Methane as a greenhouse gas and food web fuel in some boreal lakes

Methane as a greenhouse gas and
food web fuel in some boreal lakes
Paula Kankaala
University of Eastern Finland, Joensuu
campus, Box 111, FI-80101 Joensuu,
Finland
The results presented here are mainly
from studies at Lammi Biological
Station, University of Helsinki, Finland

Objectives of the studies
• Several projects funded mainly by the
Academy of Finland (from 1991)
– Carbon cycle in boreal lakes, impacts of climate
change
– Lakes as sources and sinks of CO 2 and CH 4
• Littoral and pelagic CH 4 fluxes
• Methanotrophy
• MOB in the diets of crustacean zooplankton of
small stratified lakes (δ 13 C, δ 15 N, PFLA)

Littoral CH 4 emissions were studied in
the vegetated stands of four lakes
Lake Area km 2 TotP µg L -1
Alinen Rautjärvi 0.50 20
Ekojärvi 0.74 22
Pääjärvi 13.4 12
Vesijärvi, Enonselkä 26 36
… and in experimental stands of
Equisetum fluviatile

• CH 4 transport via
aerechymal tissues
• Closed-chamber
technique
• Board-walks in the littoral
zone

…or sampling in a boat

Pelagic area:
Floating chambers and/or measurements of CH 4
concentration in the uppermost 30-cm water layer

Gas samples were analysed with gas chromatograph
equipped with flame ionization detector (FID)

Vegetated littoral areas
100
80
mg CH4 m -2 d -1
60
40
20
0
13/05/2002 12/06/2002 12/07/2002 11/08/2002 10/09/2002 10/10/2002 09/11/2002
Seasonal dynamics of CH 4 efflux (mg m -2 d -1 )
from a Schoenoplectus lacustris stand, Alinen
Rautjärvi

1500
1000
1997
1500
1000
1998
1500
1000
1999
CH4 emission
biomass
500
500
500
0
1-May 1-Jul 1-Sep 1-Nov
0
1-May 1-Jul 1-Sep 1-Nov
0
1-May 1-Jul 1-Sep 1-Nov
Lake Vesijärvi: Efflux of CH 4 (mg m -2 d -1 ) and biomass
of green shoots (g DW m -2 ) in a dense P. australis
stand .

CH 4 effluxes from vegetated littoral stands, mol
CH 4 m -2 (ice-free period) -1
and P. australis
Species
Equisetum
fluviatile
Equisetum
fluviatile
Lake/exp
Sediment
type
LOI
Max
biomass Total efflux Reference
g DW m -2 mol CH 4
m -2
exp.
mesocosm sand 1 ± 0.2 290 ± 70 0.16 Kankaala & Bergström, 2004
exp.
mesocosm silty gyttja 8 ± 0.3 1190 ± 120 2.29 Kankaala & Bergström, 2004
Equisetum
fluviatile Pääjärvi sandy gyttja 8 700 ± 300 2.72 Hyvönen et al. 1998
E. fluv. & P.
australis Ekojärvi silty gyttja 12 ± 4 80 ± 40 0.78 Kankaala et al. 2005
Schoenoplectus
lacustris
Alinen
Rautjärvi
gyttja sand and
Phragmites
australis
P. australis inner
zone
P. australis, outer
zone
Vesijärvi
Scirpus peat 40 ± 35 140 ± 60 0.18 Kankaala et al. 2005
Alinen
Rautjärvi gyttja sand 2 ± 1 70 ± 10 0.22 Kankaala et al. 2005
Phragmites
Vesijärvi peat 85 ± 3 800 ± 100 3.62 Kankaala et al., 2004
Phragmites
peat, 55 ± 5 480 ± 440 7.67 Kankaala et al., 2004
detritus from Lemna trisulca

CH 4 emissions of vegetated
littoral areas
• Seasonal variation correlated with
temperature or plant biomass
(substrate limited areas)
• Between-stand variation correlated with
productivity of CH 4 in the sediment but
not with the sediment organic matter
content

Pelagic zone
In many small boreal lakes the water column is steeply stratified by temperature and oxygen
Incomplete spring
mixing
0.0
Temperature o C
0.0
O 2 mg L -1
-0.5
-0.5
-1.0
-1.0
Depth m
-1.5
-2.0
Depth m
-1.5
-2.0
-2.5
-3.0
-3.5
Mekkojärvi
4
6
8
10
12
14
16
18
20
150 180 210 240 270 300
150 180 210 240 270 300
May Jun Jul Aug Sep Oct May Jun Jul Aug Sep Oct
-2.5
-3.0
-3.5
0
4
6
8
10

The highest CH 4 concentrations are measured in late
summer in the hypolimnion
Depth m
-0.5
-1.0
-1.5
Mekkojärvi
The maximum CH 4
concentrations
measured in the study
lakes varied between
170 and 1900 µmol L -1
-2.0
-2.5
150 180 210 240 270 300
May Jun Jul Aug Sep Oct
20
40
60
80
100
120
140
160

