Hans Paerl PhD

Nitrogen-Eutrophication
Nitrogen Eutrophication
Dynamics in Estuaries
Hans Paerl, UNC-CH UNC CH Institute of Marine Sciences, Morehead City, NC
www.marine.unc.edu/Paerllab

•
Key Estuarine Nutrient Issues
Primary production in estuarine waters is largely N limited;
however some systems are N & P co-limited co limited or P limited
•
•
N (& P) Over-enrichment Over enrichment linked to eutrophication
Sources, forms and proportions of N loading are changing
*
e.g. point & non-point non point surface runoff, atmospheric deposition, groundwater
•
Ammonium is increasing as a N source
Hypoxia, Increased wastewater loads, Ag runoff
•
Ecological Effects?*
* nuisance algal blooms, toxicity, hypoxia/anoxia, food web alterations alterations

Fisher et al. 1998
Nutrient limitation in the Chesapeake Bay
Chesapeake
(Fisher et al. 1998)

Nutrient limitation dynamics in the Neuse
R. Estuary, NC
Neuse R. Estuary
Gallo 2004

Nitrate (μg N L -1 )
1200
1000
800
600
400
200
0
200
150
100
50
0
200
150
100
50
Nitrate Ammonium
Nitrate and Ammonium
Concentrations in the
Neuse R. Estuary, NC
0
Jan Feb Mar Apr May Jun Jul Aug
Paerl et al. 2005;
ModMon Project
Jan Feb Mar Apr May Jun Jul
0
Aug
100
80
60
40
20
0
100
80
60
40
20
0
100
80
60
40
20
Ammonium (μg N L -1 )

% of total measured N uptake
100
80
60
40
20
0
100
80
60
40
20
0
100
80
60
40
20
0
Jan Feb Mar Apr May Jun Jul
Relative uptake of
Ammonium, Nitrate
and Urea in the NRE
Ammonium
Nitrate
Urea
Twomey et al. 2005

•
•
Conclusions (For Neuse R. Estuary)
All forms of N are readily utilized
Uptake of various N forms reflects
their availability & concentrations

Ammonium is often a
preferred N source,and
it is increasing. What
are the effects on phyto
community
structure?
Chlorophyll a (µg L -1 )
80
70
60
50
40
30
20
10
0
C
NH4
NO3
Nutrient Addition Bioassay Experiment, T1
Neuse River, July 2003
Upstream CMAX Downstream
NH4 + NO3
P
NH4 + P
NO3 + P
NH4 + NO3 + P
C
NH4
NO3
NH4 + NO3
P
NH4 + P
NO3 + P
NH4 + NO3 + P
C
NH4
NO3
Twomey et al. 2005
NH4 + NO3
P
NH4 + P
NO3 + P
NH4 + NO3 + P

All phytos
Concentration
(mg m-3 )
cryptophytes
15
12
9
6
3
0
5
4
3
2
1
0
Bogue Sound Bioassay August, 1996
Chl a Fucoxanthin
12
Control Nitrate Ammonium
Control Nitrate Ammonium
15
9
6
3
0
3
2
1
0
Control Nitrate Ammonium
Alloxanthin
5
4
Zeaxanthin
Treatment
Control Nitrate Ammonium
diatoms
cyanobacteria
Paerl et al. 2006

N source can affect
cyanobacterial dominance:
Lake Njupfatet, Sweden
Blomqvist et al. 1994
+ ammonium-N
ammonium
+ nitrate-N nitrate

Lake Taihu
3 rd largest lake in China. Increased N loads (dominated by
ammonium) . Blooms have grown to “pea pea soup” soup conditions within a decade

Freshwater discharge and residence time matter as well
Hydrologic controls of chl-a chl chl-a production and composition:
SeaWiFS (SAS II) during low flow (’95) ( (’95) 95) and high flow (’96) ( (’96) 96) years
spring ‘95 spring ‘96
Harding et al. 2006

Chesapeake Bay phytoplankton
composition by CHEMTAX –
contrasting flow years
spring '95
spring '96
summer '95
summer '96
Diatoms
Dinoflagellates
Cryptophytes
Cyanophytes
Chlorophytes
Prasinophytes
Haptophytes
Adolph et al 2007

Nutrient cycling and food web implications
Nutrient and
Hydrologic drivers
PHYTOPLANKTON
COMMUNITY
FORM of Limiting Nutrient
(NO 3 - , NH4 + , DON)
Nutrient Ratios, Residence Time
Grazed
Phytoplankton
Species
Nuisance / Toxic
Phytoplankton
Species
Some Dinoflagellates
Cyanobacteria
Nutrient Regeneration
Decomposition of POM
Linkages Between Nutrient Inputs, Hydrology,
Phytoplankton Community Composition, Grazing,
Hypoxia and Fisheries Habitat
Grazing and
Water Column
Carbon Recycling
Carbon
Deposition
(POC)
+
DECREASED
O 2 Depletion
Potentials
INCREASED
O 2 Depletion
Potentials
-
OXIC
CONDITIONS
Mixing
PHYSICAL
CONTROLS
Stratification
HYPOXIA
ANOXIA

