Wetlands,Biodiversity and Salt

Changes in ecosystem structure and function August 2006

OverviewAs part of the Wetlands, Biodiversity and Salt project, a university project is examining changes in ecosystem structure and function in response to disturbance, using salinising wetlands as model systems.

Belinda Cant started this PhD research project in March 2004 and data collection will finish in February 2007. The project has been supervised by Dr Ralph MacNally, Dr John Beardall (School of Biological Sciences, Monash University) and Dr Sabine Schreiber (DSE).

AimThis work aims to investigate the impact of salinity on ecosystem structure and function.

Specifically, to

• better understand the way wetlands function; and

• examine the biodiversity within them. Both of these will be examined at a landscape scale.

Belinda works in the following areas of western Victoria:

• Corangamite• Glenelg-Hopkins• Wimmera.

She has examined small wetlands that differ in their salinity levels from fresh (<4000 EC) to hypersaline (>50 000 EC).

PhD student Belinda Cant Photo: Steve Morton

Measures of ecosystem function include productivity and decomposition. Ecosystem function is an important component of the health of ecosystems, along with biodiversity. Ecosystem function and biodiversity are often linked. Changes in ecosystem function are often a precursor to loss of species or changes in the composition of species in an ecosystem.

A Victorian Government

initiative

MethodsFor part of the work, Belinda measured the production and diversity of algae that live on top of lake sediments because they are present in fresh to hypersaline wetlands, and are the main primary producers in saline wetlands where there are no water plants.

Results• It is expected that diversity of algae will decrease with increases in salinity through space and time.

• On the other hand, algal biomass showed a humpbacked relationship with salinity as salinity varied across space with a peak at 100 000EC.

• In wetlands studied through time from wetting to drying, changes in salinity brought about by evaporation and rain directly affected algal biomass but only in the hypersaline wetlands.

• In medium saline wetlands, algal biomass increased through time responding to increases in light and temperature. Each freshwater wetland was unique in that algal biomass changes were inconsistent between sites and over time.

Management implications• Both fresh and naturally saline wetlands are at threat from increasing salinity in areas where soils and/or water tables are salty and where water tables move either laterally or vertically to intersect wetlands.

• Algae that live in wetlands are sometimes the major primary producers and form the basis of the food chain. While we don’t want to see algal blooms, wetlands need algae to function.

• Algae are one of the most salt-tolerant groups. Decreases in algal biomass seem to occur at 100 000 EC, which is twice the salinity of seawater.

• We may expect to see a loss of function in naturally saline wetlands when they are subject to secondary salinity that causes them to rise above 100 000 EC

Salinity history and changes in biota and ecosystems of the Western District Lakes AreaAnother part of the PhD will develop a method to investigate the salinity history of the area using data from several disciplines: ecology, paleoecology (ancient ecology), groundwater studies and social sciences (including interviews with landholders).

Published by the Victorian Government Department of Sustainability and Environment Melbourne, August 2006

© The State of Victoria Department of Sustainability and Environment 2006This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968.

Authorised by the Victorian Government, 8 Nicholson Street, East Melbourne.

ISBN 1 74152 616 7

For more information contact the DSE Customer Service Centre 136 186 or Belinda Cant on (03) 9905 5649 or belinda.cant@dse.vic.gov.au, Australian Centre for Biodiversity Analysis, Policy and Management; School of Biological Sciences; Building 18; Monash University; VIC 3800.

This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.

www.dse.vic.gov.au