Pumice is a volcanic rock notable for the characteristic of being able to float on water due to the air pockets trapped within its matrix. It is formed when magma is simultaneously rapidly depressurized, forming gas bubbles, and rapidly cooled, trapping these bubbles.
The pumice on these east coast beaches is believed to be the result of the 2012 eruption of a seamount (underwater volcano) in the vicinity of the Kermadec Islands, approximately half way between New Zealand and Tonga.
Riding on the pumice are a variety of organisms. These include stalk or goose-neck barnacles (Lepas species) which are familiar encrusting organisms on a range of floating objects and have a hard covering so they remain readily apparent when washed up and dried.
Other organisms that have been colonising the floating pumice, but aren’t readily apparent when it becomes beached and dried, include anemones.
With the help of Ian Shaw from Red Rock and Anna Scott from Southern Cross University the Australian Museum has received some samples of these anemones for the Marine Invertebrate Collection. The samples will be identified in the next few weeks when an expert on this group of invertebrates, Michela Mitchell from Museum Victoria, visits.
Anemones reproduce in a variety of ways, one of which includes a free swimming larval stage. However, it is unusual for the adults to move long distances. Therefore, identifying the specimens will help to provide a rare insight into long distance dispersal mechanisms and connectivity of adult populations.