dinoflagellates Euglenophytes

Ambient Control Nitrate Urea Phosphate Nitrate + P Urea + P

Experiment  1   Experiment  2  

3  

2  

1  

0  

3  

2  

1  

0  

T. Davis, unpubl. data

Urea + P stimulated phytoplankton

C. raciborskii response

0.0E+00

4.0E+06

8.0E+06

1.2E+07

1.6E+07

0.0E+00

4.0E+06

8.0E+06

1.2E+07

1.6E+07

AmbientT0

Ambient

Contro

l

Nitrate

Urea

Phosp

hate

Nitrate+

P

Urea+P

AmbientT0

Ambient

Control

Nitrate

Urea

Phosp

hate

Nitrate+

P

Urea+P

Cel

l bio

vol.

(€m

3 ml-1

) *

Expt 1

Expt 2

Expt 3

Cylindrospermopsins cell quota

0.00E+00

2.00E-07

4.00E-07

6.00E-07

8.00E-07

AmbientT

0

Ambient

Contro

l

Nitrate

Urea

Phosp

hate

Nitrate+

P

Urea+P

QTCYN

QdeoxyCYNQCYN A

A

A + B

A + B

BB B

Source:  Google  Earth  

1  

2  

3  

4  

Upper  reservoir  zone  

Mid  reservoir  zone  

Lower  reservoir  zone  

Source:  Badin  Gibbes  

33P-phosphate uptake studies

Lake Wivenhoe, Queensland

Monthly sampling Four sites

Rapid P uptake

M. Prentice, unpubl. data

Threshold value

Uptake by starved C.raciborskii

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25 30

Specific  DIP  up

take  rate

[µg  DIP  µg  Chl  a

L-­‐1hr

-­‐1]

Days  post  T=0

P P

Active uptake

organicP

Slow use

Conclusions

Nitrogen and phosphorus promotes algal growth

Cyanobacteria have an active uptake mode

Measuring nutrient conc is of limited value

Acknowledgements Students & staff

– A.Chuang, S.Faggotter, C. Laurikaunen, C.Polson Collaborators

– Seqwater (P.Orr) – B.Neilan, J.Beardall, K.O’Brien, D. Hamilton Funding sources

Seqwater, Aust. Research Council, Griffith University

Species which grew

Expt 1 Expt 2 Expt 3

Monoraphidium Achnanthidium Synedra C. raciborskii Planktolyngbya

Achnanthidium Aulecoseira Synedra C. raciborskii Peridinium Cryptomonas

Aulecoseira C. raciborskii Planktolyngbya

Reservoirs in subtropical Australia

Tropic of Capricorn

Burford et al. 2012 Aquat Sci Burford et al. 2012 Aquat Sci

0.002

0.006

0.01

0.014

0.018

0

0.02

0.04

0.06

0.08

0.1

0.12

0.002

0.0025

0.003

0.0035

0.004

Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09

Ammonium

Nitrate + nitrite

Phosphate

Con

c (m

g L-1

)

Burford et al 2012

N+P increased chlorophyll a

0

20

40

60

80

0

20

40

60

80

Ambient

Contro

l

Contro

l

Nitrate

Urea

Phosp

hate

Nitrate+P

Urea+P

Chl

a (¬ g

L-1

)Expt 1

Expt 2

Background nutrients

mg/L DIN + urea DIP DIN:DIP Post floods 0.138 0.004 76:1 Expt 3 0.044 0.006 16:1

Post inflow event Biovolum

e  (x10

7  µm

3  mL-­‐1)  

Ambient Control Nitrate Urea Phosphate Nitrate + P Urea + P

Cyanobacteria Diatoms Chlorophytes CryptophytesChrysophytes Dinoflagellates Euglenophytes

1.6  

1.2  

0.8  

0.4  

0  

Experiment  3  

Euphotic depth half previous experiments