Changes in these candidates were investigated along a well-defined water quality gradient (a composite index of 13 water quality variables, see below) in one geographic region (the Whitsunday Islands, central GBR; Cooper et al., 2007), and again,
to assess consistency, on three reefs in each of four GBR inshore regions along well-defined water quality gradients (defined as changes in turbidity and chlorophyll) away from the mouths of major rivers (Schaffelke et al., 2012).