extreme climate events and the recurrent sudden dieback and … · 2012-06-21 · first noticed in...
TRANSCRIPT
CHRISTOPHER M. SWARZENSKI
UNITED STATES GEOLOGICAL SURVEY
LOUISIANA WATER SCIENCE CENTER BATON ROUGE
Extreme Climate Events and the Recurrent Sudden Dieback and Recovery of Salt Marshes in the Rapidly Subsiding Mississippi River Delta, Louisiana
Salt marshes in the Mississippi Delta in coastal Louisiana, rsl is around 1 cm per year
Map from Andrew Tweel, LSU
Mendelssohn and McKee. 1988. Spartina alterniflora die-back in Louisiana: Time-course investigation of soil waterlogging effects. Journal of Ecology 76: 509-521
“Non-acute” salt marsh dieback
Acute saltmarsh dieback
Dieback occurs quickly, from one growing season to next
Full recovery frequently occurs
Occurred in Gulf and Atlantic Coast marshes in 2000s, drought primary driver
Alber, et al. 2008. Salt marsh dieback; An overview of recent events in the US. Estuarine, Coastal and Shelf Science, 80: 1-11.
Acute salt marsh dieback
2000 2006
BACKGROUND
Timeline coastal Louisiana 1999-2009
CLIMATE
Exceptional drought (1999-2000, 2006)
Back to back hurricanes in 2005 and 2008
SALT MARSH DIEBACK
2000 (about 100,000 ha or 25%, widespread)
2009 (smaller area, regional distribution)
0.0
0.1
0.2
0.3
0.4
0.5
MARSH SURFACE
MA
RS
H E
LE
VA
TIO
N O
R
WA
TE
R L
EV
EL I
N M
ET
ER
S AVERAGE
DAILY HIGH
DAILY-AVERAGE WATER LEVEL
Range of marsh elevations with respect to local water levels
% T
IME
MA
RS
H IS
FLO
OD
ED
0
10
20
30
40
50
60
70
Seasonal marsh flooding, related to Gulf level
WA
TE
R L
EV
EL I
N M
ET
ER
S
-0.2
-0.1
0.0
0.1
0.2
Monthly mean sea level (light blue)
MSL
O N D J F M A M J J A S O N D J F M A M J J A S
Level in
feet
-1.0
-0.5
0.0
0.5
1.0
1.5
average 1999-2008
1999-2001
2007-2009
Gulf levels vary from year to year, with long stretches remaining higher or lower than average
Wa
ter
lev
el (
inch
es)
7/15/10 7/19/10 7/23/10 7/27/10 7/31/10
15
20
25
30
35 Open water Marsh water
Microtidal flooding regime, daily flooding alternating with extended periods of drawdown
CU
BIC
CE
NT
IME
TE
RS
x 1
0 3
0
25
50
75
100
Volume of free water greater in low elevation marshes
2000 DIEBACK
F I R S T N O T I C E D I N M A R C H / A P R I L , P O S S I B L E T H A T D I E B A C K O C C U R R E D A F T E R N E W G R O W T H F I R S T S T A R T E D
D I E B A C K L I N K E D T O D R O U G H T
O X I C S O I L S - > P H D R O P - > R E L E A S E O F M E T A L S T O T O X I C C O N C E N T R A T I O N S
McKee et al. 2004. Acute salt marsh dieback in the Mississippi River deltaic plain: a drought-induced phenomenon? Global Ecology and Biogeography 13(1) p.65-73
Dieback in interior areas Spartina alterniflora died back, Juncus roemerianus survived. Where both survived J. roemerianus taller than S. alt where both survived
2000 Dieback (widespread across elevation gradient)
(photo Karen Mckee, USGS)
Typical layout of study site
STUDY DESIGN developed to assess field conditions post-2000 dieback
- Locate paired interior dieback and surviving marshes (N=4) replicate high and low marshes - In field: compare relative elevations, soil salinity, drawdowns, specific yield - In lab: soil acidification potential, metal release
Comparisons at paired interior marshes
High B High A Low B Low A
Parameter live dead live dead live dead live dead
Relative Elevation (cm) + 3 + 5 +3 +3
Monthly Marsh flooding (%) 21 26 13 21 47 41 40 46
Maximum Drawdown (cm) 12 13.5 14 25 5 14 9 12
Specific Yield 0.03 0.08 0.03 0.03 0.09 0.10 0.18 0.17
Acidification Potential 2.6 2.8 2.9 3.2 n.s n.s 4.5 3.3
Average Soil
Salinity (ppt) 17.9 15.9 30.6 27.9 17.2 18.6 19.1 19.4
WA
TE
R L
EV
EL I
N M
ET
ER
S
-0.1
0.0
0.1
0.2
0.3 Low A Low B
-0.1
0.0
0.1
0.2
0.3
Jan
1
Jan
15
Ja
n 2
9
Feb
12
Feb
26
Ma
r 1
2
-0.1
0.0
0.1
0.2
0.3 High A
-0.1
0.0
0.1
0.2
0.3 High B
Jan
1
Jan
15
Ja
n 2
9
Feb
12
Feb
26
Mar
12
Patterns of drawdown at paired marshes
Low A Low B High A High B
0
50
100
150
200
250
300
LIVE
DEAD
WA
TE
R D
RA
INE
D F
RO
M M
AR
SH
S
UB
SU
RF
AC
E I
N L
ITE
RS
Soil pore space volume during drawdowns
CO
