2.2.2. Study 2
Long-term average turbidity and chlorophyll a data from logging
instruments were used as well as distance to the nearest main
river as an indicator for exposure to terrestrial runoff (Table 1b).
Turbidity and chlorophyll data were obtained from the Reef Rescue
Marine Monitoring Program, using Eco FLNTUSB Combination
Fluorometer and Turbidity loggers (WET Labs, Philomath, USA) deployed
at 5 m depth at each of the 12 study reefs for 12 months
(October 2007–October 2008; see also Schaffelke et al., 2012).
The 10-min data records were averaged over the entire period to
obtain reef-specific long-term mean values for each reef. Mean
long-term turbidity ranged from 0.37 NTU (nephelometric
turbidity units) at Barren Island to 5.05 NTU at Pelican Island.
In all regions, turbidity was highest at the reef nearest to the rivers,
and lowest at the reef furthest from the river (Table 1b). Mean
chlorophyll a concentrations ranged from 0.32 lg L1 at High Island
to 0.72 lg L1 at Pine Island, and differed between regions,
with highest concentrations in the Whitsundays and lowest in
the Wet Tropics region (Table 1b). Chlorophyll a concentrations
declined strongly away from the river in the Keppels region, but
varied non-systematically across stations in the other regions.
Additionally, distinct measurements of Secchi depth and total suspended
solids were available from individual visits (N = 5–8), and
were used for a comparison with data from Study 1.