Diapositive 1 - de l'Université libre de Bruxelles

Chapitre IIIindividual variation was responsible for 43% of the variation with CI 95 ranging between90–98 and 94–115 mmol/mol, i.e., 8%–22% of the mean, according to the consideredconditions. It is noteworthy that the Mg/Ca versus salinity relationships differedaccording to temperature (Figure 24).Table 12: Statistical results of the stepwise multiple regressions between Mg/Ca and Sr/Ca ratios inthe newly formed skeleton and possible dependent variables.Mg/CaSr/Ca1 st variable 2 nd variable 3 rd variable R 2 Sign. of additional variableSalinity 0.25 < 10 -5Salinity Temperature 0.57 < 10 -5Salinity Temperature Growth rate 0.57 0.7Salinity Temperature Size 0.57 0.8Salinity 0.70 < 10 -5Salinity Temperature 0.86 < 10 -5Salinity Temperature Growth rate 0.86 0.7Salinity Temperature Size 0.86 0.9120Skeletal Mg/Ca (mmol/mol)1101009080y = 1.6898x + 51.6829R 2 = 0.685; p = 2.2 10-5y = 0.9443x + 65.4850R 2 = 0.395; p = 7 10-57020 25 30 35 40Salinity (psu)Salinity (psu)Figure 24: Mg/Ca ratio (mmol/mol) in the skeleton of Asterias rubens grown in aquarium accordingto salinity and temperature of growth (———11°C;---------18°C ); equations and parameters of thelinear regressions at each temperature (———11°C;---------18°C).The Sr/Ca ratio was highly dependent on salinity, the latter explaining 70% of thevariation, temperature accounting for a further 16% (Table 12). Sr/Ca ratios versussalinity relations did not differ according to temperature (Figure 25). Individual variationin Sr/Ca was lower, with CI 95 ranging from 2.18–2.26 to 2.25–2.42 mmol/mol, i.e., 4%–7% of the mean.68