Upload
duc
View
40
Download
0
Embed Size (px)
DESCRIPTION
Nutrient Dynamics in Estuarine and Coastal Marine Ecosystems. Daniel Conley 1 , Peter M.J. Herman 2 and Vincent Escaravage 2. 1 Department of Marine Ecology, National Environmental Research Institute, Roskilde, Denmark and Department of Marine Ecology, Institute of Biological - PowerPoint PPT Presentation
Citation preview
Nutrient Dynamics in Estuarine and Coastal Marine Ecosystems
Daniel Conley1, Peter M.J. Herman2 and Vincent Escaravage2
1Department of Marine Ecology, National Environmental Research Institute, Roskilde, Denmark and Department of Marine Ecology, Institute of Biological Sciences, University of Aarhus, Denmark
2Netherlands Institute of Ecology, Centre for Estuarine and Marine Ecology, The Netherlands
Why nutrients?
Introduction
Significant advances within the last 2 decades ELOISE, LMER/LTER, LOICZ, National
Nutrient inputs
Sources, quantification, ratios, time
Coastal zone as an active transformer of nutrients
N, P, Si, limitation and eutrophication
Final thoughts
Wade et al. 2002
Modelling N transfer from catchments to estuaries using deterministic models
Integrated Nitrogen Model for European catchments (INCA)
Smith et al. 1997
Modelling N transfer: SPARROWSPAtially Referenced Regressions On Watershed Attributes
Empirically derived estimates from in stream measurements
Estimated nitrogen export (kg/km2/yr)
Alexander et al. 2000
A rapid decline in the rate of nitrogen loss with channel size
Proximity of sources to large streams and rivers is a major determinant of N transport
Billen and Garnier 2002
River Strahler Model Complex
Garnier et al. 2002
Ratios of inputs of N, P and Si have changed with time
0
1
2
3
4
5
0 60 120180240300360
days
10
^3 T
/da
y
0
0.05
0.1
0.15
0.2
0 60 120 180240300360
days
10
^3 T
/da
y
0
1
2
3
0 60 120 180240300360
days
10
^3 T
/da
y
0
1
2
3
4
5
0 60 120 180 240300 360
days
10^3
T/d
ay
0
0.05
0.1
0.15
0.2
0 60 120180240300360
days
10^3
T/d
ay
0
1
2
3
0 60 120180240300360
days
10^3
T/d
ay
N-DIN
N-DIN
P-PO4
P-PO4
DSi
DSi
River Strahler applied to the Danube for periods 1988-91 and 1994-95 Nitrogen loading reductions
Large reductions in phosphorus loading
Formulations for Si are primitive
Long-term changes in DSi transport from building of dams, eutrophication of lakes, and land-use practices
De Leeuw et al. 2002
Modelling atmospheric nitrogen depositionDe Leeuw et al., 2003
30% of N loading from atmospheric deposition
Wet deposition represents 81% of N deposition
Identify sources of N
But…
Needs improved temporal and spatial resolution
P deposition?
ANICE and MEAD projects
Buddemeier 1997
SCOR/LOICZ Working Group onground water inputs
Estimates of groundwater fluxes are necessary for nutrient budgets
Important, but fluxes are notoriously uncertain
Harmonized Procedures for quantificationof nutrient losses from diffuse sources (HARP)
Developing harmonized modelling tools for integrated basin management
Darracq and Destouni 2004
Model assumptions influences final result
Used different spatial process and parameter aggregation procedures
Figure a - A 50% N reduction could be achieved by focusing on eastern basin
Figures b and c predict that reductions should be spread over entire basin
Economic and societal consequences
What about nutrient loading in the past?
Clarke et al. 2003
Monitoring Long-term Trends in Eutrophication and Nutrients in the Coastal Zone (MOLTEN)
TNincreasedfrom ca.
45 to 90 Min the last50 years
Bradshaw and Rasmussen 2004
2000
1500
1000
500
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Ca
len
da
r y
ea
r B
C /
AD
20 40 60 80 100
Tree
s
Shrubs
& Dw
arf S
hrubs
Herbs
20
% of sum terrestrial pollen and spores
Hordeu
m ty
pe
20
Secal
e ce
real
e
20
Cannab
is ty
pe
50 100 150
mg cm-2 yr-1
Min
erogen
ic m
atte
r
a
ccum
ulatio
n rate
100 200 300
µg TP L-1
Diato
m-in
ferre
d TP
Period
MoT
MED
LIA
RIA
PRIA
LBA
EBA
LN
MNB
MNA
EN
MESO
Dallund Sæ, Denmark
1900
1920
1940
1960
1980
2000
Yea
r
0
C. men
eghin
iana
0
Melo
sira
mon
ilifor
mis
0 20
Coscin
odisc
us a
stero
mph
alus
0 20
Deton
ula co
nfer
vace
a RS
0
Cyclot
ella
choc
tawha
tchee
ana
0 20
% abundance
Opeph
ora
mut
abilis
0 20
Cocco
neis
place
ntula
0 20
C. scu
tellu
m
0
Fragil
aria
ellipt
ica a
gg.