NC
EN
TR
AT
ION
IN
MG
/L
ALUMINUM
pH
2
4
6
8
0
5
10
15
20
25
30
MANGANESE
pH
2
4
6
8
0
1
2
3
4
5
IRON
2
4
6
8
0
10
20
30
40
50
pH
2
4
6
8
0
5
10
15
20
25
30
2
4
6
8
0
1
2
3
4
5
2
4
6
8
0
2
4
6
8
10
2
4
6
8
0
5
10
15
20
25
30
2
4
6
8
0
10
20
30
40
50
2
4
6
8
0
1
2
3
4
5
Soil acidification potential and metal release
High marsh A
High marsh B
Low marsh A
Time Series of Soil Salinity in 10 cm increments (00-02)
1-10 cm
11-20 cm
21-30 cm
31-40 cm
41-50 cm
10
20
30
40
50
60
SA
LIN
ITY
IN
PA
RT
S P
ER
TH
OU
SA
ND
6/1
/00
10
/1/0
0
2/1
/01
6/1
/01
10
/1/0
1
2/1
/02
6/1
/02
10
/1/0
2
10
20
30
40
50
60
Surviving marsh Dieback marsh
6/1
/00
10
/1/0
0
2/1
/01
6/1
/01
10
/1/0
1
2/1
/02
6/1
/02
10
/1/0
2
Depth interval
Drought as climate extreme
Key to survival was ability to maintain supply of water during periods of no marsh flooding
In one low elevation area dieback clearly related to soil acidification potential
In remaining three areas (high and low marsh) soil acidification and/or bound water combined with high soil salinity likely contributed to plant mortality
March 5, 2002 October 24, 2003
May 2006
Low Marsh A dieback site recovery; recovery by seedlings at all sites
F I R S T N O T I C E D I N F E B R U A R Y 2 0 0 9 , B E F O R E N E W G R O W T H
2009 Dieback
Dieback in interior areas S. alterniflora and Juncus roemerianus died back J. roemerianus no taller than S. alt where both survived
2009 dieback: limited to low elevation marsh
Hourly waterlevel at Grand Isle, August-October 2005 and 2008(Data from National Ocean Survey)
15-Aug-05
29-Aug-05
12-Sep-05
26-Sep-05
10-Oct-0
5
FE
ET
ME
AN
SE
A L
EV
EL
-2
-1
0
1
2
3
4
5
6
2008
2005
Katrina
Gustav Ike
Rita
In 2005 hurricanes were spaced further apart and base water levels may have been a bit lower
Calculated % time flooded at indicated depths (cm)
>2.5 >7.5 >12.5 >17.5 >22.5 >27.5 >32.5 1 Aug- 31 Oct High marsh A
41 32 24 17 12 9 7 Low Marsh A 62 52 41 31 22 17 12 Sept 1-Oct 16 HM A 63 51 39 32 22 17 13
LM A 80 71 59 56 37 30 22
Patterns of dieback
Within both low marsh sites, areas at about 18-20 cm NAVD88 elevation died back; areas > 24 cm NAVD88 survived; measurements made after dieback occurred
Lake Felicity brown
1/1/09
7/1/09
1/1/10
7/1/10
1/1/11
7/1/11
1/1/12
# s
tem
s p
er
m2
0
50
100
150
200
250
300
number of stems of S. alterniflora per m2 (average of four plots per site)
Lake Felicity green
1/1/09
7/1/09
1/1/10
7/1/10
1/1/11
7/1/11
1/1/12
# s
tem
s p
er
m2
0
50
100
150
200
250
300
Bayou Sale brown
1/1/09
7/1/09
1/1/10
7/1/10
1/1/11
7/1/11
1/1/12
# s
tem
s p
er
m2
0
50
100
150
200
250
300Bayou Sale green
1/1/09
7/1/09
1/1/10
7/1/10
1/1/11
7/1/11
1/1/12
# s
tem
s p
er
m2
0
50
100
150
200
250
300
Stem density of S. alterniflora over time at plots established during 2000 dieback
Recovery at 2009 dieback sites
Storm surge as climate extreme
Dieback restricted to lower elevation marshes
Both S. alterniflora and J. roemerianus affected
Within a site, lowest elevation marshes affected
Wild cards – spacing of storm surge may play a role as may exact storm path
Re-growth 2009 to 2010 at Low marsh A
- D R O U G H T A F F E C T S M A R S H E S W I T H D I F F E R E N T E L E V A T I O N S E Q U A L L Y ; S T O R M S U R G E A F F E C T S L O W L Y I N G M A R S H E S
-C L I M A T E P E R T U R B A T I O N S D O N ’ T A F F E C T P L A N T S P E C I E S E Q U A L L Y
- R E G R O W T H T H R O U G H S E E D L I N G S ( S . A L T E R N I F L O R A )
- U N E X P E C T E D R E S I L I E N C E O F C O A S T A L L O U I S I A N A S A L T M A R S H E S T O C L I M A T E P E R T U R B A T I O N B E F O R E S E A L E V E L R I S E A C C E L E R A T E S
Summary
Healthy Die-Back
HIGH A HIGH B LOW A LOW B
2000 2006 2009 2011
- Tommy Michot, (ICEE, U. Louisiana Lafayette) - Richard Day (USGS-BRD) - Camille Stagg, USGS-BRD -Bob Gambrell (LSU)
MSL
O N D J F M A M J J A S O N D J F M A M J J A S
Level in
feet
-1.0
-0.5
0.0
0.5
1.0
1.5
average 1999-2008
1999-2001
2007-2009
Gulf levels vary from year to year, with long stretches remaining higher or lower than average