Marsden Point Refinery: Lichen Monitoring

 

CLIENT: New Zealand Refining Company Ltd.

DATE: 1976 - ongoing

Studies

In March-April 1976 a photographic monitoring study commenced with the aims of providing ecological information on lichen populations within several kilometres of the Marsden Point Oil Refinery, providing a long-term record of lichen populations.   The lichens act as bioindicators of air quality and enable the evaluation of possible effects of sulphur dioxide emissions from the Refinery. 

 

This monitoring study is one of the longest running studies of its kind in New Zealand. The permanent quadrats have now been photographed seventeen times in March-April 1976, March-April 1979, April 1982, March 1987, April 1988, March 1990, July 1993, December 1994, December 1995, December 1997, December 1999, December 2001, December 2003, February 2005, December 2006, December 2008 and December 2010.

 

In 1990 a quantitative monitoring study of lichen populations commenced in parallel with the photographic study.  In 1993 the overall study was evaluated and it was decided to continue photographic monitoring only at those stations at which the quantitative study was being undertaken.

 

Lichens

Lichens are composed of two quite different organisms, a fungus and an alga.  They are essentially fungi, united only in having a common method of nutrition with the algae associated.  The resultant compound organisms behave as if they were single biological units and differ in so many ways from their free-living relatives that for convenience they are often regarded as a single natural group.

 

New Zealand is noteworthy for the richness of its lichen flora and has nearly one thousand species in more than 200 genera.

 

Lichens as a group are among the most highly sensitive plants to sulphur dioxide.  The effect of sulphur dioxide on photosynthesis by the algal cells is probably the main factor responsible for the sensitivity of lichens to that pollutant.   

 

Effects of sulphur dioxide on lichens vary widely.  In extreme conditions the total lichen flora is either eliminated or drastically reduced.  In intermediate conditions species diversity is reduced with the more tolerant species becoming dominant, while with sulphur dioxide levels about the lower threshold only a few species may be affected by sub lethal effects such as reduced growth rate and reduced fertility.