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Determining the ecological health of estuaries in NW Tasmania: A case study assessing the status of the Duck, Montagu, Detention and Black River estuaries. NHT Final Report

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Hirst, AJ and Kilpatrick, R and Guest, MA and Probst, T and Crawford, CM (2007) Determining the ecological health of estuaries in NW Tasmania: A case study assessing the status of the Duck, Montagu, Detention and Black River estuaries. NHT Final Report. Project Report. Tasmanian Aquaculture and Fisheries Institute, Hobart.

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Abstract

Identifying suitable reference points is critical for effective monitoring of any natural system.
Here we utilize a comparative approach where putative impacts within two estuaries are
determined via comparison with two reference estuaries deemed to be relatively free of
human impacts. The two putatively impacted estuaries considered in this study were the Duck
and Montagu River estuaries situated on the NW coast of Tasmania. The river catchments of
these estuaries are typical of the region in that their catchments have become highly modified
through the clearance of native vegetation and subsequent replacement with intensive
agriculture, in particular dairy farming. Nutrient loadings (nitrogen and phosphorous) for
these catchments are amongst the highest in Tasmania. The catchments for the Black and
Detention estuaries, by comparison, are located for the most part in State Forest with limited
grazing in the lower catchment.
This study considered a range of water-column and sediment (benthos) based variables
commonly used to monitor estuaries. These included: salinity, dissolved oxygen, turbidity,
nutrient and chlorophyll a levels for the water-column; and sediment redox, organic carbon
content, chlorophyll a and macroinvertebrate community structure amongst the benthos. In
addition to comparing reference with impacted estuaries, comparisons were also made across
seasons, commensurate with seasonal changes in freshwater river input, and between regions
within estuaries (upper and lower reaches) - previously identified in Hirst et al. (2005). This
design enabled us to examine whether the detection of impacts (i.e. differences between
reference and impacted systems) was contingent on the time and location of sampling or
independent of these factors. Previous work had indicated that impacts may only be
manifested at certain times, and in certain regions, within these estuaries.

Item Type: Report (Project Report)
Publisher: Tasmanian Aquaculture and Fisheries Institute
Additional Information:

© Tasmanian Aquaculture and Fisheries Institute, University of Tasmania 2007
Copyright protects this publication. Except for purposes permitted by the Copyright Act, reproduction
by whatever means is prohibited without the prior written permission of the Tasmanian Aquaculture
and Fisheries Institute.

Date Deposited: 07 Apr 2008 16:08
Last Modified: 18 Nov 2014 03:37
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