Observations of change at previously surveyed saltmarsh sites

Mr Doug Fotheringham1, Ms Sharie Detmar2, Mr Jason Quinn2, Ms Alison Turner2, Ms Felicity Beswick2

1SA Herbarium DEW, Adelaide, AU, 2Coastal Management Branch DEW, Adelaide, AU

Over the last four years saltmarsh sites on Torrens Island, near Port Wakefield and at Port Pirie initially surveyed up to 30 years ago were revisited. On Torrens Island in 1990 a nine-hectare former sandpit was turned into a tidal saltmarsh and monitored.  A number of vegetation quadrats were also surveyed.  In 2015 the old photographs were compared and some of the quadrat sites were resurveyed. Due to land subsidence combined with sea level rise the island experiences a relative six-mm annual rise in sea level. Considerable change was observed which accords with the relative rise in sea level.  At Sandy Point near Pt Wakefield a 600 metre transect and two vegetation quadrats were originally surveyed in September 2000 and resurveyed in April 2018. Photographs along the transect were compared. A small landward shift in the saltmarsh communities was observed which accords with the expected effects of sea level rise.  At Pt Pirie a 3.2 km transect surveyed in November 1994 was resurveyed in November 2018. Five quadrats were resurveyed and photographs at 16 locations along the transect were compared. Considerable change was observed some of it through obvious human disturbance. Other changes appear to be from natural causes, whether these are from sea level change is unknown.  Pt Pirie  experiences land uplift and this is reflected in the long-term records of the tide gauge showing sea level falling. However, since 1997 the gauge has recorded a significant sea level rise  . More analysis is required.


Biography:

1976 :BA (Hons) Geography

1978 – 82: Woods and Forests Department

1982 – 2014: Coastal Scientific Officer with the Coastal Management Branch.

2015 – Current :Honorary Research Associate SA Herbarium

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