T H E PROBLEM O F OIL POLLUTION OF THE SEA
251
Field experiments with an " atmospheric residue " of crude oil
(approximating to a naturally weathered oil) showed reductions of 2040% in the population of the mobile winkles Littorina obtusata (L.) and
L. saxatilis (Olivi). The shells, encrusted with heavy oil, were carried
away by wave action on an exposed rocky shore. I n the laboratory,
this residue is non-toxic although a 6 h exposure to fresh crude oil,
followed by washing in clean water, caused mortalities of 34-44y0
in L. obfusata and L. littorea (Crapp, 1969a). Mironov (1967) found
rather lower mortalities from Russian crude oils tested on the gastropods Bittium reticulatum (da Costa), Rissoa euxinica Mil. and Gibbula
divaricafa L. ; kerosine was less toxic and a heavy fuel-oil had virtually
no effect. Limpets Patella vulgata L. survived for several months in
aquaria on rocks covered with weathered oil but died rapidly upon
contact with fresh crude in preliminary tests by Nelson-Smith (1968a).
They normally close down the shell to exclude noxious liquids, but
apparently fail to recognize the danger of the unfamiliar oil. Cockles
(Cardium edule L.) in aerated aquaria also quickly succumbed to
0.05% fresh Kuwait crude. Simpson (unpublished, 1961) found that
cockles exposed to toluene or a commercial aromatic solvent for up to
4 h and then washed in clean water suffered 25-30y0 mortalities in the
following week. The toxicity of naphthenic acids has not been reported
for marine molluscs, but with a pond snail (Physa heterostropha Say),
Cairns and Scheier (1962) obtained a 50% mortality in 96 h with
concentrations between 6.6 and 15.6 p.p.m. A comparable effect on
cockles requires over 500 p.p.m. phenol (Portmann, 1968).
Edible molluscs are frequently unsaleable because of oily taints.
Quahogs from some beds off Providence, R.I., have become quite
inedible (Hawkes, 1961) ; as little as 0.01 p.p.m. oil can give rise to a
marked taste in Crassostrea virginica and, after heavier doses, it may
persist for six months (Menzel, 1948). Mackin and Sparks (1962)
observed the similar persistence of taint for two months and the
Faulkner Report (Ministry of Transport, 1953) refers to Morecambe
Bay mussels (Mytilus edulis L.) which retained the oily taste for several
months after a spillage there.
5 . Other animals: plankton
Amongst the larger bottom-living animals, the echinoderms are
notoriously sensitive to any reduction in water quality, although as
the majority live slightly off shore they may escape the effects of floating
oil. Oily slurries have been used to form a barrier around oyster beds
to protect them from predatory molluscs and sea-stars. During the
" Tampico Maru " wreck, powerful surf filled the affected bay with an
251
Field experiments with an " atmospheric residue " of crude oil
(approximating to a naturally weathered oil) showed reductions of 2040% in the population of the mobile winkles Littorina obtusata (L.) and
L. saxatilis (Olivi). The shells, encrusted with heavy oil, were carried
away by wave action on an exposed rocky shore. I n the laboratory,
this residue is non-toxic although a 6 h exposure to fresh crude oil,
followed by washing in clean water, caused mortalities of 34-44y0
in L. obfusata and L. littorea (Crapp, 1969a). Mironov (1967) found
rather lower mortalities from Russian crude oils tested on the gastropods Bittium reticulatum (da Costa), Rissoa euxinica Mil. and Gibbula
divaricafa L. ; kerosine was less toxic and a heavy fuel-oil had virtually
no effect. Limpets Patella vulgata L. survived for several months in
aquaria on rocks covered with weathered oil but died rapidly upon
contact with fresh crude in preliminary tests by Nelson-Smith (1968a).
They normally close down the shell to exclude noxious liquids, but
apparently fail to recognize the danger of the unfamiliar oil. Cockles
(Cardium edule L.) in aerated aquaria also quickly succumbed to
0.05% fresh Kuwait crude. Simpson (unpublished, 1961) found that
cockles exposed to toluene or a commercial aromatic solvent for up to
4 h and then washed in clean water suffered 25-30y0 mortalities in the
following week. The toxicity of naphthenic acids has not been reported
for marine molluscs, but with a pond snail (Physa heterostropha Say),
Cairns and Scheier (1962) obtained a 50% mortality in 96 h with
concentrations between 6.6 and 15.6 p.p.m. A comparable effect on
cockles requires over 500 p.p.m. phenol (Portmann, 1968).
Edible molluscs are frequently unsaleable because of oily taints.
Quahogs from some beds off Providence, R.I., have become quite
inedible (Hawkes, 1961) ; as little as 0.01 p.p.m. oil can give rise to a
marked taste in Crassostrea virginica and, after heavier doses, it may
persist for six months (Menzel, 1948). Mackin and Sparks (1962)
observed the similar persistence of taint for two months and the
Faulkner Report (Ministry of Transport, 1953) refers to Morecambe
Bay mussels (Mytilus edulis L.) which retained the oily taste for several
months after a spillage there.
5 . Other animals: plankton
Amongst the larger bottom-living animals, the echinoderms are
notoriously sensitive to any reduction in water quality, although as
the majority live slightly off shore they may escape the effects of floating
oil. Oily slurries have been used to form a barrier around oyster beds
to protect them from predatory molluscs and sea-stars. During the
" Tampico Maru " wreck, powerful surf filled the affected bay with an