Meet the tiny creatures that make Cockburn Sound their home

Researchers from Edith Cowan University, Murdoch University and the Western Australian Museum (WAM) have found thousands of tiny marine animals known as benthic invertebrates living on top of and among the sediments in and around Cockburn Sound and Owen Anchorage.

The research team used a Van Veen Grab Sampler (see photo) that is lowered from a boat to scoop sediment from the seafloor.

Sediments from 30 sites across two seasons were sieved to remove fine mud, leaving behind coarse sediment and animal inhabitants. Hundreds of hours have been spent carefully sampling the sieved material, tablespoon-by-tablespoon, to locate and separate the often-fragile animals from the sediment. Taxonomists at WAM are working continuously to identify the species characterising the hidden diversity of this urban seafloor habitat.

Invertebrates are important because they play a significant role in healthy ecosystems as food for commercially important species, as burrowers of sediments and by utilising multiple life strategies such as parasitism on larger animals.

Sorting and species identification continue, but currently over 17,000 individuals from eight major invertebrate groups have been found. The individuals comprise a whopping 200+ unique species! Many are adult worms, snails, crustaceans, urchins and bivalves (see photos) ranging from 1-5 mm in size.

A selection of benthic invertebrates from Cockburn Sound. From top to bottom, left to right; a seed shrimp Ostracoda sp., a side swimmer Amphipoda sp., the date shell Solemya sp., a copepod, the sea urchin Temnopleurus michaelseni, the parasitic snail Eulimidae sp., a tellin clam Tellinidae sp., another side swimmer amphipod Ampelisca sp., and the Venus clam Veneridae sp. (Photographs: Henry Carrick)

This research is being conducted under the WAMSI Westport Marine Science Program. It is the first benthic survey targeting invertebrates to be carried out at this scale in the Cockburn Sound area, and the sheer quantity and diversity of invertebrates has been an interesting and exciting discovery. The data produced from this work will tie into similar projects focused on the abundance, diversity, distribution and diets of larger animals in Cockburn Sound and the ecosystem that they all form a part of.

Author: Henry Carrick, Sorcha Cronin-O’Reilly, Leah Beltran, Ana Hara, Oliver Gomez, Peter Middelfart, Lisa Kirkendale, Andrew Hosie, Glenn Hyndes & Zoe Richards

Feature Image: Henry Carrick (Edith Cowan University) about to lower the Van Veen Grab Sampler to the seafloor where it will automatically close, capturing a fixed quantity of sediment (Photograph: Glenn Hyndes)