Abstract
During summer of 2001, venous blood gases were determined in loggerhead sea turtles (Caretta caretta) captured by trawl in coastal waters of South Carolina and Georgia as part of a sea turtle census program (n = 16), and captured in pound nets in coastal North Carolina for subsequent laboratory based orientation investigations (n = 6). Trawls were towed for 30 minutes, so turtles captured were forcibly submerged for 30 minutes or less. Pound nets are passive gear in which fish (and sea turtles) are funneled into a concentrated area and removed periodically (3 times weekly in this case). Sea turtles in pound nets are free to surface and to feed at will. Blood was obtained from the dorsal cervical sinus as quickly as possible after landing on the boat (range 2-10 minutes trawl, 1-2 minutes pound net) and at 30 minutes after landing just prior to release. Blood gases were determined within 10 minutes of sampling on an iStat portable clinical analyzer (Heska Corporation, Fort Collins, Colorado, USA) using CG4+ cartridges. Parameters measured included pH, pO2, pCO2, and lactate. Instrument measurements for pH, pO2, and pCO2 made at 37 °C were corrected to cloacal temperature manually in preference to automatic iStat human-based algorithms (Table 1), and HCO3-was calculated from temperature corrected pH and pCO2.1-3 Comparing pound net and trawl captures, venous blood pH and bicarbonate were higher, and pO2 and lactate were lower from pound net turtles at the initial sampling time. In pound net turtles, pH and bicarbonate declined and lactate increased during the 30 minutes on deck. In trawled sea turtles venous blood pH increased and pCO2 and pO2 decreased during the 30 minutes on deck.
Table 1. Directly measured 37°C and temperature corrected median [lower quartile, upper quartile] values for venous pH, PvCO2 and PvO2 from loggerheads sampled initially (T0) and 30 minutes (T30) after capture by pound net or trawl.
|
|
pH
|
pH
|
PvCO2
|
PvCO2
|
PvO2
|
PvO2
|
|
37°C
|
corrected
|
37°C
|
corrected
|
37°C
|
corrected
|
|
Pound
|
7.22
|
7.35
|
90.9
|
61.9
|
72.0
|
64.0
|
|
T0
|
[7.14, 7.28]
|
[7.27, 7.40]
|
[77.7, 108.3]
|
[52.2, 70.5]
|
[67.2, 82.8]
|
[59.5, 73.2]
|
|
Pound
|
7.24
|
7.35
|
62.3
|
42.8
|
75.5
|
66.5
|
|
T30
|
[7.13, 7.26]
|
[7.27, 7.38]
|
[60.5, 66.2]
|
[41.4, 47.4]
|
[70.5, 88.8]
|
[63.5, 78.5]
|
|
Trawl
|
7.02
|
7.16
|
76.6
|
62.95
|
93.5
|
83.0
|
|
T0
|
[6.97, 7.12]
|
[7.08, 7.24]
|
[69.0, 97.6]
|
[54.7, 85.7]
|
[87.0, 104.8]
|
[77, 93.2]
|
|
Trawl
|
7.13
|
7.25
|
52.2
|
35.2
|
80.0
|
70.5
|
|
T30
|
[7.07, 7.23]
|
[7.20, 7.34]
|
[47.3, 56.7]
|
[32.4, 38.3]
|
[75.2, 92.8]
|
[67.2, 82]
|
Acknowledgements
We thank David Whitaker, Bruce Stender, Joanne McNeill, Larisa Avens, Steve Searcy, Kyra Tehve-Swallow, Cliff Swanson, William Horne, Greg Lewbart, Beth Chittick, and the crews of the trawlers and pound nets. This project was supported by the South Carolina Department of Natural Resources and the state of North Carolina.
References
1. Ashwood ER, G Kost, M Kenney. 1993. Temperature correction of blood-gas and pH measurements. Clinical Chemistry 29:1877-1885.
2. Kraus DR, DC Jackson. 1980. Temperature effects on ventilation and acid-base balance of the green turtle. American Journal of Physiology 239:254-258.
3. Stabenau EK, TA Heming. 1993. Determination of the constants of the Henderson-Hasselbalch equation, aCO2 and pKa, in sea turtle plasma. Journal of Experimental Biology 180:311-314.