Hawkesbury-Nepean River Environmental Monitoring Program

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also indicated significant differences among each of the decades when compared with one another (ANOSIM; P = 0.001). The results for the 1970s however, may require some degree of caution in interpretation, since only eight samples were available at N26 during the 1970s. SIMPER (Clarke and Gorley 2006) was used to identify which genera contributed the most to the significant differences among decades. This information is summarised in Table A8.1 (Appendix 8). For the 2000s decade samples the most distinguishing factor is an increase in occurrence and density of Aphanocapsa (Figure 6.26). Aphanocapsa was not recorded at N26 before August 1999, but it is now the dominant genus in the algal community, being responsible for many recent blooms (up to 1 138 807 cells/mL on 19/12/03). Other genera contributing to the observed differences among decades include Microcystis (much higher average abundances in the 1980s and 1990s than in the 2000s); Aphanothece (much higher average abundances in the 1990s than in the 2000s or 1980s); Cyanodictyon (not recorded at N26 in the 1970s, 1980s or 1990s, but averaging 55 716 cells/mL in the 2000s); Anabaena (much higher average abundances in the 1980s and 1990s than in the 2000s); and Skeletonema (much higher average abundances in the 1980s than in the 1990s or 2000s). Other genera at times showed peaks in occurrence at various times but did not contribute as much to the dissimilarity among decades as these five genera. What does seem apparent is that the blue-green algal component of aquatic flora of the Hawkesbury River at Sackville is now quite different from what was there throughout the 1980s and 1990s, with Aphanocapsa and Cyanodictyon replacing Anabaena and Microcystis as the dominant blue-green-algal genera. Figure 6.25: Multidimensional scaling ordination identifying decadal differences in algal communities at Sackville (N26) 54 Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report
Figure 6.26: Temporal differences in cyanobacterial counts at Sackville (N26) If the algal data at N26 are divided into different seasons (summer, autumn, winter and spring) then the differences are less clear cut (Figure 6.27) but still significantly different from one another (ANOSIM, P = 0.001). Pair-wise comparison of seasons also indicated significant differences among each of the seasons when compared with one another (ANOSIM, P = 0.001 to P = 0.021). These putative seasonal differences are dominated by Microcystis (more abundant in summer), Aphanocapsa (more abundant in summer, autumn and winter than spring), Aphanothece (more abundant in summer and, to a lesser extent, winter), Anabaena (more abundant in summer) and Skeletonema (more abundant in winter). If just the more recent data for the 2000s decade are considered, however, no significant difference among seasons can be determined (ANOSIM, P = 0.083; Figure 6.27). This may be affected to some degree by the lower number of samples and the fact that, at N26, algal and cyanobacterial counts are conducted only if chlorophyll-a levels are above 10 µg/L. Hawkesbury River – North Richmond (N42). If the algal data at N42 are divided into the various decades, then clear differences are again distinguishable (Figure 6.28), particularly for algal samples taken more recently (2000s decade). This analysis was based on genus-level differences rather than species-level differences, since taxonomic resolution has varied over time. Bray-Curtis similarity matrices were calculated using the raw (untransformed) data. These analyses indicated significant differences among decades in terms of the genus-level composition of algae in the Hawkesbury-Nepean River (ANOSIM, P = 0.001). Pair-wise comparison of decades also indicated significant differences among each of the decades when compared with one another (ANOSIM, P = 0.001). The results for the 1970s should be more reliable at this site, since 120 samples were available at N42 throughout the 1970s. SIMPER (Clarke and Gorley 2006) was used to identify which genera contributed the most to the significant differences among decades. This information is summarised in Table A8.2 (Appendix 8). Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report 55
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Hawkesbury-Nepean River Environment
Page 3 and 4:
CONTENTS: BOOKLET Summary..........
Page 5 and 6:
Summary Adaptive management require
Page 7 and 8:
1. Introduction The Hawkesbury-Nepe
Page 9 and 10: • local government • other stak
Page 11 and 12: Sackville that have been the site o
Page 13 and 14: Long-term monitoring sites A review
Page 15 and 16: including algal blooms. This presen
Page 17 and 18: Figure 5.1: Long-term sampling site
Page 19 and 20: General observations from these gra
Page 21 and 22: Figure 5.4: Smoothed trend lines fo
Page 23 and 24: are also highly variable in terms o
Page 25 and 26: Water quality trends using statisti
Page 27 and 28: Figure 5.9: Chlorophyll-a levels ov
Page 29 and 30: al. (1999, 2004). Sydney Water rout
Page 31 and 32: N95 Edge Samples N95 Riffle Samples
Page 33 and 34: quality and macroinvertebrate commu
Page 35 and 36: Figure 6.6: Principal components an
Page 37 and 38: Figure 6.8: Average SIGNAL-SG score
Page 39 and 40: Sites upstream and downstream of da
Page 41 and 42: Figure 6.10: Multidimensional scali
Page 43 and 44: Temporal trends in AusRIVAS-based a
Page 45 and 46: Trends in periphytic diatom communi
Page 47 and 48: species did not appear in searches
Page 49 and 50: the average percentage abundances (
Page 53 and 54: . Figure 6.18: Sampling sites for f
Page 55 and 56: Hypseleotris were caught only much
Page 57 and 58: Figure 6.23: Length frequencies of
Page 59: Figure 6.24: Chlorophyll-a, total c
Page 65 and 66: Figure 6.30: Temporal differences i
Page 67 and 68: (e.g. Merismopedia, Phormidium) hav
Page 69 and 70: Macrophytes Large aquatic plants pl
Page 71 and 72: • Two species of weeds, Gymnocoro
Page 73 and 74: ecord for the unregulated Colo Rive
Page 75 and 76: River has changed in the recent pas
Page 77 and 78: Maheshwari B.L., Walker K.F. and Mc
Page 79 and 80: Department of Environment and Clima
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Hawkesbury-Nepean River Environmental Monitoring Program

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