6.0
mmol CH 4 m -2 d -1
5.0
4.0
3.0
2.0
1.0
Chamber
BLD method
0.0
01 April
2002
01 May
2002
01 June
2002
01 July
2002
01 August
2002
31 August
2002
01 October
2002
31 October
2002
The highest CH 4 emissions to the atmosphere
occur during the autumnal turnover period
(Valkea Kotinen)

CH 4 efflux from the pelagic area of the
lakes
CH 4 efflux mol m -2 (ice-free period) -1
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
MJ N AM TL HJ VK OnJ OrJ PJ
Littoral effluxes 0.2 – 7.7 mol CH 4 m -2
(ice-free period) -1
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
R² = 0.758
R² = 0.891
0.001 0.100 10.000
Lake area km 2
No anoxia in
the hypolimnion

Methanotrophy
Littoral area
• Measurements in experimental
stands of Equisetum fluviatile
•

Mekkojärvi 2005
CH 4 efflux or MOB act. mg C -2 d -1
600
500
400
300
200
100
0
01.05.05
01.06.05
MOB activity
Efflux to
atmosphere
02.07.05
02.08.05
02.09.05
03.10.05
03.11.05
mg C m -2 d -1
120
100
80
60
40
20
0
nd
PP
MOB
HBP
GSB
Spring Summer Autumn
Net production by phytoplankton (PP),
heterotrophic bacteria (HBP), methane
oxidizing bacteria (MOB) and green sulphur
bacteria (GBB)
nd

Autumn mixing of the water column
200
-40
150
-50
CH 4 µmol L -1
100
13 C-CH4
-60
-70
50
-80
0
10-Sep 20-Sep 30-Sep 10-Oct 20-Oct 30-Oct
-90
10-Sep 20-Sep 30-Sep 10-Oct 20-Oct 30-Oct
Type I MOB formed 32 ± 23 % of the
bacterial biomass in autumn
0-0.6 m 0.6-1.2 m
1.2-1.8 m 1.8-2.4 m
2.4-3.0 m

Mekkojärvi study in 2005, the diet of
Daphnia longispina
80 %
Algae MOB HB Chlorobium
60 %
40 %
20 %
0 %
Spring Summer Autumn 1 Autumn 2
Additions of NaH 13 CO 3 , corresponding ca. 2‰ of
the amount of total DIC in the epilimnion
Proportions of algae, MOB, HB and GSB in
the diet of Daphnia, IsoSource mixing
model results

Algae and different bacterial groups in the
diets ot crustacean zooplankton in five
lakes
• Lakes with area ranging from 0.003 to 0.145 km 2
• Water colour ranging from ca. 30 to 400 mg Pt L -1
• Sampling in May and October
• Analyses of δ 13 C and 15 N values of cladocerans and
copepods and their potential food sources
• Two-isotope IsoSource modelling of the proportions (%)
of algae, heterotrophic bacteria (HB), green suphur
bacteria (GSB), detritus and methane oxidizing bacteria
(MOB) in the diets of cladocerans and copepods

Two-isotope IsoSource model results of the proportions (%) of
algae, heterotrophic bacteria (HB), green suphur bacteria
(GSB), detritus and methane oxidizing bacteria (MOB) in the
diets of cladocerans and copepods in the five lakes
Cladocera Lake
May
Algae
HB
+GSB+detr MOB
Valkea
Mustajärvi 0-76 23-82 0-17
Valkea
Kotinen 34-86 0-58 7-14
Alinen
Mustajärvi 14-39 60-80 1-6
Nimetön 8-44 39-68 10-24
Mekkojärvi 42-69 19-39 12-19
Copepoda Lake
May
Algae
HB
+GSB+detr MOB
Valkea
Mustajärvi 0-85 15-75 0-28
Valkea
Kotinen 23-28 52-57 17-20
Alinen
Mustajärvi 45-66 9-31 24-25
Nimetön 0-17 53-70 29-35
Mekkojärvi 92-98 2-6 0-2
Oct
Valkea
Mustajärvi 0-21 63-83 15-17
Valkea
Kotinen 38-47 24-35 27-29
Alinen
Mustajärvi 17-26 40-47 34-36
Oct
Valkea
Mustajärvi 4-67 18-71 15-28
Valkea
Kotinen 24-51 41-68 8-12
Alinen
Mustajärvi 61-69 16-23 15-16
Nimetön
no data
Nimetön 0-13 50-64 35-40
Mekkojärvi 20-65 0-32 35-50
Mekkojärvi 0-29 33-53 37-50

Main results and conclusions
• Areal CH 4 effluxes from the vegetated littoral zone are
larger than from the pelagic area of the boreal lakes
- The highest CH 4 effluxes are released from emergent
vegetation stands of eutrophied lakes
- Pelagic CH 4 effluxes are inversely related to the size of the
lake
• In the pelagic area 80-90% of the CH 4 loss is due to
oxidation in the water column
• In small, stratified, boreal lakes (area

Aknowledgements
University of Helsinki:
Jussi Huotari, Tiina Käki, Anne Ojala, Jessica
Linnaluoma, Tiina Tulonen, Elina Peltomaa, Lotta
Lehtinen, Lauri Arvola
University of Jyväskylä:
Roger Jones, Sami Taipale, Hannu Nykänen, Marja
Tiirola
Finnish Environment Institute:
Irina Bergström, Pirkko Kortelainen, Miitta
Rantakari

