south american lake gradient analysis impact of climate on shifts in stable states in shallow lakes...
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South American Lake Gradient Analysis
Impact of climate on shifts in stable statesin shallow lakes
Sarian KostenWageningen University
The Netherlands
Project outline
Preliminary results
Research questions
Outline
Temperate shallow lakes tend to be in either of two alternative stable states.
Preliminary work suggests that shallow lakes may be very sensitive to climatic change.
Low nutrient High nutrient
83 lakes
Latitude 5 – 55 degrees south
Sample sites
83 lakes
November 2004 – March 2006
Mid-summer samples
Shallow lakes (average 1.8 m [4.5 – 0.5])
Latitude 5 – 55 south
Low altitude / coastal
Area between 9 and 250 ha.
All sampled by the same team
How do algae react to higher temperatures?• N versus P-limitation?• reach higher concentrations?
How do macrophytes react to higher temperatures?• resist higher turbidities?• disappear at higher nutrient levels?
Does the interaction between algae and macrophytes change at higher temperatures?
Questions
How do algae react to higher temperatures?• N versus P-limitation?• reach higher concentrations?
How do macrophytes react to higher temperatures?• resist higher turbidities?• disappear at higher nutrient levels?
Does the interaction between algae and macrophytes change at higher temperatures?
Questions
Gyllstrom et al., 2005
Huszar et al., 2006
Algae reach a higher biomass – at a given total-P concentration - in colder climates
192 (sub)tropical lakes(Huszar et al. 2006)
N. American & European lakes(Mazumder 1994)
• Both production and respiration will increase but respiration increases relatively more than production
Why do algae reach lower concentrations at a certain nutrient leven when the temperature increases?
(Lopez-Urrutia et al., 2006)
Trophic state
Preliminary results from our study:
Tropicalwith distinct dry season
Tropical – Subtropicalwith and without dry season
Subtropical
Polartundra
Köppen Climate Classification
Total phosphorus (μg L-1)
All lakes Polar Subtropic Tropic
Log Chl-a Log Tot-P
R2
1.5 1.4 1.9 1.6
0.59 0.94 0.56 0.38
Nitrogen limited
Phosphorus limited
Limiting nutrient
Redfield ratioN:P = 16:1
Next 2 slides is I did not show because of lack of time, but isn’t it interesting to see that we have a dominance of N limitation along almost the entire gradient. It will be nice to compare that with other shallow lakes around the globe.
Log Chl-a Log Tot-N
R2
1.1 1.1 1.1 1.1
0.78 0.72 0.81 0.69
All lakes Polar Subtropics Tropics
Total nitrogen (μg/l)
Ch
l-a
(μg
/l)
SLOPE EXACTLY THE SAME FOR ALL REGIONS!!
Overall the algae seem to reach a slightly higher biomass at a given total-P level at higher temperatures
In a comparative study between temperate and artic lakes Flanagan et al. (2003) found higher biomasses at higher temperatures as well.
•Low enzyme activity when cold (Markager et al. 1999)
•Presence of cyanobacteria
•Absence of large zooplankton
Why would warmer be better for algae?
How do algae react to higher temperatures?• N versus P-limitation?• reach higher concentrations?
How do macrophytes react to higher temperatures?• resist higher turbidities?• disappear at higher nutrient levels?
Does the interaction between algae and macrophytes change at higher temperatures?
Questions
Coverage percentage of submerged plants
Average Kd in lakes with a small (<30%) and a large (>30%) coverage of submerged plants
0
2
4
6
8
RN <30 RN >70 RJ <30 RJ >70 UY<30 UY >70 TF<30 TF>70
climate zone
Kd
[m
-1]
Tropical (Sub)tropical Subtropical Polar
Lakes with a coverage percentage of submerged plants <30%
Lakes with a coverage percentage of submerged plants >30%
light intensity (average) at plant canopy
0
50
100
150
200
RN RJ UY TF
climate zone
lig
ht
inte
nsit
y
[E m
-2 m
in-1
]
Tropical (Sub)tropical Subtropical Polar
Maximum nutrient concentration at which submerged macrophytes occur
0
2
4
6
RN RJ UY TF
climate zone
tot
N o
r P
(m
g/l) max tot-P
max tot-N
How do macrophytes react to higher temperatures?
Do they occur at higher turbidities?
Do they occur at higher nutrient levels?
>>> NO
>>> NO
Why?Not only temperature changes but total daily irradiance as well.
Unbalance of data set
How do algae react to higher temperatures?• N versus P-limitation?• reach higher concentrations?
How do macrophytes react to higher temperatures?• resist higher turbidities?• disappear at higher nutrient levels?
Does the interaction between algae and macrophytes change at higher temperatures?
Questions
Polar climate
-100
-50
0
50
100
0.1 0.1 0.4 0.4 0.9 1.0 1.4 5.3
Total-N (mgN/l)
"wa
ter-
cle
ari
ng
-eff
ec
t" o
f s
ub
me
rge
d p
lan
ts (
%)
chl-a
turbidity
Tropical - Subtropical climate
-100
-50
0
50
100
0.2 0.2 0.2 0.3 0.3 0.8 0.9 0.9
Total-N (mgN/l)
"wa
ter-
cle
ari
ng
-eff
ec
t" o
f s
ub
me
rge
d p
lan
ts (
%)
chl-a
turbidity
Subtropical climate
-100
-50
0
50
100
0.0 0.1 0.2 0.2 0.3 0.4 1.0 1.1 1.3 2.4
Total-N (mgN/l)
"wat
er-c
lear
ing
-eff
ect"
of
sub
mer
ged
pla
nts
(%
)
chl-a
turbidity
Tropical climate
-100
-50
0
50
100
0.0 0.1 0.6
Total-N (mgN/l)
"wat
er-c
lear
ing
-eff
ect"
of
sub
mer
ged
pla
nts
(%
)
chl-a
turbidityWater clearing effect of submerged macropytesTropical climate
-100
-50
0
50
100
0.0 0.1 0.6
Total-N (mgN/l)
"wa
ter-
cle
ari
ng
-eff
ec
t" o
f s
ub
me
rge
d p
lan
ts (
%)
chl-a
turbidity
We found a water clearing effect of submerged macropytes along the whole climate gradient
We found a small effect on the TP chl-a relationship
Preliminary results
We did not find submerged macrophytes in more turbid conditions in warmer climates
NWO/WOTRO
The National Geographic Society
The Schure-Beijerinck-Popping fund
Kosten Watersport bv.
Gissell Lacerot
Andy LotterBart KoelmansCarla KrukChristina Branco David da Motta MarquesErik JeppesenEgbert van NesFabio Roland Jeroen de Klein John BeijerJose Luiz AttaydeJose PaggiKatleen van der GuchtLuc de MeesterMarten Scheffer Miquel LurlingNestor MazzeoSusana de PaggiVera Huszar
www.salga.wur.nl