A woman who breached New Zealand's biosecurity laws by importing moss balls cried as she was sentenced today.

Jasmine Louise Maxwell, 20, a university student in Christchruch, had pleaded guilty to seven charges relating to breaches of the Biosecurity Act and the Hazardous Substances and New Organisms Act.

Maxwell imported moss balls and sold some online.

They are an aggressive algae used in the northern hemisphere to clean fish tanks but would have caused a disaster on the scale of didymo if they had got into New Zealand's waterways.

The moss balls are an absolutely prohibited import.

The Ministry of Primary Industries told the Christchurch District Court it was concerned that Maxwell wanted to work in the airline industry.

"She's a person who cannot be trusted to go through biosecurity on a very regular basis," prosecutor Grant Fletcher said.

He said the consequences of the moss balls being released "could have been utterly catastrophic and could still be catastrophic".

Biosecurity officials cannot tell if any of the moss balls she imported have got into the Avon River.

If only one filament has reached the river or the Avon-Heathcote Estuary it could cause an outbreak that would be difficult to control.

"It will be watched extremely carefully by the ministry," Fletcher said.

Judge Jane Farish ruled out a discharge without conviction and told Maxwell she was being over-emotive in saying the offending on her record would condemn her to life as a cleaner or shop assistant.

She should continue with her studies and get a good degree, the judge told her.

Maxwell would have to admit to employers that she had been silly when she was younger and had learnt a hard lesson.

Fletcher said Maxwell's offending had resulted from "immaturity, vast stupidity and youthful arrogance".

She had continued with her activities even after a warning from the ministry.

The court was told that Maxwell had a university qualification that included biosecurity. She is now working part-time and continuing to study.

Defence counsel Phillip Allan said Maxwell had been interested in the moss balls and had sold some for between $14 and $16 on Trade Me. She had not intended to make a lot of money out of the sales.

She had expressed her regret and had at times been overwhelmed by the prosecution. She had also been dealing with family and earthquake stress at the time.

"But for the earthquake, Miss Maxwell may be been thinking a little clearer and all this may not have happened," Allan said.

Maxwell began crying when the judge listed the maximum penalties, which include five years' jail and a fine of $100,000.

She told Maxwell: "The consequences of release within New Zealand would be severe. It would not be dissimilar to didymo. Control would be difficult to manage and expensive."

She assessed Maxwell as immature and recognised that she was highly remorseful. She accepted that her mind had not been "on the job" at the time.

The judge imposed a sentence of 250 hours of community work to reflect the seriousness of the offences, and said she hoped Community Probation could find an agency placement for her.

- © Fairfax NZ News