Uptake of heavy metals, organic trace contaminants and viruses by the Japanese oyster, Crassostrea gigas, grown in a waste recycling aquaculture system : final report
A study of 24 weeks duration was carried out in which oysters (Crassostrea
gigas) were grown in four regimes. These were: (i) on phytoplankton cultured
in a mixture of secondary treated sewage effluent and seawater for a
period of 12 weeks followed by a second 12 week period of feeding on phytoplankton
cultured in a "clean," inorganically enriched regime; (ii) as for
(i) except that the secondary effluent was sand filtered prior to use;
(iii) as for (ii) except that the effluent was charcoal filtered prior to
use; and (iv) using "clean," inorganically enriched phytoplankton food for
the 24 week duration. At intervals of two weeks, populations of oysters
were removed for assay for trace metals (Cd, Cr, Cu, Hg, Ni, Pb, Zn) and
organic contaminants (hydrocarbons, P . C.B.' s). No significant accumulation
or depuration of any metal or organic contaminant was evident in any of the
regimes. In terms of these contaminants all oysters are within acceptable
edible standards as set by F.D.A.
A series of experiments was carried out to examine the public health
implications of enterovirus survival in a mollusc culture system fertilized
with secondary treated sewage effluent. Using MS-2 bacteriophage and vaccine
strain poliovirus it would appear that depuration could be effected
in 20-25 days in C. gigas at l5°C. However this does NOT mean that such
a time span would be adequate for other enteroviruses. Further work is
required in this area.Supported by NOAA Office of Sea Grant, Department
of Commerce, Grant No. 04-07-158-44104
