Nature Coast Marine Group column by Jenny Edwards

Lately some jelly-like creatures have been turning up in their millions along south coast beaches. They are salps, transparent, oval animals that are only about 5mm long. Each has a blue spot within its body that looks a bit like a blue eye although it is really its compact internal organs.

Salps found at Bermagui - Photo Jenny Edwards

Salps found at Bermagui - Photo Jenny Edwards

In spring 2012 people walking our southern beaches found larger salps washed ashore. The ones in the photo were particularly prolific at Bermagui. These two were taken to the estuary to be photographed and the adult handprint gives an indication of their size.

Fishermen said the sea was full of these "red-eyed blubbers" and that in places the water was coloured pink. These two phenomena are probably related as the salps were probably feeding on the pink coloured microscopic organisms.

Recent studies have suggested that the ocean's carbon cycle, and possibly climate change, could be affected by large changes in the distribution or abundance of salps and their relatives.

Salps are distantly related to the common Cunjevoi or sea squirts that cover the rocks near the low tide level in that they both have a spinal chord at some stage of their life cycle. Despite their primitive appearance salps are more closely related to animals with backbones than are most other invertebrates.

Salps are more or less cylindrical with an opening at one end to draw in water, a mucous net to trap food, tiny moving hairs called cilia that draw the net toward the opening to the gut, and another opening at the opposite end to expel the filtered water and wastes. Their see-through bodies have bands of muscles which are thicker but also transparent. The current created by the muscular contractions jet-propels the animals through the water. In the species photographed the gut is the compact "red-eye" at one end of the animal.

There are many species in Australian waters and they are very prolific near Antarctica. They can reproduce rapidly because of the two stages in their life cycle. Solitary animals can bud off chains of babies which remain attached to one another as they grow and are capable of sexual reproduction when they mature. Each animal in the chain is a female at first and is fertilised by older ones who have changed to males.

Nutrients upwelling off the east coast of Australia in spring and autumn result in blooms of microscopic plants - phytoplankton. Perhaps the pink sea was evidence of such a bloom. Salps feed so voraciously on phytoplankton that they eventually run out of food and most of the animals die. Their faecal pellets and the dead bodies that are not washed ashore drift to the bottom taking carbon with them. Recent studies have suggested that the ocean's carbon cycle, and possibly climate change, could be affected by large changes in the distribution or abundance of salps and their relatives.

The Nature Coast Marine Group welcomes new members. To find out more about the Group and to see other stories in this series, visit the website www.ncmg.org.au or search for Nature Coast Marine Group on Facebook and follow us there.