Evening temperature of natural and artificial nests

Figure 12 Temperature distributions of green turtle C. mydas artificial nests in Pangumbahan beach hatchery A open cage. Measured in the evening at the surface sand and nest upper rim and bottom, mean: 27.4±1.0°C at upper rim nest, 29.6±1.3°C at bottom nest, and 29.7±2.7°C at surface sand. It seems that temperature condition at hatchery was different than at its nature condition, see Figure 11 and 12. Surface sand was warmer than the nest upper rim and bottom part. This condition was contrary to the natural condition which surface sand cooler than at natural nest. Figure 13 Temperature comparisons of green turtle C. mydas natural nests and artificial nests in Pangumbahan beach. Measured in the evening at the surface sand and nest upper rim and bottom. Mean: natural nests: 28.2±0.8°C at upper rim nest, 28.6±0.8°C at bottom nest, 26.7±0.8°C at surface sand; artificial nests 27.2±0.8°C at upper rim nest, 29.6±1.5°C at bottom nest and 30.3±2.5°C at surface sand. 25 26 27 28 29 30 31 32 33 34 5 10 15 20 T e m p e ra tu re ° C artificial nests nest upper rim nest bottom sand surface 25 26 27 28 29 30 31 32 33 34 35 25 26 27 28 29 30 31 32 33 34 35 A r ti fi c ial n e st ° C Natural nest °C nest upper rim nest bottom surface sand Temperature measurement of natural nests n = 9 and artificial nests n = 9 were compared Figure 13. The datasets were distributed normally at the level of significance α = 0.05. Statistically, there were no significance difference between the mean of natural nests and artificial nests temperature at the level significance of α = 0.05 and α = 0.01. Nevertheless, surface sand temperature of natural nests and artificial nests were significantly different at the level of significance α = 0.05 but were not significantly different at the level significance of α = 0.01. It inferred that temperature difference in the natural and artificial nests upper rim and bottom were narrow. But whether it affected hatching success or hatchling sex ratio remain unclear because it was not investigated in this study. Table 11 Sand characteristic at natural nest, artificial nest and hatchery area Sample Sand humidity Dominant sand grain size mm surface bottom note surface bottom Natural nest n = 8 0.7 - 3.7 1.9 ± 1.2 n = 7 0.2 - 4.8 2.7 ± 1.5; n = 7 medium sand - fine sand Artificial nest n = 7 0.3 - 6.6 2.8 ± 2.1 n = 7 0.0 - 7.1 3.0 ± 2.9 n = 7 all at open cage hatchery A fine sand - very find sand medium - fine sand Hatchery Asbestos roof n = 9 0.2 - 11.4 1.9 ± 3.6 n = 9 - very fine - fine sand Hatchery Fiber roof n = 9 0.0 - 7.1 1.5 ± 2.5 n = 9 - very fine - fine sand ∗ Sand humidity was sampled at night. Medium sand :0.50 - 0.25 mm; fine sand: 0.25 - 0.10 mm; very fine sand: 0.10 - 0.05 mm Nest temperature has close relation with its characteristic such as sand humidity and grain size composition. The sampling was taken at dry and wet season. The sand was dry in all samples Table 11. It was not different significantly. Sand composition at natural nest was different to artificial and hatchery. Sand grain provides porosity for interstitial water which can maintain humidity. In turn humidity can decrease temperature. But here we found contrast result. Surface sand of natural nest was cooler than at bottom whereas the surface was drier than the bottom. Surface sand of artificial nest was slightly drier than the bottom, this was in line with temperature condition where surface sand was warmer than the bottom. Humidity is important for hatching. If the sand was too dry then the eggs will not hatch, vise versa, if the sand was to wet then the eggs will become rotten. This is quite an issue in Pangumbahan, especially during dry season. Dry sand tends to be lighter and easy to collapse. It was observed that dry sand hampers the adult female green turtle C. mydas in excavating body pit and eggs cavity while nesting. Dry sand also hampers the hatchlings to emerge to the surface. Thus, Pangumbahan’s wardens gave a lot of effort to maintain the sand humidity at hatchery and beach area. They watered the beach area by seawater and the hatchery by freshwater. The watering at the beach was done every day during dry season before the sun sets. The watering at the hatchery was done every week, especially at the roofed hatchery fiber and asbestos. This strategy was done by experience where many green turtles C. mydas were failed to nest during dry season Janawi, 2010, personal communication. They also experienced of 0 emerging success of green turtle C. mydas hatchlings at fiber roofed hatchery last year. It is inferred that low humidity was the cause of this case. Hence, it is important to monitor sand humidity and temperature for future strategy. In nature, nest depths were ranged around 45 cm until 84 cm depth with 75 of the measurement showed range of approximately 55 – 71 cm Figure 14. Then, the same eggs with mentioned nest depth relocated into hatchery sites. However, all the eggs were not treated resembling the natural condition, regarding the original nest depth. The eggs were reburied into shallower depth nest. The artificial nests were more or less similar in depth. This contrasting nest depth condition caused different pattern of nest bottom temperature between natural and artificial ones. The nest bottom of artificial nest was slightly warmer than the original conditions natural nests. 31 Median 25-75 Non-Outlier Range Outliers natural depth artificial depth 40 45 50 55 60 65 70 75 80 85 D ep th cm Figure 14 Nest depth of green turtle C. mydas natural and artificial nest in cm. Mean = 65.7 ± 10.2 cm natural depth; 50.6 ± 4.3 cm artificial depth

