- Last updated:
- 08 Mar 2019
Our local seagrass communities
Seagrass beds are often the most productive communities in nature, forming meadows in estuaries and shallow coastal waters with sandy or muddy bottoms. Seagrasses, such as those found in Pumicestone Passage, are important breeding and feeding grounds for large numbers of fish and invertebrate species, and provide a critical food source for dugongs and turtles. These areas provide important functions in our waterways including carbon and nutrient sinks, water and sediment filters.
The Pumicestone Passage is recognised as having national significance and as such council was requested by the state and federal government to map seagrass communities since 2011. As surveyed in 2015, the Pumicestone Passage contained 11.5 hectares of seagrass habitat with a variety of seagrass meadows including:
- Zostera muelleri ssp capricorni (hereafter referred to as Zostera muelleri)
- Halophila spp (including H. ovalis, H. spinulosa and H. decipiens)
- Halodule uninervis has also been recently identified within the passage.
The most widespread seagrass in the Pumicestone Passage
Seagrass communities in the Pumicestone Passage generally appear to have changed little over the last two decades (McKenzie and Yoshida 2013). Mapping surveys have been carried out in 2011, 2014, 2015 and 2016. The seagrass meadows are generally dominated by Z. muelleri and H. ovalis, with Z. muelleri identified as the most widespread. This is consistent with descriptions of seagrass meadows in the Moreton Bay region of South East Queensland.
Zostera muelleri, commonly known as Eel-grass, is a dominant seagrass of the intertidal zone, often exposed at low tide, and spread by rhizomes. It grows well in soft mud or sand, where many animals depend on it for food. It also provides hiding places for young animals trying to escape from predators.
Seagrass may look like some seaweeds, but it’s actually quite different. In reproduction, it bears flowers, fruits, and seeds just like many terrestrial species that live on land. Their leaves support an array of seaweeds and tiny filter-feeding animals, and they help to keep the water clear. Animals such as the pictured Idiosepius paradoxus (Northern Pygmy squid), identified in the Pumicestone Passage, shelter in the seagrass beds.
Idiosepius paradoxus Pygmy squid is associated with seagrass (Zostera) beds (Kasugai and Ikeda 2003). Pygmy squid grow to about 16mm. On top of their tiny size, Pygmy squid have glue gland on their dorsal surface, releasing a sticky glue from their skin that allows them to attach themselves to seaweed, seagrass, rocks, and other objects within reach. This adaptation is particularly helpful in allowing the Pygmy squid to blend in with its surroundings. Females spawn repeatedly with a single individual laying as many as 42 batches over a 70 day period (Kasugai 2006). An egg mass may contain up to 178 eggs (Kasugai and Ikeda 2003). Pygmy squid feed on crustaceans such as crabs and shrimp.
I hope you enjoyed learning more about our beautiful Pumicestone Passage. Next year I look forward to sharing information on other seagrass species.
Written by Michele Jackson, SCC Environmental Operations Senior Project Officer