The toxins affected multiple test targets …

Executive Summary – Investigations into the Toxicity of the George River. The summary is contained in the first part of the final report on our initial water (sampling).

The George River Water Panel has the full report and we await to see it loaded onto their website:

http://www.georgeriverwater.org.au/

Extract of Summary
Following an extensive oyster mortality event in 2004 a number of water samples were collected for chemical measurement and tested for manmade chemicals. No manmade chemicals were identified despite ongoing disease in the oysters.

In January 2005 chemical testing was abandoned in favour of toxicity testing. Two methods of collecting water samples were used; one method concentrates surface foam while the other collects a representative sample from the water column (called a grab sample). On January 17th 2005 two grab samples were collected from Pyengana and the North George River. Both were toxic to Sea Urchins and one was also toxic to oysters. During a storm event from the 2nd to 3rd of February 2005 two grab samples were taken, one of which was toxic from Moulting Bay. On the 14th of February 2005 five grab samples were taken and one was positive (Crystal Creek, although there was no clear documentation associated with this sample which was taken by DPIWE staff).

Thus, in the first two months of 2005 nine grab samples were taken four of which were toxic (although Crystal Creek method of collection is not known). All surface foam samples were toxic. Chemistry associated with these samples was not helpful in identifying a range of organic compounds, none of which were identified as manmade and the origins of these chemicals were unknown. The detection limits of these tests were also relatively high and could well have missed some manmade chemicals.

As indicated above the Government was aware of the January results leading to a combined sampling effort on the 14th of February 2005. Despite the oyster deaths and now finding toxic surface water as well as some toxic grab samples the Government decided it was natural and therefore not an issue and to the best of the authors knowledge stopped sampling for toxicity.

In the absence of any useful knowledge to allow management of this situation a Toxicity Identification and Evaluation (TIE) was commissioned (by the author, a local doctor and the oyster farmers). Due to funding constraints and scientific complexity, this section of the study took a considerable time being completed early 2008.

The TIE commenced in full in March 2005. The important findings are as follows.

1) The toxin(s) was present in surface foam during all dry weather samples.
2) The toxin(s) has a relatively short half life, days to weeks.
3) The toxin(s) is primarily attached to fine particulate matter but some remains dispersed or dissolved.
4) The toxin(s) are not chealatable metals.
5) The toxin(s) are not volatile.
6) The toxin(s) behaves like an organic chemical.
7) The toxin(s) is methanol soluble.
8) During March 2005 the toxin(S) was enhanced by the addition of PBO (suggesting a pyrethroid type chemical was present).
9) By mid April 2005 this PBO enhancement disappeared, toxicity did not.
10) By Mid April 2005 PBO suppressed toxicity suggesting an organophosphate type chemical was present.
11) Subsequent tests had no PBO effect but a methanol soluble toxin remained.
12) Chemistry was unable to confirm what the PBO effecting chemicals were.
13) Methanol fractionation indicated multiple toxins were present.
14) The toxins were not proteins.
15) The toxins were not of blue-green algal origin.
16) The toxins were unlikely to be of bacterial or fungal origins.
17) The toxins affected multiple test targets (Cladocerans, Oysters, Sea Urchins and three human cell lines) at similar concentrations.
18) The toxin(s) are not found downstream of natural forests.

At this point the leaves of the monoculture E.nitens plantations were tested. After a number of supporting tests (but not conclusive tests) an add back style of experiment was designed.
The rationale for this experiment is as follows:

*Picture: HERE

Download the Executive Summary to read the rest …
Tasmanian Investigation Summary.pdf