From Fitf. 10.2.1 it can be seen that animals from three of the 

 stations (D, E, F) showed lower respiration rates than animals t rum 

 other stations. This result can, however, be explained by the fact that 

 M. edulis from stations D, E and F were incubated in water with lower 

 oxygen contents than those from the reference station (Table 10.2.1). 

 It is known that low oxygen concentrations depress the respiration of 

 Myt i lus edul is (Bayne, Thompson and Widdows, 1976). 



If the remaining stations (B, C, G) and the reference station (.all 



had about the same oxygen content in the incubation water. Table 10.2.1 ) 



were compared no differences could be found between variances (\ = 



1.93, df = 3) or between means (F .. = 0.85). 



(3: j9) 



The results from the experiment with Myt i lus incubated in water 



with different oil-concentrations (Table 10.2.2) also failed to show 



2 

 statistically significant differences between variances (x = 1.44, df = 



2) or means (F, , = 1.26). 



10.2.3 Conclusions and discussion 



According to this study, oil contamination of the water did not 

 significantly change the respiration of Myti lus edul is . 



However, due to the large variability in respiration, (mean values 

 of approximately 650 |.ig /g/h and standard deviations about 150 pg 0,-,/g/h ) , 

 changes would have had to be large, in order to be detected. To detect, 

 with a probability of 90%, a difference in respiration rate of about 

 20%, the sample size ought to be some 30 specimens (Dixon and Massey 

 1969, Table A-12a). 



10.2.4 References 



Bailey, N.T.J. 1976. Statistical Methods in Biology. 10th ed. Hodder 

 and Stoughton, London. 1-198. 



Bayne, B.L., R.J. Thompson and J. Widdows. 1976. Physiology I. In: 



Bayne, B.L. (ed.). Marine mussels. Their ecology and physiology. 

 Cambridge University Press. Cambridge. 121-206. 



Dixon, W.J. and F.J. Massey. 1969. Introduction to Statistical Analysis. 3rd ed . , 

 McGraw-Hill, Kogakusha, Tokyo, 1-638. 



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