physical processes in a mesophotic coral refuge across bleaching events joanna gyory 1 · tyler...
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Physical processes in a mesophotic coral refuge across bleaching events
Joanna Gyory1 · Tyler Smith1 · Laurent Cherubin2
1University of the Virgin Islands2University of Miami
27.5 28.0 28.5 29.0 29.5 30.0 30.5
0
20
40
60
80
100
120
Number ofDays at orAbove eachTemperature
Temperature (oC)
1990 1991 1992 1993 1994 1995 1996 1997 1998 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Shallow water temperature has increased in the past two decades in the USVI
Shallow water temperature has increasedin the past two decades in the USVI
• Computed daily average temperature between July 1 and October 31
• Counted the number of days at or above each temperature for each year
27.5 28.0 28.5 29.0 29.5 30.0 30.5
0
20
40
60
80
100
120
Number ofDays at orAbove eachTemperature
Temperature (oC)
1996
116
26
0
27.5 28.0 28.5 29.0 29.5 30.0 30.5
0
20
40
60
80
100
120
Number ofDays at orAbove eachTemperature
Temperature (oC)
1990 1991 1992 1993 1994 1995 1996 1997 1998 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Shallow water temperature has increased in the past two decades in the USVI
Shallow water temperature has increasedin the past two decades in the USVI
BleachingPrevalence
Photo by Robert Brewer
Temperature
Irradiance
Potential for heterotrophy
90
70
50
30
10
0 400 800 1200 1600
Photosynthetically Active Radiation (E m-2 s-1)
Depth (m)
90
70
50
30
10
0 400 800 1200 1600
Photosynthetically Active Radiation (E m-2 s-1)
Depth (m)
22%
90
70
50
30
10
0 400 800 1200 1600
Photosynthetically Active Radiation (E m-2 s-1)
Depth (m)
22%
9%
90
70
50
30
10
0 400 800 1200 1600
Photosynthetically Active Radiation (E m-2 s-1)
Depth (m)
22%
9%
3%
Photo by Robert Brewer
Temperature
Irradiance
Potential for heterotrophy
Shallow
Mesophotic
0 5 10 15 20100
80
60
40
20
0
Depth (m)
Distance along transect (Km)
Shallow (9 m)
Mesophotic(37 m)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
26
27
28
29
30
Mesophotic
Temperature
(oC)
2007
Shallow
Bleachingthreshold
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec25
26
27
28
29
30
Mesophotic
Shallow
Temperature
(oC)
2008
Bleachingthreshold
80
70
60
50
40
30
20
10
027.5 28.0 28.5 29.0
Temperature (oC)
Dep
th (
m)
36.2 36.4 36.6
Salinity (PSU)
Winter Summer
80
70
60
50
40
30
20
10
026.0 26.5 27.0
Temperature (oC)
Dep
th (
m)
35.0 35.5 36.0 36.5 37.0 37.5 38.0
Salinity (PSU)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec25
26
27
28
29
30
Mesophotic
Shallow
Temperature
(oC)
2008
Bleachingthreshold
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec25
26
27
28
29
30
31
Mesophotic
Shallow
Temperature
(oC)
2010
Bleachingthreshold
Jul 27 Jul 28 Jul 29 Jul 30 Jul 31 Aug 1 Aug 2 Aug 326
27
28
29
30
Mesophotic
Shallow
Temperature
(oC)
2010
Hurricane Earl
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
25
26
27
28
29
30
31
Mesophotic
Shallow
Temperature
(oC)
2010
Mar Apr May Jun Jul Aug Sep Oct Nov Dec25
26
27
28
29
30
31
thresholdBleaching
37 m
Temperature
(oC)
2005
9 mShallow
Mesophotic
Mar Apr May Jun Jul Aug Sep Oct Nov Dec25
26
27
28
29
30
31
9 m
Temperature
(oC)
2005
37 m
Bleaching
threshold
Shallow
Mesophotic
Mar Apr May Jun Jul Aug Sep Oct Nov25
26
27
28
29
30
31T
em
pe
ratu
re (
oC
)
Bleaching
threshold
200520102008
Daily average temperature in a mesophotic reef
Photo by Robert Brewer
Temperature
Irradiance
Potential for heterotrophy
Mar Apr May Jun Jul Aug Sep Oct Nov
80
100
120
140
Backscatter(counts)
2005
Backscatter strength above a mesophotic reef
120
100
80
60
40
20
0
0.0 0.4 0.8 1.2 1.6
Chlorophyll (mg m-3)
Depth (m)
Nov-Mar2006-2011
120
100
80
60
40
20
0
0.0 0.4 0.8 1.2 1.6
Apr-Oct2006-2011
Chlorophyll (mg m-3)
Mar Apr May Jun Jul Aug Sep Oct Nov
80
100
120
140
Backscatter(counts)
2005
Backscatter strength above a mesophotic reef
Mar Apr May Jun Jul Aug Sep Oct Nov60
80
100
120
140
Backscatter strength above a mesophotic reef
Backscatter(counts)
2006
Mar Apr May Jun Jul Aug Sep Oct Nov
80
100
120
140
Backscatter strength above a mesophotic reef
Backscatter(counts)
2007
Mar Apr May Jun Jul Aug Sep Oct Nov
60
80
100
120
140
Backscatter strength above a mesophotic reef
Backscatter(counts)
2008
2005 2006
2007 2008
Conclusions
• Seasonal stratification separates the environments of shallow and mesophotic reefs
• Mesophotic corals have a different bleaching threshold than shallow corals
• Hurricane mixing may increase temperature in the mesophotic environment
• Hints that zooplankton delivery to mesophotic reefs is enhanced during warmest months
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec25
26
27
28
29
30
Mesophotic
Shallow
Temperature
(oC)
2008
Bleachingthreshold
Mar Apr May Jun Jul Aug Sep Oct Nov Dec25
26
27
28
29
30
31
9 m
Temperature
(oC)
2005
37 m
Bleaching
threshold
Hurricane Earl
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
25
26
27
28
29
30
31
Mesophotic
Shallow
Temperature
(oC)
2010
Mar Apr May Jun Jul Aug Sep Oct Nov
80
100
120
140
Backscatter(counts)
2005
Backscatter strength above a mesophotic reef