Hawkesbury-Nepean River Environmental Monitoring Program

Figure 6.31: Multidimensional scaling ordination indicating seasonal patterns of algal
communities at North Richmond, Site N42: all data (top); 2000s data only (bottom)
Comparisons between Sackville (N26) and North Richmond (N42). Although
there are many similarities in the algal communities at N42 and N26, there are also
some important differences. Throughout the 1980s, when Anabaena was blooming at
N42, it was also blooming at N26 (Figure 6.32). However, in the 1990s, Anabaena
bloom formations at N26 were not accompanied by blooms of similar magnitude at
N42. In contrast, when Microcystis was blooming at N26 it was occasionally blooming
at N42 but with much lower cell counts (Figure 6.32). More recently, Aphanocapsa
blooms have occurred at both N42 and N26, but cell counts have been much higher
at N26 (Figure 6.32). In the past, significant blooms of some cyanobacterial genera
60 Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report