30 September 2010 Streambed visitor surprises Waterwatch team

 

A miniature subterranean visitor has popped to the surface of Lincoln village’s Liffey Stream following the 4 September earthquake.

The sudden appearance in the Liffey of the underground-dwelling crustacean Phreatogammarus fragilis has surprised Lincoln University Waterwatch staff who have been monitoring and studying the stream in the village for over 10 years.

The creature, which is part of a family of micro-invertebrates inhabiting the gravels of groundwater systems, is translucent and about 5mm in length. It is known to live in aquifers and springs throughout central Canterbury.

It has been reported elsewhere in Central Canterbury, but Waterwatch Manager Kelvin Nicolle believes this is its first appearance in the Lincoln village stretch of the Liffey Stream.

“It seems likely that it may have been pushed to the surface of the streambed by the underground water surges that accompanied the earthquake,” says Mr Nicolle.

That’s a view supported by Lincoln University environmental scientist Dr Jonet Ward.

For positive identification the Liffey specimens were taken to NIWA where they have now been added to its reference collection for on-going taxonomic investigation.

NIWA’s Assistant Regional Manager, Dr Graham Fenwick, says that Phreatogammarus fragilis is often found in spring-fed streams, including the lower Selwyn River, and it’s presence in the Liffey is “not unexpected”. He personally doubts if the earthquake has had any effect on bringing the specimens to the surface, but says it is a question worth asking.

Mr Nicolle, who is a Senior Tutor in Environmental Water Quality at Lincoln University, says the specimens were collected from the Liffey just a few metres south of North Belt and downstream from an active spring. It is an area he has been sampling for over 10 years. He and Lincoln University postgraduate student Kate Collins were working with a Waterwatch group including students from Lincoln High School’s environmental group LEO (Lincoln Environmental Organisation).

Mr Nicolle says there is a healthy level of stream life in the Liffey, including plants for invertebrates to feed on.

“The water quality in the Liffey, although not ideal for drinking is fine for stream life.

“Creatures such as the Phreatogammarus fragilis and other subterranean micro-invertebrates, and a range of bacteria, play an important ‘housekeeping’ role in our waterways gobbling up organic material that sinks to the bottom of streams and finds its way into the underlying strata. Together with organisms carrying out similar processes above the stream beds,  they help clean our water.”

Mr Nicolle is pictured here examining the crustaceans with Lincoln University postgraduate student and Waterwatch assistant Kate Collins. (Photo courtesy Nelson Boustead, NIWA.)