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Authors Robertson, HA; Funnell, EP
Author Full Name Robertson, Hugh A.; Funnell, Emily P.
Title Aquatic plant dynamics of Waituna Lagoon, New Zealand: trade-offs in managing opening events of a Ramsar site
Source WETLANDS ECOLOGY AND MANAGEMENT
Language English
Document Type Article
Author Keywords Ruppia; Macrophytes; Salinity; Water management
Keywords Plus ALTERNATIVE STABLE STATES; GENUS RUPPIA L; SOUTH-AUSTRALIA; LAKE ELLESMERE; SHALLOW LAKES; REGIME SHIFTS; SALINE LAKES; WATER; RESTORATION; MACROPHYTES
Abstract Coastal lagoons are at risk internationally due to impacts associated with human-induced land use change. The resilience of aquatic macrophytes in these systems is threatened by altered hydrological regimes, elevated nutrient loading, and increased dominance of nuisance species. We describe the aquatic plant dynamics of the Waituna Lagoon Ramsar Site, a 1,350 ha lagoon frequently opened to the sea for flood mitigation which is characterised by fluctuating water levels and salinity. The shallow lagoon supports a macrophyte community dominated by Ruppia megacarpa and R. polycarpa. Repeated survey of 48 sites across the lagoon during late summer in 2009, 2010 and 2011 were applied to describe aquatic plant composition and abundance. This period coincided with three opening events (winter 2008; winter 2009; spring 2010) when the lagoon switched from a predominantly fresh-brackish system to being influenced by tidal exchange and lower water levels. The lagoon experienced a period of 43 days open to the sea in 2008-2009, 67 days in 2009-2010 and 181 days in 2010-2011, during which macrophytes were subject to saline conditions in excess of 10 ppt. We observed a decline in the occurrence of Ruppia from 2009 (69 % sites) to 2011 (23 % sites). The shift in productivity was associated with the duration of the open phase and the period plants were subject to saline conditions > 20 ppt and low water levels. The resilience of the system is also at risk from increased algal-dominance due to the intensification of agricultural land use occurring in the Waituna Lagoon catchment. While lagoon opening events cause extreme changes in water depth and salinity that can limit macrophyte growth, they also provide a mechanism to reduce the effects of eutrophication. Understanding these trade-offs is pivotal in management decisions regarding the likely impact of opening events on the ecological character of coastal lagoons.
Author Address [Robertson, Hugh A.] Dept Conservat, Sci & Tech Grp, Christchurch 8443, New Zealand; [Funnell, Emily P.] Dept Conservat, Sci & Tech Grp, Invercargill 9480, New Zealand
Reprint Address Robertson, HA (corresponding author), Dept Conservat, Sci & Tech Grp, POB 11089, Christchurch 8443, New Zealand.
E-mail Address harobertson@doc.govt.nz
Funding Agency and Grant Number Department of Conservation (DOC) Arawai Kakariki Wetland Restoration Programme
Funding Text This project was funded by the Department of Conservation (DOC) Arawai Kakariki Wetland Restoration Programme. Wriggle Coastal Management (2009; 2010) and the National Institute of Water and Atmospheric Research (2011) implemented the field programme. Colleagues from DOC and Environment Southland provided field support and supplied data on water quality and lagoon hydrology. David Kelly assisted with analysis of light limitation. We appreciated comments from Philippe Gerbeaux, Eric Edwards, Eduardo Villouta, two anonymous reviewers and the associate editor on earlier versions of the manuscript.
Times Cited 9
Total Times Cited Count (WoS, BCI, and CSCD) 9
Publisher SPRINGER
Publisher City DORDRECHT
Publisher Address VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS
ISSN 0923-4861
29-Character Source Abbreviation WETL ECOL MANAG
ISO Source Abbreviation Wetl. Ecol. Manag.
Publication Date OCT
Year Published 2012
Volume 20
Issue 5
Beginning Page 433
Ending Page 445
Digital Object Identifier (DOI) 10.1007/s11273-012-9267-1
Page Count 13
Web of Science Category Environmental Sciences; Water Resources
Subject Category Environmental Sciences & Ecology; Water Resources
Document Delivery Number 018RZ
Unique Article Identifier WOS:000309681600006
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