Hawkesbury-Nepean River Environmental Monitoring Program

quality and macroinvertebrate community composition needs to be undertaken 10
(Figure 6.6)
• individual differences among sites were readily discernible in macroinvertebrate
communities (ANOSIM global test among sites; P = 0.001)
• pair-wise differences among sites were mostly significant (ANOSIM P < 0.05)
with the exception of N26 and N35; N38, N40 and N42; N75 and N80; and N78
and N80.
• yearly differences in macroinvertebrate communities were not as readily
discernible, although still statistically significant (ANOSIM global test among
years, P = 0.006)
• pair-wise differences were mostly non-significant among years (ANOSIM P >
0.05), with the exception of 1994 versus 2003–2006 (P = 0.001 to P = 0.006),
1995 versus 2000–2005 (P = 0.013 to P = 0.024); 1997 versus 2003 and 2005 (P
= 0.036 and P = 0.040, respectively); and 1998 versus 2005 (P = 0.024).
Figure 6.3: Multidimensional scaling ordination of macroinvertebrate samples in the
main-stem of the Hawkesbury-Nepean River, illustrating the difference between edge
and riffle habitats
10 For example, water quality could be averaged over a period of days or months preceding
macroinvertebrate sampling and summarised by using simple univariate statistics (e.g.
medians). However, a significant difficulty arises in defining exactly what the appropriate
period of averaging should be — or indeed the temporal frequency over which
macroinvertebrates may (or may not) be responding to changes in water quality (e.g. the
previous day, week, month, 6 months, year or other time since the last major event).
Further research in this area is warranted.
Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report 27