River and stream water quality and ecology - Greater Wellington ...

River and stream water quality and ecology in the Wellington region: State and trends
catchment (Figure 5.2). There were insufficient data to assess the relationship
between periphyton biomass and urban or exotic forest landcover. However,
all four RSoE sites with a REC landcover class of ‘urban’ were classed as
‘poor’ based on compliance with MfE (2000) periphyton guidelines, while the
single site representing exotic forest landcover was classed as ‘fair’.
Number of sites
25
20
15
10
5
0
Excellent
Good
Fair
Poor
Indigenous forest Pasture Urban Exotic forest
Figure 5.1: Periphyton classes assigned to each of 46 hard-bottomed RSoE sites,
according to the degree of compliance with MfE (2000) guidelines for periphyton
biomass and cover over the period July 2008 to June 2011. Sites are colourcoded
according to their REC landcover class
Mean periphyton biomass (mg chlorophyll a/m 2 )
1000
100
10
1
0.1
REC landcover class
Indigenous forest
Exotic forest
Pastoral
Urban
0 10 20 30 40 50 60 70 80 90 100
% of upstream catchment in indigenous forest landcover
0.1
0 20 30 40 50 60 70 80 90 100
% of upstream catchment in pastoral landcover
Figure 5.2: Scatter plots demonstrating the relationship between mean
periphyton biomass (based on annual sampling in 2009, 2010 and 2011) and the
proportion of indigenous forest (left) and pastoral landcover (right) in the
catchment upstream of each RSoE site. Note that only sites classed as
’pastoral’ (n=17) are included in the pastoral landcover plot
WGN_DOCS-#1100598-V3 PAGE 61 OF 160
Mean periphtyon biomass (mg chlorophyll a/m 2 )
1000
100
10