New Zealand Journal of Marine and Freshwater Research abstracts
A biotic index for New Zealand's soft-bottomed streams
John D. Stark
Cawthron Institute
Private Bag 2
Nelson, New Zealand
email: john.stark@cawthron.org.nz
John R. Maxted*
Auckland Regional Council
Auckland, New Zealand
*Present address: South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, Florida, United States.
Abstract Versions of the Macroinvertebrate Community
Index (MCI) and its semi-quantitative (SQMCI) and quantitative (QMCI)
variants used extensively in New Zealand to assess organic pollution in
hard-bottomed (HB) streams have been developed for assessing the health
of soft-bottomed (SB) streams dominated by fine sediments, woody
debris, and macrophytes. An iterative rank correlation procedure
developed in Australia was used to derive tolerance values for 124
macroinvertebrate taxa using a data set of 224 samples from 50 sites in
the Auckland region. Deriving SB tolerance values to the nearest 0.1
(range 0.1—10.0) improved index performance and eliminated confusion
with the integer tolerance values of the HB indices. The new indices
(MCI-sb and SQMCI-sb), exhibited a greater range of scores overall and
across gradients of forestry, rural, and urban land-use intensity
compared to the MCI and SQMCI when applied to SB streams. Higher scores
for reference sites, lower scores for severely degraded sites, and high
rank correlations (rs) with environmental variables, including % developed land in the catchment (rs = —0.842), a water quality index (rs = 0.818), and a habitat quality index (rs
= 0.648), confirmed the superiority of MCI-sb for classifying SB sites.
Tolerance values for 35 additional taxa were derived using data from
six other regions of New Zealand combined with the Auckland data. The
interpretation of HB and SB versions of the MCI, SQMCI, and QMCI are
the same (i.e., "excellent": ≥120 or ≥6.00, "good": 100—119 or
5.00—5.99, "fair": 80—99 or 4.00—4.99, "poor": <80 or <4.00),
simplifying the use of these indices in State of the Environment
reporting. The MCI-sb performed better than the SQMCI-sb and is
recommended for assessing SB stream health. Standard methods now exist
for macroinvertebrate sampling, sample processing, quality control, and
reporting (biotic indices and quality classes) on the health of HB and
SB streams in New Zealand.
Keywords macroinvertebrates; organic pollution;
pollution tolerance; environmental variables; land use; habitat; water
quality; low gradient; submerged wood; macrophytes
New Zealand Journal of Marine and Freshwater Research, 2007, Vol. 41: 43—61
0028—8330/07/4101—0043 © The Royal Society of New Zealand 2007
M06051; Online publication date 12 February 2007. Received 17 August 2006, accepted 14 November 2006
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