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Quantitative Data: Impact of the introduced Sagittaria Upon native plant species of the wetland

Background: Melaleuca Swamp Forest is associated with poorly drained alluvial swamp flats, the community is characterised by a dense, closed canopy of small trees to 10m. Common canopy species include Melaleuca linariifolia (snow in summer) and Melaleuca styphelioides (Prickly-leaved Paperbark). Emergent trees such as Eucalyptus robusta (swamp mahogany) or Eucalyptus longifolia (woollybutt) to 20m are scattered throughout.

Purpose: To gather quantitative data on the impact of Sagittaria upon understorey plants within the Melaleuca (Paperbark) swamp forest.

Investigation Question 1 for Sagittaria How does the introduced weed Sagittaria influence abundance and distribution of native plant species?

Hypothesis 1 Sagittaria excludes native understorey plants from the Melaleuca (Paperbark) swamp forest of Porters Creek wetland.

Procedure: Belt transects are used to assess wetland vegetation.

1. Within the dry/fringing zone of the wetland, identify and mark a starting point for the transect.

2. Each belt transect will run across the flow of water (channel).

3. Where the length of the belt transect is <5 m, the entire length of the transect will be sampled as a

true belt, assessing the vegetation within a 1 m x 1 m quadrat which is then flipped over and over

to progressively create the 1 metre wide belt up to 5 m in length. When the length of a

transect is > 5 m the belt will become a series of five x 1 m² quadrats evenly spaced along the total length of the transect.

4. Each transect has 5 sampling points. This gives sufficient data to show patterns of distribution.

5. Within each 1m² quadrat identify each plant and then estimate and record its percentage cover.

6. Working in groups repeat steps A - E a minimum of four times. As each group is using the same method the data can be pooled to calculate average percentage cover of each plant along the transect. Improve the reliability by increasing the number of repetitions of each measurement and calculation of averages.

Use the images above to identify the plants in the quadrats. Estimate the percent cover of each of the species.

Click on the image below and use the arrows to see photos of quadrats from 0m - 10m along the transect

Record the water quality results from the 12th October 2021. Use the ANZEC Guidlines to determine if the water quality results are good or bad.

4. Quantitative Data: Impact of the introduced Eastern Gambusia upon native fishes

Background: Primarily carnivores - Eastern Gambusia feed on a range of small freshwater invertebrates, windblown terrestrial insects, and the eggs, larvae and juveniles of native fishes and frogs. Eastern Gambusia had previously been referred to as Mosquito Fish as they also eat mosquito larvae.

Purpose: To gather quantitative data on the impact of Eastern Gambusia upon native fishes.

Investigation 2 Investigation Question 2: What is the ratio of native fish to the introduced Gambusia?

Hypothesis 2 Gambusia excludes native fish species from the Porters Creek wetland.

Procedure Dip netting can be used to sample small fish populations.

Gambusia were captured with long handled dip nets 40cm X 40cm and 1 mm mesh size. This technique has a low impact on the aquatic environment, and is a suitable method for small-sized target species.

• Identify an edge where there is both safe access and sufficient water to use the dip net.

• Make one long pass of the net through the water and check for fish and other species.

• Separate fish from macroinvertebrates by placing the fish into a container for counting.

• Count the number of Gambusia captured.

• Repeat steps 1-5 three Repeat steps 1-6 in another two locations along the wetland water’s edge.