Victorian Multi-regional Seagrass Assessment
Seagrass Habitats
Seagrass meadows are an important marine habitat in Victorian waters. Seagrasses are flowering plants that form highly productive ecosystems and provide food and shelter for a rich assemblage of marine life. Seagrass beds provide critical habitat for adult fish as well as playing an important role as nursery areas for many juvenile fish species. Seagrasses also play an important role in trapping and stabilising fine sediments.
Seagrass Species and Distribution
The main seagrass species found in Victoria are Heterozostera tasmanica, Heterozostera nigricaulis, Zostera muelleri, Halophila australis, Posidonia australis and Amphibolis antarctica. The predominant seagrasses in Victoria’s sheltered bays and inlets are species of Zosteraceae, commonly known as eelgrass. Zostera muelleri typically inhabits the intertidal flats. The subtidal species of Zosteraceae in Port Phillip Bay and Western Port was previously classified as H. tasmanica, but following the recommendations of a recent study (Kuo. J. (2005) A revision of the genus Heterozostera (Zosteraceae), Aquatic Botany 81: 97–140) has been reclassified as the newly described H. nigricaulis.
Corner Inlet is the only Victorian bay where the broad-leaved Posidonia australis is abundant, inhabiting the shallow subtidal zone.
 Heterozostera nigricaulis (Port Phillip Bay) Photo: Guy Werner |  Zostera muelleri (Port Phillip Bay) Photo: Guy Werner |  Posidonia australis (Corner Inlet) Photo: Jeremy Hindell |
Project Background
Seagrass health is affected by a wide range of natural and human disturbances that occur at a range of spatial and temporal scales. Large fluctuations in seagrass abundance have been observed across Victoria’s bays in the past, but a lack of quantitative baseline data has been a barrier to identifying causes of die-back episodes.
To assess the status of seagrass across Victoria’s major embayments, a three year monitoring program commenced in December 2004. The project is being undertaken by Primary Industries Research Victoria (PIRVic) – Marine and Freshwater Systems with a grant from the Natural Heritage Trust.
Study Sites
The project is studying seagrasses in Port Phillip Bay, Western Port and Corner Inlet, with three monitoring sites established in each bay. An additional site at Blairgowrie in Port Phillip Bay is being monitored by aerial photography interpretation only.
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Seagrass Monitoring Techniques A multi-faceted approach has been adopted for the seagrass monitoring that addresses seagrass health at different spatial scales. Intertidal and shallow subtidal seagrasses are sampled at fixed points within each of the monitoring sites twice a year (start and end of summer). Measurements of seagrass biomass are made in the field and samples are collected for analysis in the laboratory. The seagrass samples are analysed for leaf length, shoot density, epiphytic algae and grazing animals. The role of seagrass seeds in natural regeneration of beds is also being investigated by measuring seed densities in the sediment. |  Seagrass sampling in Western Port |
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Aerial Imagery Broad-scale changes in seagrass are being assessed through interpretation of aerial photography. Aerial photography is flown each year under calm sea conditions and at low-tide to allow seagrass area and distribution to be mapped at the monitoring sites. All mapping and aerial photography interpretation is undertaken with a Geographic Information System (GIS). |
Light Seagrasses are just like other plants and need sunlight for photosynthesis. Water clarity is an important factor in determining the availability of light to seagrasses. Available light at each monitoring site is being measured through special underwater light meters. These light meters are fitted with a self-cleaning wiper system developed by PIRVic to keep the light sensor free of algae and other marine foulants. |  Underwater light meter |
Acknowledgements
This project is funded through a Natural Heritage Trust Statewide project grant. The project was developed with the support of the Port Phillip and Western Port CMA, West Gippsland CMA, Department of Sustainability and Environment, Parks Victoria and the Environment Protection Authority.
Contacts
For further information about this project please contact the following:
David Ball: Section Leader, Fish & Habitat Ecology
or
Greg Parry: Senior Marine Scientist
Department of Primary Industries - Queenscliff Centre
P.O. Box 114
Queenscliff,
Victoria, 3225
Phone: (03) 5258 0111
E-mail: David.Ball@dpi.vic.gov.au
Greg.Parry@dpi.vic.gov.au
Related Links
National Action Plan for Salinity and Water Quality (NAP) and the Natural Heritage Trust (NHT) in Victoria (external link)
Natural Heritage Trust (external link)
National Action Plan for Salinity and Water Quality (external link)
Seagrass mapping in Victoria. (external link)
National Action Plan for Salinity and Water Quality (NAP) and the Natural Heritage Trust (NHT) in Victoria (external link)
Port Phillip and Western Port CMA (external link)
West Gippsland CMA (external link)
© The State of Victoria, 1996 - 2008.
This document was last reviewed on 11/09/2008