The Regional Estuaries Initiative supported the ongoing water quality, seagrass and macroalgae monitoring of the Leschenault Estuary since 2016 with monitoring continuing through Healthy Estuaries WA.

Below is the latest data about the condition of Leschenault Estuary.

Macroalgae in Leschenault Estuary

Macroalgae (or seaweeds) are a vital and natural part of many estuarine and marine ecosystems. They provide important habitat and food for many creatures, as well as perform essential ecological functions like oxygenating water and absorbing nutrients. However, an overabundance of macroalgae can become a problem, and often indicates too many nutrients in the water – so they can be indicators of water quality. Assessing macroalgae in estuaries forms part of our integrated understanding of ecosystem health.

As part of the Department of Water and Environmental Regulation’s (the department) seagrass monitoring, an annual snapshot survey occurs during the summer months in the Leschenault Estuary. Previous studies on the distribution and types of macroalgae have characterised seasonal patterns in abundance and distribution. These studies, combined with the department’s snapshots, can provide an idea of some (but not all) of the species that can be found in this estuary.

Macroalgae are generally grouped based on their appearance or pigment in their tissue. Some of the macroalgae found in the Leschenault Estuary include:

Red algae (Rhodophyta)

  • Chondria sp
  • Gracilaria sp
  • Laurencia sp

Brown algae (Ochrophyta)

  • Caulocystis sp
  • Dictyota sp
  • Hormophysa sp
  • Sargassum sp
  • Sirophysalis sp
  • Sphacelaria sp

     

    Green algae (Chlorophyta)

    • Acetabularia sp
    • Caulerpa sp
    • Chaetomorpha sp
    • Lamprothamnium sp (Charophyte)
    • Cladophora sp
    • Rhizoclonium sp
    • Ulva sp

    Macroalgae distribution in February 2020

    Image
    The area with macroalgae present in February 2020 was about 1,100 hectares – approximately 43 per cent of the estuary. Macroalgae was densest in the northern section, dominated by the green algae Chaetomorpha and Acetabularia, and the brown algae Caulocystis. Chaetomorpha and Caulocystis were also commonly found in the mid-section, as well as the green algae Caulerpa. Red algae, like Laurencia, favoured the southern section where there was greater marine influence, but were also found in lower numbers across the estuary.

    Historical observations

     A historical survey between 1984 and 1993 found that the brown algae Hormophysa was widely distributed in the northern section of the estuary, but was not observed in more recent department surveys. Red algae were also shown to reach maximum abundance in spring during this historical survey period, but seasonal patterns were not as clear for brown and green algae.

    Recent departmental snapshots of macroalgae have been opportunistic and coincide with the assessment of seagrass habitat. As such, identifying seasonal trends has not been possible in more recent years for macroalgae. Macroalgae snapshots will continue in the Leschenault Estuary as part of Healthy Estuaries WA and this page will be updated as new information becomes available.

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