•
•
•
•
•
•
Management Implications
In most estuaries, including regions of the SFO Bay N
plays role as limiting nutrient.
DIN utilization reflects supply rates: However, some
forms (e.g., ammonium) may be preferred.
Sources of N influence algal composition: Potential
food web and biogeochemical implications
Light-N Light N interactions may be important, especially in
turbid waters
Hydrology (storms, floods, droughts) and residence
time are important interactive variables, especially for
slower growing phytoplankton like cyanobacteria.
cyanobacteria.
Develop appropriate in in situ situ response assays and
indicators to assess responses and impacts

Thanks to:
L. Harding
A. Joyner
B. Peierls
M. Piehler
K. Rossignol
L. Valdes
P. Wyrick
Estuarine & Coastal Indicators of Nutrient Enrichment
www.unc.edu/ims/paerllab/
www.unc.edu/ims/paerllab
www.unc.edu/ims/paerllab/
82667701
& NSF, USDA, NCDENR, NC Sea Grant

Effects of Ammonium or Nitrate (10 μg N L -1 )
Blomqvist et al. 1994
additions (+P) on
phytoplankton biomass in eutrophic Lake Erken, Sweden

Lake Okeechobee, Florida: Nutrient enrichment,
water withdrawal, drought conditions. Lots more ammonium
2007
Photo, K. Havens

Expansion of
Cylindrospermopsis
Raciborskii
Raciborskii
Why?

Nutrient/light strategies of Cylindrospermopsis
ylindrospermopsis raciborskii raciborskii
High P uptake and storage capacity
(Isvanovics Isvanovics et al 2000)
N 2 Fixer
High NH4 NH
+ uptake affinity
N additions (NH4 (NH
+ NO x) ) often significantly increase growth (chl ( chl a
and cell counts) and productivity (Presing Presing et al 1996)
Tolerates low light intensities
“Tracks Tracks” eutrophication (expand in waters w/ increasing turbidity)
Can coexist in water column with other cyanoHABs
(Fabbro Fabbro and Duivenvoorden 1996)

N stimulation of primary production in the
Coastal W. Atlantic Ocean
Paerl et al., 1999
14 C-CO 2 Fixation (DPM * 10 4 )
*
0.6
*
0.4
0.2
0
7.5
5
2.5
0
Control
NO3
*
NH4
PO4
Fe + EDTA
Fe + EDTA + NO3
*
Gulf
Stream
Inshore

DPM/ml
N (+P) stimulation of primary
production in the brackish
Baltic Sea
700
600
500
400
300
200
100
Baltic Sea 2000, Bioassay A
Primary Productivity
Legend
Day 1
Day 2
Day 3
Control
Mannitol
N
P
Fe
Fe+EDTA
N+Fe
P+Fe
N+P
Chlorophyll a (μg/l)
0.13
0.12
0.11
0.1
0.09
0.08
0.07
0.06
0.05
0.04
0.03
Baltic Sea 2000, Bioassay A
Chlorophyll
Control
Mannitol
N
P
Fe
Fe+EDTA
N+Fe
P+Fe
N+P

Distance Downstream (km)
River Discharge (m 3 s -1 )
40
30
20
10
0
40
30
20
10
0
40
30
20
10
0
500
400
300
200
100
0
1994
1995
Phytoplankton functional group responses
1996
1997
1998
1999
2000
2001
2002
2003
2004
8
6
4
2
0
12
9
6
3
0
16
12
8
4
0
Chlorophytes
(µg L-1 )
Cyanobacteria
(µg L-1 )
Dinoflagellates
(µg L-1 )
Bertha
Fran
Bonnie
Dennis
Floyd
Irene
Isabel

DIN DI
What do the data show?
Loading vs. primary production in a range of N. American
and European estuaries
(Nixon 1996)

N loading and algal production in the Neuse R. Estuary
distance downstream
from Streets Ferry Bridge (km)
50
40
30
20
10
0
50
40
30
20
10
0
50
40
30
20
10
0
Salinity (psu)
chl a (ug L -1 )
- -1 NOx (ug L )
Floyd
6/97 12/97 6/98 12/98 6/99 12/99 6/00
20
15
10
0
200
400
600
800
>1000
>30
20
10
0
5
0