64
The Lust Resource
At least two contaminants do resist effort to remove them: the
marine toxin known as paralytic shell sh poison (PSP) and pesti—
cides. PSP is accumulated by the shell sh which feed on members
of the phytoplankton such as the red tide organism which contain
the toxin. Vast areas of clams off the north—west coast of the USA
cannot be exploited because they are known to be heavily con—
taminated with PSP—even transplanting such clams to unaffected
Î
areas has not been successful. The pesticides, on the other hand,
Ë
arrive in the water which runs off from agricultural land and can
È
occur in high concentrations where intensive seasonal spraying such
Î Ê
as occurs in fruit growing is carried out. As the following table
il
shows, shell sh can rapidly build up stores of these toxic chemicals.
‘i
Species
Amouut of DDT
in the
Exposure time
Amount of DDT
,
Environment
in days
in tissues
Eastern Oyster
Crassostrea oirginieu
10,000 ppm
7
151 ppm
Eastern Oyster
1,000 ppm
35
17 ppm
Pacic Oyster
1,000 ppm
7
20 ppm
Ï
Hard Glam Mereenariu
meræuurm
1,000 ppm
7
3—9 ppm
No account of marine farrning would be complete without some
mention of the larger seaweeds which fringe rocky shores all over
the world. In some coastal areas they increase agricultural yields
indirectly when spread as a rich organic manure over farmland—
weight for weight they contain twice as much potassium as farmyard
manure although they have only a third the phosphorus. However,
their cultivation as a direct source of food for man is much more
restricted. Sir Maurice Yonge has described the seaweeds eaten
in and around Britain: carrageen or Irish moss (C/rorzdrus erispus) in
Ireland and the Hebrides, dulse (Rlzodymeuu palmaz‘u) in Scotland,
and laver (Porphyra Luciuiur‘u or P. vulgaris) in England and Wales,
and also in Ireland where it is called sloke. One has to go to eastern
countries such as China, Japan, Malaya and some South Pacic
islands to nd peoples who value seaweed at all highly as food. By
way of contrast, the Atlantic provinces of Canada have ve species
which provide total harvests worth a million dollars a year, but of
these only one, dulse, is sold for direct human consumption and the
remainder are processed for use in the food and pharmaceutical
industries.
The Lust Resource
At least two contaminants do resist effort to remove them: the
marine toxin known as paralytic shell sh poison (PSP) and pesti—
cides. PSP is accumulated by the shell sh which feed on members
of the phytoplankton such as the red tide organism which contain
the toxin. Vast areas of clams off the north—west coast of the USA
cannot be exploited because they are known to be heavily con—
taminated with PSP—even transplanting such clams to unaffected
Î
areas has not been successful. The pesticides, on the other hand,
Ë
arrive in the water which runs off from agricultural land and can
È
occur in high concentrations where intensive seasonal spraying such
Î Ê
as occurs in fruit growing is carried out. As the following table
il
shows, shell sh can rapidly build up stores of these toxic chemicals.
‘i
Species
Amouut of DDT
in the
Exposure time
Amount of DDT
,
Environment
in days
in tissues
Eastern Oyster
Crassostrea oirginieu
10,000 ppm
7
151 ppm
Eastern Oyster
1,000 ppm
35
17 ppm
Pacic Oyster
1,000 ppm
7
20 ppm
Ï
Hard Glam Mereenariu
meræuurm
1,000 ppm
7
3—9 ppm
No account of marine farrning would be complete without some
mention of the larger seaweeds which fringe rocky shores all over
the world. In some coastal areas they increase agricultural yields
indirectly when spread as a rich organic manure over farmland—
weight for weight they contain twice as much potassium as farmyard
manure although they have only a third the phosphorus. However,
their cultivation as a direct source of food for man is much more
restricted. Sir Maurice Yonge has described the seaweeds eaten
in and around Britain: carrageen or Irish moss (C/rorzdrus erispus) in
Ireland and the Hebrides, dulse (Rlzodymeuu palmaz‘u) in Scotland,
and laver (Porphyra Luciuiur‘u or P. vulgaris) in England and Wales,
and also in Ireland where it is called sloke. One has to go to eastern
countries such as China, Japan, Malaya and some South Pacic
islands to nd peoples who value seaweed at all highly as food. By
way of contrast, the Atlantic provinces of Canada have ve species
which provide total harvests worth a million dollars a year, but of
these only one, dulse, is sold for direct human consumption and the
remainder are processed for use in the food and pharmaceutical
industries.