Table 1. Long-term relationship between vibrios and environmental variables in the North Sea.
Set | %Var | Pseudo-F | P | Cum% |
---|---|---|---|---|
(a) Marginal tests, Vibrio abundance vs | ||||
SST | 45.4 | 42.4 | 0.0001 | |
Phytoplankton colour | 33.4 | 25.6 | 0.0002 | |
Total copepods | 20.5 | 13.2 | 0.0004 | |
(b) Sequential tests, Vibrio abundance vs | ||||
SST | 45.4 | 42.4 | 0.0001* | 45.4 |
Total copepods | 4.2 | 4.17 | 0.04* | 50.0 |
Phytoplankton colour | 1.9 | 1.96 | 0.17 | 51.5 |
Abbreviations: Cum%, cumulative percentage of variance explained; SST, sea surface temperature; %Var, percentage of variance in Vibrio data explained by that individual variable.
*P<0.05.
Results of a multiple regression analysis of the Vibrio relative abundance index data versus SST, the phytoplankton colour index and total copepods in the North Sea. Outputs from the analyses include: (a) the results of the marginal tests (that is, fitting each environmental variable individually, ignoring the others), followed by (b) the results of the forward selection procedure with the conditional tests (that is, fitting each environmental variable one at a time, conditional on the variables that are already included in the model). The multiple regressions were based on Euclidean distances calculated among observations from normalised data. The forward selection of the predictor variables was done with tests by permutation. P-values were obtained using 4999 permutations of raw data for the marginal tests (tests of individual variables), whereas for all conditional tests the programme uses 4999 permutations of residuals under the reduced model.