28
J. Haure et al.
filled with 1 kg mussels each and water temperature was regulated at 16
ı C. Several
treatments were set up at the start of the experiment, in which the mussels were
exposed to: (i) intact A. minutum or P. lima cells (toxic control); (ii) cell fragments
(lysate) recovered by centrifugation, after cell lysis by sonication in a culture volume
equivalent to that used in the toxic control; and (iii) dissolved toxins recovered in
the supernatant obtained after centrifugation made under the same conditions as in
(ii). Additionally, control mussels were exposed to S. costatum (a non-toxic algal
species).
Detoxification Trials
For trials on PSP-contaminated shellfish using non-toxic feed algae, either oysters or
mussels were placed in seawater tanks for a 4 day- acclimation period (16 ˙ 0.5
ı C)
and then put in experimental 150-L raceways or in individual 800-mL boxes,
depending on the different detoxification conditions being tested.
When using H 2 O 2 as a chemical treatment to improve phycotoxin breakdown,
60 kg of DSP-contaminated mussels were distributed between six baskets immersed
in 700-L tanks. Seawater used in the re-circulated flume was filtered and kept at
a constant temperature (16
ı C). Toxic mussels were either exposed to seawater
supplemented with a daily dose of hydrogen peroxide (trials) or kept in pure filtered
seawater (controls). Oxidant addition (to an accuracy of 1 ppm) was regulated by a
data-logger and computer system which provided a continuous recording of H 2 O 2
concentrations, with a platinum redox probe.
Safe Storage of Uncontaminated Shellfish
Oysters or mussels (180-kg) were stored in re-circulated systems at 16
ı C and
fed Skeletonema costatum for 35 days. The excretion of three dissolved nitrogen
compounds was monitored for each of the re-circulation systems, the first equipped
with a Pozzolana biofilter and the second without. The total ammonia level was
measured by the indo-phenol blue method (Solorzano 1969), nitrite was quantified
by the Greiss reaction (Bendschneider and Robinson 1952) and nitrate measured
using a Merkoquant Kit
® . Mortality rate, total body weight and soft tissues dry
weight were measured for both systems.
Chemical Analysis
PSP-toxin stability was assessed in natural or artificial seawater over 10–15 days
by liquid chromatography coupled with a fluorometer (LC-FLD). Toxic substances
were added to sea-water either as certified standards or as Alexandrium minutum cell
J. Haure et al.
filled with 1 kg mussels each and water temperature was regulated at 16
ı C. Several
treatments were set up at the start of the experiment, in which the mussels were
exposed to: (i) intact A. minutum or P. lima cells (toxic control); (ii) cell fragments
(lysate) recovered by centrifugation, after cell lysis by sonication in a culture volume
equivalent to that used in the toxic control; and (iii) dissolved toxins recovered in
the supernatant obtained after centrifugation made under the same conditions as in
(ii). Additionally, control mussels were exposed to S. costatum (a non-toxic algal
species).
Detoxification Trials
For trials on PSP-contaminated shellfish using non-toxic feed algae, either oysters or
mussels were placed in seawater tanks for a 4 day- acclimation period (16 ˙ 0.5
ı C)
and then put in experimental 150-L raceways or in individual 800-mL boxes,
depending on the different detoxification conditions being tested.
When using H 2 O 2 as a chemical treatment to improve phycotoxin breakdown,
60 kg of DSP-contaminated mussels were distributed between six baskets immersed
in 700-L tanks. Seawater used in the re-circulated flume was filtered and kept at
a constant temperature (16
ı C). Toxic mussels were either exposed to seawater
supplemented with a daily dose of hydrogen peroxide (trials) or kept in pure filtered
seawater (controls). Oxidant addition (to an accuracy of 1 ppm) was regulated by a
data-logger and computer system which provided a continuous recording of H 2 O 2
concentrations, with a platinum redox probe.
Safe Storage of Uncontaminated Shellfish
Oysters or mussels (180-kg) were stored in re-circulated systems at 16
ı C and
fed Skeletonema costatum for 35 days. The excretion of three dissolved nitrogen
compounds was monitored for each of the re-circulation systems, the first equipped
with a Pozzolana biofilter and the second without. The total ammonia level was
measured by the indo-phenol blue method (Solorzano 1969), nitrite was quantified
by the Greiss reaction (Bendschneider and Robinson 1952) and nitrate measured
using a Merkoquant Kit
® . Mortality rate, total body weight and soft tissues dry
weight were measured for both systems.
Chemical Analysis
PSP-toxin stability was assessed in natural or artificial seawater over 10–15 days
by liquid chromatography coupled with a fluorometer (LC-FLD). Toxic substances
were added to sea-water either as certified standards or as Alexandrium minutum cell