PDF Hirst_and_Kilpa...pdf | Request a copy Full text restricted Available under University of Tasmania Standard License.

Abstract

As human impacts in estuaries are often pervasive (estuary-wide) and/or pre-existing, the identification of
suitable reference points, from which to assess the extent of impacts, is problematic. One solution is to compare potentially
degraded estuaries with estuaries deemed to be largely unmodified by human activities. However, there is a perception
that individual estuaries are too spatially and temporally dynamic to allow valid comparisons to be made using such
an approach. We tested this idea for a commonly used indicator, benthic macroinvertebrates, using a factorial design
incorporating both temporal and spatial scales between and within three adjacent meso-tidal river estuaries in northern
Tasmania. Variation in macroinvertebrate assemblage structure was analysed using permutational multivariate analysis
of variance. Most variance occurred within estuaries (68–82% variance) relative to spatial differences between estuaries
(24–14%) corresponding with a strong upstream estuarine gradient and small-scale spatial patchiness. Seasonal variation
accounted for 9–4% of total variance indicating that temporal differences were relatively insignificant when contrasted
against spatial variability within and between estuaries. We suggest that with sufficient spatial replication at the within
estuary-scale, entire estuaries may act as whole reference systems, allowing studies to examine potential impacts within
estuaries with spatially diffuse, pre-existing human impacts.

Item Type:	Article
Authors/Creators:	Hirst, AJ and Kilpatrick, R
Keywords:	environmental gradients, multivariate variance components, salinity, sediment, Tasmania.
Journal or Publication Title:	Marine and Freshwater Research
Publisher:	CSIRO
ISSN:	1323-1650
DOI / ID Number:	https://doi.org/10.1071/MF06219
Item Statistics:	View statistics for this item

Actions (login required)

Item Control Page