Journal of the Royal Society of Western Australia, 87(1), March 2004 
Figure 1. Location of macroalgal sampling sites (indicating hard or soft substrate), with estuarine region (lower, mid and upper) 
indicated, in the Swan-Canning Estuary 
Materials and Methods 
Macroalgal communities were sampled every three 
months between August 1995 and May 1997 at 28 
sampling sites (Fig 1). The area of each site was 
approximately 50 m 2 , and they were located near the 
banks of the estuary where water depths were less than 
7 m. Sites were grouped into stratified regions of the 
system, and categorised as the 'lower reaches' (0 to 15 km 
upstream from the estuary mouth), the 'mid reaches' (15 
to 25 km from the mouth), and the 'upper reaches' (25 to 
55 km upstream). 
At each site attached macroalgae were sampled using 
a 0.25 m 2 quadrat, within which all macroalgae were 
removed by hand. Unattached macroalgae were sampled 
using a 9.5 cm (id) perspex corer, which was pushed into 
the sediment over the benthic macroalgae and sealed. 
The macroalgae were then separated from the underlying 
sediment with a 2 mm sieve, and placed on ice. Five 
replicate samples were taken at each site (for both 
quadrats and cores); ten samples at sites where both 
attached and unattached macroalgae were present. 
Macroalgal samples were sorted into species, identified, 
then dried to a constant dry weight at 70-80 °C. Biomass 
estimates are means of 5 replicates, expressed as 
g dry weightin' 2 with associated standard errors. Salinity 
throughout this publication is referred to without units 
according to the Practical Salinity Scale. On this scale, 
salinity is defined as a ratio of conductivities and 
therefore cannot have units. 
Analyses of Variance were performed using Statistica 
for the dependent variables species number and biomass. 
Post-hoc analyses were performed using the Tukey HSD 
test. All data were tested for normality and homogeneity 
of variance prior to analyses; data not normally 
distributed or with homogeneity of variances was log- 
transformed prior to analyses. 
Results and Discussion 
Macroalgal Species 
A list of the macroalgal species recorded during the 
10 
