Seagrass in the Pumicestone Passage

Seagrasses have long, grass-like leaves and are found in shallow, salty water. They are closely related to flowering plants on land but quite different to seaweeds (algae). Seagrasses have roots, stems, and leaves, and produce flowers and seeds. Seagrasses form dense meadows that trap sediment in shallow waters with sandy or muddy bottoms.

Seagrasses are found throughout the Pumicestone Passage. They provide important breeding grounds and nurseries for fish and invertebrates. Marine animals such as dugongs, green sea turtles and sea urchins depend on seagrass for food, and black swans regularly graze on seagrasses.

Seagrasses are protected under the Fisheries Act 1994, and council carries out regular seagrass surveys to map seagrass habitat and ensure its protection during sand dredging works in the Pumicestone Passage.

The area of seagrass distribution and the species composition depend on environmental factors, such as water quality and light availability. Two species of seagrass are currently found in the northern Pumicestone Passage, Zostera muelleri and Halophila ovalis. H. ovalis, commonly referred to as paddle weed or dugong grass, was mostly seen in subtidal areas. Z. muelleri was the dominant intertidal and shallow subtidal species observed during the surveys. Both species also occur in mixed meadows in shallow subtidal waters.

The Bribie Island breakthrough in early 2022 and large amounts of rainfall in 2021 and 2022 have a significantly reduced the extent of seagrass habitat in the northern Pumicestone Passage.

Find out more about the outcomes of our regular seagrass surveys.