Pooling of samples in proteomics experiments might help overcome resource constraints when many individuals are analysed. The measured biological variation should be reduced giving increased power to detect treatment differences. Pooling has been advocated in microarray work but there are few tests of its potential in proteomics. In this study, we examine three issues on which the success of the pooling approach might hinge and provide evidence that: (i) the protein expression in a pool matches the mean expression of the individuals making up the pool for the majority of proteins, although for some proteins the pool expression is different; (ii) the biological variance between pools is reduced compared with that between individuals, as predicted in theory, but this reduction is not as large as expected. A practical consequence of this is that power could be reduced; (iii) proteins detectable in individual samples are usually but not always visible when samples are pooled. We conclude that pooling of samples in proteomics work is a valid and potentially valuable procedure but consideration should be given to these issues in experimental design.

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25Future oceans are predicted to contain less oxygen than at present. This is because oxygen is 26 less soluble in warmer water and predicted stratification will reduce mixing. Hypoxia in 27 marine environments is thus likely to become more widespread in marine environments and 28 understanding species-responses is important to predicting future impacts on biodiversity. 29This study used a tractable model, the Antarctic clam, Laternula elliptica, which can live for 30 36 years, and has a well characterised ecology and physiology to understand responses to 31 hypoxia and how the effect varied with age. Younger animals had a higher condition index, 32 higher adenylate energy charge and transcriptional profiling indicated that they were 33 physically active in their response to hypoxia, whilst older animals were more sedentary, with 34 higher levels of oxidative damage and apoptosis in the gills. These effects could be attributed,