4.1.2.2. Daily sand temperature at hatchery and beach area

Figure 15 Ambient sand temperature at hatchery and beach area of Pangumbahan sampled on November 1 st – 4 th 2011. Note: surface s, subsurface ss; ± 10 cm deep, see Appendix 7a for mean of datasets. Average sand temperature measurement at hatchery and beach area of Pangumbahan were pooled, regardless data grouping according to its environment 20 25 30 35 40 45 50 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 02.00 04.00 Te m p e r atu r e ° C hatchery s hatchery ss beach s beach ss characteristic, such as unshaded area, shaded area and total shade coverage. It presented in Figure 15 above. Range and mean of the measurements are presented in Appendix 10a. Hatchery was warmer than in beach area, at least until approximately 10 cm deep down the surface sand, at all time of this measurement. Surface sand was objected to be influenced by air temperature change. Subsurface sand ± 10 cm depth was cooler than the surface sand at the beginning of daylight and the beginning of dusk and remained until dawn. It was more or less quite stable at all time. It occurred both in hatchery site and beach area. This indicated that the deeper sand could maintain the heat and kept it stable. We observed that adult female green turtles C. mydas excavated sand at least 10 cm deep beneath surface before digging out eggs cavity. Dissimilarity temperature condition between hatchery and beach area was likely to be expected but it is unacceptable for seaturtle embryo development. Nest temperature plays important role in determining hatchlings sex and hatching success. Although nest temperature range may differ by species and region, but in general, higher temperature will produce female individuals Limpus et al., 1985; Miller, 1997. Hatchlings sex ratio skewed toward only in 1 sex, which is female sex, is likely if this condition took place continuously. Hence, it is important to monitor nest temperature and sex ratio estimation at Pangumbahan hatchery. Furthermore, we break down the analysis by its data grouping, according to its environment characteristic, such as unshaded area, shaded area and total shade coverage at hatchery and beach area in order to convince the above result. We compared average of data grouping for surface and subsurface samples. Unshaded samples at hatchery were taken from Hatchery A open cage: A2, A3, A4, and A6 measurement. Shaded samples at hatchery were taken from Hatchery A open cage: A1,A5, A8, A9 and A10 measurement, see Appendix 2a. Total shade coverage by roof at hatchery was taken from hatchery B asbestos roof measurement, see Appendix 2b. Unshaded samples at beach area were taken from US1,U2, U3 and U4 measurement. Shaded samples at beach area were taken from SH1, SH2, SH3 and SH4 measurement. Total shade coverage by vegetation at beach area were taken from VG1, VG2, VG3 and VG4, see Appendix 2c. The result presented in Figure 16 below. Figure 16 Ambient temperature of surface sand at hatchery and beach area in Pangumbahan November 1 st -4 th 2011. Pooled data of hatchery A and B: at unshaded area r = 6, shaded area r = 8 and total shade coverage by roof r =10 at hatchery A open cage and hatchery B asbestos roof, and beach area: at unshaded area r = 4, shaded area r = 4 and total shade coverage by vegetation r = 4, see Appendix 7b for mean of datasets. Ambient sand temperature measurement were taken in three days with interval of 2 hours for each measurement to observe the daily fluctuations. Measurement were started during November 1 st until November 3 rd 2011. Rainfall was quite high during the measurement. Figure 16 showed that the average temperature of surface sand was not significantly different during the beginning of daylight of 6.00 am – 8 am and dusk until dawn 18.00 pm – 04.00 am. Different fluctuation occurred during 10.00 am until 14.00 pm. Ambient temperature at unshaded area in hatchery was the highest. Interestingly, it was only at the hatchery with total covered by roof hatchery B that did not show significant fluctuation. Surface sand of hatchery in unshaded area were much warmer than at the beach area. Surface sand at hatchery and beach area, particulary in the shaded area, were not too different. Obvios difference where seen between surface sand at hatchery B asbestos roof and surface sand under 20 25 30 35 40 45 50 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 02.00 04.00 Time Te m p e r atu r e ° C unshaded hatchery shaded hatchery roof hatchery B unshaded beach shaded beach under veg beach total shade of vegetation coverage at the beach area. Sand subsurface under vegetation at beach area still experienced peak during daylight while sand subsurface at hatchery B asbestos roof did not . Figure 17 Ambient temperature of subsurface sand ± 10 cm depth at hatchery and beach area in Pangumbahan November 1 st -4 th 2011. Pooled data of hatchery A and B: at unshaded area r = 6, shaded area r = 8 and total shade coverage by roof r =10 at hatchery A open cage and hatchery B asbestos roof, and beach area: at unshaded area r = 4, shaded area r = 4 and total shade coverage by vegetation r = 4, see Appendix 7b for mean of datasets. Measurement was taken at deeper sand, approximately 10 cm from surface Figure 17. Fluctuation pattern of subsurface sand temperature was similar to surface sand. It fluctuated during 10.00 am until 14.00 pm and more or less stable at 6.00 am – 8 am and 18.00 pm – 04.00 am but in less range. The warmest temperature was at the unshaded area of hatchery. In general, subsurface sand was more stable than surface sand. This indicated that deeper sand was not influenced greatly by the changing of surface temperature. But intense heat at the surface could induce temperature increase. This shown by sand at unshaded area of hatchery A. Surface temperature was highly influenced by air temperature. Extreme condition at surface sand may also influence temperature at deeper sand. 20 25 30 35 40 45 50 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 02.00 04.00 Time Te m p e r atu r e ° C unshaded hatchery shaded hatchery roof hatchery B unshaded beach shaded beach under veg beach