Of primary interest were major seasonal differences in the effect of location and distance. Two seasons were considered,

nominally referred to here as winter and summer reflecting water temperature (less than 10 °C and more than 10 °C respectively). Season was, therefore, also considered fixed. For each sampling time (Month) two individual reef modules from each group of six (Group) were randomly selected. Avasimibe nmr At each reef-distance 10 redox measurements were taken, the locations of which were randomly allocated by the diver swimming for a pre-selected random time of between 1 and 15 s around the reef perimeter (0 m stations) or guided to 1 and 4 m stations using a marked rope. The objective was to take 180 measurements per time interval (3 groups, 2 modules from each group, 30 readings per module). However, during periods of poor weather this sampling programme was not completed and the following numbers of modules per group (A, B and D) were measured on the following dates: March 2005 A: zero, B: one and D: two; September 2005 A: zero, B: one and D: one and October 2005 A: two, B: one and find more D: one. At all other occasions the full sampling programme was achieved.

Two dives were permissible per day resulting in a minimum of three consecutive days to visit the six modules (two modules on each of three groups). During poor weather the period over which a single time-period’s data were collected was extended up to seven days. These data were considered to represent one time period. Visual assessments of the reefs and the surrounding environment were made, particularly in reference to any accumulations of organic material and the nature of the sediment. The bottom-water temperature was recorded using an integral old depth gauge and thermometer during each dive. The mean temperature for each month is reported. Pre-analysis data exploration (checking outliers, homogeneity, normality) followed the protocol of Zuur et al. (2010). Model development and selection in mixed models can be relatively complex (and iterative) and the guidance given in Zuur et al. (2009), detailed

below, was followed: 1. The beyond optimal (all fixed effects and interactions) model was initially fitted using generalised least-squares regression and the residuals examined for homoscedasticity. If any residual trends were identified a range of variance structures were tested and compared on the basis of their Akaike information criteria (AIC) score (where the lowest AIC was considered the optimal model). The goal was to identify, and allow for, differences in variance as a function of either one or more categorical predictors. Residuals from the model with the lowest AIC were reassessed to check that any heteroscedasticity had been incorporated into the model. All model predictions, and 95% confidence intervals (shown graphically) relate only to the fixed factors.