Stable Isotopes of Pteropod Shells as Recorders of Sub-Surface Water Conditions
201
G. ruber(w)
L. inflata
diff.(meas-G.r.) dlff.(meas-L.i.)
Year
season
meas. SST
calc. SST
calc. SST
°C
°C
°C
°C
°C
1988 winter
19.9
spring
20.5
19.5
1.0
summer
23.8
27.3
21.6
-3.5
2.2
fall
22.5
25.4
21.2
-2.9
1.3
annual mean
21.7
26.4
20.8
-4.7
0.9
1989 winter
19.4
21.3
19.4
-1.9
0.0
spring
20.1
21.7
20.6
-1.6
-0.5
summer
24.6
24.7
22.9
-0.1
1.7
fall
22.8
25.0
22.9
-2.2
-0.1
annual mean
21.7
23.2
21.5
-1.5
0.3
1990 winter
20.2
21.1
19.9
-0.9
0.3
spring
20.8
21.3
20.2
-0.5
0.6
summer
24.4
23.0
20.8
1.4
3.6
fall
22.5
24.8
21.7
-2.3
0.8
annual mean
22.0
22.6
20.7
-0.6
1.3
1991 winter
19.8
21.7
19.8
-1.9
0.0
spring
20.2
summer
23.0
21.8
20.8
1.2
2.2
fall
23.3
21.7
1.6
annual mean
21.6
21.8
20.8
-0.2
0.8
4-yearmean
21.8
23.5
21.0
-1.7
0.8
Table 2. Measured and calculated (G. ruber, L. inflata) seasonal temperatures and annual means (calculated from
the seasonal means) off Cape Blanc. Deviations from the measured SSTs are also shown.
Yet, it can provide only a sensitivity of ±1.6°C
(Grossman and Ku 1986).
If such SST-oI3C relationship should become
observable, a correlation between 0 18 0 and Ol3C
of L. injlata should be observed (see Jasper and
Deuser 1993). This relationship is plotted in Fig. Sa.
We obtained two different clusters whereby L.
injlata shows a weak positive 0180_013C - relationship, suggesting a negative temperature dependency. The correlation coefficient (R2), however,
is only 0.22 (N=54) for the lower trap samples. Almost similar ranges in 8 18 0 and 8 l3 C and relationships between them were stated by Jasper and
Deuser (1993) for several migratory species. In
Fig. 5b, we plotted calculated temperatures from
the 0 18 0 record versus the OI3C values and obtained a slightly lower slope (013C = -0.08 T + 2.9;
R2=0.26; N=54) compared to Grossman and Ku
(1986: Ol3C = -0.11 T + 2.4). As expected, we have
no indication for such a temperature change pro-
201
G. ruber(w)
L. inflata
diff.(meas-G.r.) dlff.(meas-L.i.)
Year
season
meas. SST
calc. SST
calc. SST
°C
°C
°C
°C
°C
1988 winter
19.9
spring
20.5
19.5
1.0
summer
23.8
27.3
21.6
-3.5
2.2
fall
22.5
25.4
21.2
-2.9
1.3
annual mean
21.7
26.4
20.8
-4.7
0.9
1989 winter
19.4
21.3
19.4
-1.9
0.0
spring
20.1
21.7
20.6
-1.6
-0.5
summer
24.6
24.7
22.9
-0.1
1.7
fall
22.8
25.0
22.9
-2.2
-0.1
annual mean
21.7
23.2
21.5
-1.5
0.3
1990 winter
20.2
21.1
19.9
-0.9
0.3
spring
20.8
21.3
20.2
-0.5
0.6
summer
24.4
23.0
20.8
1.4
3.6
fall
22.5
24.8
21.7
-2.3
0.8
annual mean
22.0
22.6
20.7
-0.6
1.3
1991 winter
19.8
21.7
19.8
-1.9
0.0
spring
20.2
summer
23.0
21.8
20.8
1.2
2.2
fall
23.3
21.7
1.6
annual mean
21.6
21.8
20.8
-0.2
0.8
4-yearmean
21.8
23.5
21.0
-1.7
0.8
Table 2. Measured and calculated (G. ruber, L. inflata) seasonal temperatures and annual means (calculated from
the seasonal means) off Cape Blanc. Deviations from the measured SSTs are also shown.
Yet, it can provide only a sensitivity of ±1.6°C
(Grossman and Ku 1986).
If such SST-oI3C relationship should become
observable, a correlation between 0 18 0 and Ol3C
of L. injlata should be observed (see Jasper and
Deuser 1993). This relationship is plotted in Fig. Sa.
We obtained two different clusters whereby L.
injlata shows a weak positive 0180_013C - relationship, suggesting a negative temperature dependency. The correlation coefficient (R2), however,
is only 0.22 (N=54) for the lower trap samples. Almost similar ranges in 8 18 0 and 8 l3 C and relationships between them were stated by Jasper and
Deuser (1993) for several migratory species. In
Fig. 5b, we plotted calculated temperatures from
the 0 18 0 record versus the OI3C values and obtained a slightly lower slope (013C = -0.08 T + 2.9;
R2=0.26; N=54) compared to Grossman and Ku
(1986: Ol3C = -0.11 T + 2.4). As expected, we have
no indication for such a temperature change pro-