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

River and stream water quality and ecology in the Wellington region: State and trends
The MCI developed for hard-bottomed streams was applied to all 55 RSoE
sites, including the nine sites with predominantly soft sedimentary substrate
(see Appendix 1). While this approach differs from some earlier reports
(eg, Perrie 2007; Perrie & Cockeram 2010) that used the MCI developed for
soft-bottomed streams (MCIsb) to summarise data collected from these sites, it
provides for easier inter-site comparisons and avoids some of the uncertainties
and limitations associated with the use of the MCIsb. For example:
Stark and Maxted (2007) note that MCIsb is most appropriate for use at
sites that are known to be naturally soft-sedimentary rather than hardbottomed
sites that have been inundated with sediment. While the natural
substrate characteristics of the nine RSoE sites that have predominantly
soft sedimentary substrate are unknown, at least some of these sites are
likely to have been hard sedimentary in their natural state.
A number of taxa recorded at soft-bottomed RSoE sites have yet to be
assigned MCIsb tolerance scores, meaning that the index can only be
calculated from a subset of the total taxa present.
Relationships between macroinvertebrate metrics, landcover and selected
environmental variables were assessed using Spearman rank correlations with a
significance threshold of p