0 20
Tabula
ria fa
sicula
ta a
gg.
30 50 70 90 110
Diatom
-infe
rred
TN
Planktonic Benthic
µmol l-1
Active area of research and development
Summary of land side
Importance for management, e.g. WFD
Need for scenarios
Models, models and more models
Risgaard-Petersen 2003
Significant advances in our understanding of the nitrogen cycle
Sediment microalgae are strong competitors for nitrogen
Strongly reduced denitrification in autotrophic sediments
Seagrass communities also play an important role in N transformations
NH4+ + NO2
- = N2 + H2OKnown to occur in WWTP
Discovery of anaerobic ammonium oxidation (ANAMMOX) in the marine
environment
Accounts for up to 65% of N2
production on shelf sediments
ANAMMOX is responsible for a significant part of the global N2 production (25-50 %)
Dalsgaard et al. 2003
Stedmon et al. 2004
Cycling of Dissolved Organic Nitrogen (DON)
DON 12%PON 7%
DIN 81%
River inputs of N to Horsens Fjord, Denmark
Inputs dominated by nitrate
DIN 17%PON 0%
DON 83%
Export from Horsens Fjord
Extensive transformations Export primarily as DONAvailability?Impact on food webs?Impact on coastal zone?
N2O and N cycling
NH4 NO2 NO3
N2
NO
N2O
Nitrification
DenitrificationOxic Anoxic
N2O is a greenhouse gas 100x more powerful than CO2
de Bie et al. 2002
0
200
400
600
N2O
(n
M)
NH
4 (µ
M)
0
50
100
150
OO2 2
(%sa
t)(%
sat)
0 5 10 15 20 25 30 35
Salinity
Peak N2O production in the Schelde estuary at low O2 concentrationsLow oxygen and some NH4
triggers N2O production in estuaries
Long-term monitoring records of dissolved silica (DSi) show declining concentrations in the Baltic with eutrophication and damming of riversDSi concentrations are generally not limiting today
Within the next 20-30 years DSi limitation will be common causing severe disruption of food webs in the Baltic Sea
Papush, Danielson and Rahm (Unpub. Data)
Long-term reductions in dissolved silicate in the Baltic Sea
Lancelot et al. 2002
Effects of N, P and Si concentrations and ratios
NAN
DIA
BAC
POM
DOM
Si
PO4
MZoo
µZoo
NO3
NH4
Sediment
OPP
NOCGEL
Recognition that differential loading of N, P and Si will effect the response of coastal ecosystems
Reductions in Si inputs disrupts diatom-based food web
Changes in N:P ratios will effect functional groups of algae
0
2
4
6
8
10
0 60 120 180 240 300 360
mgC
hla/
m3
dia
Naf
opp
0
10
20
30
40
0 60 120 180 240 300 360m
gC/m
3
cop
mcz
bac
0
10
20
30
40
0 60 120 180 240 300 360
mg/
m3
mne
noc
0
2
4
6
8
10
0 60 120 180 240 300 360
mgC
hla/
m3
dia
Naf
opp
0
10
20
30
40
0 60 120 180 240 300 360
mgC
/m3
cop
mcz
bac
0
10
20
30
40
0 60 120 180 240 300 360m
gC/m
3
mne
noc
a
b
Lancelot et al. 2002
Response of functional groups to nutrient forcing in the Danube River
1988-91
1994-95
diatomsnano flagellatesopportunistic species
copepodsmeso zooplanktonbacteria
MnemiopsisNoctiluca
Model used as a tool to assess changes in loads
Higher nutrient loads increased the diatom- copepod C transfer, but opportunistic species thrive later
Lowered nutrient levels enhanced the microbial food web
Combining model results with increased fishing pressure demonstrated that BOTH were important
De Wit et al. 2001
Regime shifts under eutrophication
Responses to eutrophication not always linear
Increase the load of nutrients until a sudden shift in ecosystem structure occurs
THRESHOLDSTHRESHOLDS
Coupled models of input and response needed
Summary
Data, data, data
From a recent EEA Assessment of marine eutrophication in Europe
Coupled models of input and response needed
Summary
Data, data, data
There is a need for long-term ecological research
Thank youvery many!