Condition of Peel-Harvey
The Regional Estuaries Initiative supported the ongoing water quality, seagrass and macroalgae monitoring of the Peel-Harvey estuary since 2016 with monitoring continuing through Healthy Estuaries WA.
Below is the latest data about the condition of Peel-Harvey estuary:
- Seagrass data
- Macroalgae data
Key points
- The Peel Inlet has good water quality free from persistent symptoms of nutrient enrichment.
- The Harvey Estuary is poorly flushed and shows poor water quality with summer hypersalinity, high nutrient concentrations and, at times, elevated microalgal densities.
- The estuarine river reaches are in poor health. The Waangaamaap Bilya (Serpentine River) has very high nutrient concentrations that fuel microalgal activity year‑round with frequent blooms of potentially harmful microalgae.
- Oxygen in the bottom waters of the Bilya Maadjit (Murray River) is persistently low and occasional microalgal blooms and fish kills occur.
- Excessive nutrients and climate change impacts are key threats to the health of the Bindjareb Djilba (Peel-Harvey estuary) ecosystem. Reducing nutrient losses from the catchments is essential to build resilience and allow the estuary to adapt, especially considering climate change pressures are projected to increase.
Seagrass in Peel-Harvey
Seagrass meadows are an important part of estuarine ecosystems, providing habitat and food for birds, fish and crustaceans. They contribute to good water and sediment quality by consuming nutrients and oxygenating the water and are estimated to provide $12 million per year in ecosystem services to WA estuaries. Seagrass meadows also store carbon and release oxygen – making them a strong ally in the fight against climate change.
Seagrass condition and distribution throughout an estuary can provide important information about the overall health of the estuary and the quality of water entering it from streams, creeks, rivers and drains.
Several seagrass species are present within the Bindjareb Djilba (Peel–Harvey Estuary). Ruppia megacarpa (left image) is the most widespread species, typically occurring along the margins of both basins. Halophila ovalis (centre image) is common throughout the Peel Inlet, particularly in sheltered shallow waters. Heterozostera polychlamys (right image) and Zostera muelleri were combined in this study as they are morphologically1 similar and typically co-occur along the northern Harvey Estuary and the north-western shoreline of the Peel Inlet. In addition, anecdotal observations of Posidonia spp. and Amphibolis spp. have been recorded in recent years.
Ruppia megacarpa
Halophila ovalis
Heterozostera polychlamys
Seagrass over time in the Peel-Harvey
- Anecdotal reports suggest that seagrass was abundant in the early 1960s.
- Widespread loss of seagrass occurred in the 1970s-1980s due to smothering from
macroalgal blooms. - Seagrass all but disappeared in the southern Harvey Estuary after the mid-1980s.
- There was an increase in the abundance of seagrass, particularly within the Peel Inlet, after the Dawesville Cut was opened in 1994.
- In 2017 and 2018, seagrass was more abundant than macroalgae for the first time since the late 1970s.
- In 2021, seagrass covered 55 per cent of the estuary, though remained relatively absent in the southern Harvey Estuary, suggesting little to no recovery had occurred in this area.
2024-25 monitoring
The department monitored the extent and distribution of seagrass in February 2025, with a comprehensive survey of almost 500 observations. Seagrass covered an estimated 9,279 hectares, representing approximately 71 per cent of the total estuary area. Compared to 2021, total seagrass extent increased by 16 per cent, driven largely by expansion within the Harvey Estuary. Notably, the southern basin of the Harvey Estuary—previously supporting only sparse or minimal seagrass cover—now contains dense meadows, indicating a substantial increase since the 2021 survey. Overall seagrass density was low, with moderate to high-density meadows confined mainly to areas near the Dawesville Cut and along the eastern and southern margins of the Peel Inlet and
Harvey Estuary.
Ruppia continues to be the dominant seagrass species within the Bindjareb Djilba (Peel–Harvey Estuary), with recent expansion in the southernmost Harvey Estuary forming large single species meadows. Halophila was recorded extensively across the central Harvey Estuary, and throughout the northern Peel Inlet. Heterozostera/Zostera was observed in the northern Harvey Estuary and along the northwestern shoreline of the Peel Inlet, showing highest abundance near the Dawesville Cut and Point Grey, where salinity is more marine. The 2025 survey also confirmed continued presence of Posidonia australis in shallow areas adjacent to the Dawesville Cut, where salinity conditions are more stable.
Overall, the abundance of small organisms growing on seagrass leaves (epiphytes) was high, which can negatively affect seagrass health. However, in the southernmost Harvey Estuary, low to moderate epiphyte abundance suggests a reduced risk to ongoing seagrass establishment.