This presentation is based on the following papers and on some unpublished results
Bergström, I., Mäkelä, S., Kankaala, P. & Kortelainen, P. 2007. Methane efflux from littoral vegetation stands of southern boreal lakes: an upscaled, regional estimate. -
Atm. Env. 41: 339-351.
Hyvönen, T., Ojala, A., Kankaala, P. & Martikainen, P 1998. Methane release from stands of water horsetail (Equisetum fluviatile) in a boreal lake. - Freshwater Biology
40:275-284.
Kankaala, P. & Bergström, I. 2004. Emission and oxidation of methane in Equisetum fluviatile stands growing on organic and sand bottoms. - Biogeochemistry 67: 21-37.
Kankaala, P. Eller, G. & Jones, R.I. 2007. Could bacterivorous zooplankton affect lake pelagic methanotrophic activity? – Fundam. Appl. Limnol. 169: 203-209.
Kankaala, P., Huotari, J., Peltomaa, E. Saloranta T. & Ojala, A. 2006. Methanotrophic activity in relation to methane efflux and total heterotrophic bacterial production in
a stratified, humic, boreal lake. - Limnol. Oceanogr. 51: 1195-1204.
Kankaala, P., Käki, T. & Ojala, A. 2003. Quality of detritus impacts on spatial variation of methane emissions from littoral sediment of a boreal lake. - Arch. Hydrobiol.
157: 47-66.
Kankaala, P., Käki, T., Ojala, A., Pajunen, H. & Arvola, L. 2005. Methane efflux in relation to plant biomass and sediment characteristics in stands of three common
emergent macrophytes in boreal mesoeutrophic lakes. - Global Change Biology 11: 145-153.
Kankaala, P., Mäkelä,S., Bergström, I., Huitu, E., Käki, T. Ojala, A., Rantakari, M. Kortelainen, P & Arvola, L. 2003. Midsummer spatial variation in methane efflux from
stands of littoral vegetation in a boreal meso-eutrophic lake. - Freshwater Biology 48: 1617-1629..
Kankaala, P., Ojala A. & Käki, T. 2004. Temporal and spatial variation in methane emissions from a flooded transgression shore of a boreal lake. - Biogeochemistry 68:
297-311.
Kankaala, P., Taipale, S. Li, L. & Jones, R.I. 2010. Diets of crustacean zooplankton, inferred from stable carbon and nitrogen isotope analyses, in lakes with varying
allochthonous dissolved organic carbon content. – Aquat. Ecol. 44: 781-795.
Kankaala, P., Taipale, S., Grey, J., Sonninen, E., Arvola, L. & Jones, R.I. 2006. Experimental δ 13 C evidence for a contribution of methane to pelagic food webs in lakes. -
Limnol. Oceanogr. 51: 2821-2827.
Kankaala, P., Taipale, S., Nykänen, H. & Jones, R.I. 2007. Oxidation, efflux and isotopic fractionation of methane during autumnal turnover in a polyhumic, boreal lake. -
J. Geophys. Res. 112, G02003, doi: 10.1029/2006JG000336.
Käki, T. Ojala, A. & Kankaala, P. 2001. Diel variation in methane emissions from stands of Phragmites australis (CAV.) TRIN. EX STEUD. and Typha latifolia L. in a boreal
lake.- Aquatic Botany 71:259-271.
López Bellido, J., Tulonen, T, Kankaala, P. & Ojala, A. 2009. CO 2 and CH 4 fluxes during spring and autumn mixing periods in a boreal lake (Pääjärvi, southern Finland). – J.
Geophys. Res. 114, DOI: 10.1029/2009JG000923.
Ojala, A., López Bellido, J., Tulonen, T, Kankaala, P. & Huotari, J. 2011. Carbon gas fluxes from a brown-water and a clear-water lake in the Boreal Zone during a summer
with extreme rain events. – Limnol. Oceanogr. 56: 61-76.
Taipale, S., Kankaala, P. & Jones, R.I. 2007. Contributions of different organic carbon sources to Daphnia in the pelagic food web of a small polyhumic lake: results from
mesocosm DI 13 C-additions. - Ecosystems 10: 757-772.
Taipale, S., Kankaala, P., Hahn, M.W., Jones, R.I. & Tiirola, M. 2011. Methane-oxidizing and photoautotrophic bacteria are major producers in a humic lake with a large
anoxic hypolimnion. - Aquat. Microb. Ecol. DOI:10.3354/ame01512.
Taipale, S., Kankaala, P., Hämäläinen, H., & Jones, R.I. 2009. Seasonal shifts in diet of lake zooplankton revealed by phospholipid fatty acid analysis. - Freshwater Biology
54: 90-104.
Taipale, S., Kankaala, P., Tiirola, M. & Jones, R.I. 2008. Whole-lake dissolved inorganic 13 C additions reveal seasonal shifts in zooplankton diet. – Ecology 89: 463-474.