Changes in algal, coral and fish assemblages along water quality gradients on the inshore Great Barrier Reef

This research was conducted to understand the relationship between water quality and ecological attributes on coral reef communities, through field surveys on naturally turbid inshore coral reefs that vary in exposure to water bourne sediment, nutrient and chlorophyll concentrations. Reefs in two regions were surveyed for biodiversity of algae, hard corals, octocorals and fish. Region PC: Princess Charlotte Bay (in the Claremont Isles, north of PC Bay) and and Region WT: Wet Tropics (between Tully and Port Douglas). SOme reefs were surveyed for the all four groups of taxa, while others were surveyed for some groups of the biodiversity.

Four groups of taxa were surveyed using rapid ecological assessments based on standardized scuba-swims by experts:

1 -macroalgae, mostly identified to genus level

2- hard corals , idenified to species level

3- octocorals, identified to genus level

4 -fish, identified to species or species groups

Abundances of the three benthic groups were rated on a 6-point scale as 0 = ‘absent’, 1 = ‘rare’, 2 = ‘uncommon’, 3 = ‘common’, 4 = ‘abundant’, and 5 = ‘dominant’.

Abundances of some of the fish species were estimated on a log (base 5) scale (Williams, 1982), whereas less abundant fish species were fully enumerated.

Water Quality data was collected between December 2000 and April 2002. Surface water samples were taken at each reef for analysis of 12 water quality variables: particulate nitrogen and phosphorus (PN, PP), nitrate, nitrite, ammonium, total dissolved nitrogen and phosphorus (TDN, TDP), silicate (Sil), chlorophyll (Chl), phaeopigments (Phae), salinity (Sal) and suspended solids (SS).

Analysies included: Redundancy analyses, Permutation tests, Log-linear regression models and Model averaging of models based on the Bayesian Information Criterion was used.