250
A. NELYON-SMITH
fishery based on them closed after gathering only 9% of the normal
catch (Tegelberg, 1964). Commercial shell-fisheries suffered very little
during the “ Torrey Canyon ” wreck (Simpson, 1968a) largely because
the oil failed to reach the major oyster-layings. Shore molluscs suffered
very heavily from emulsifier spraying but survived where the oil was
left untreated (Nelson-Smith, 1968b).
Most toxicity studies have been on bivalves of commercial importance, particularly oysters (species of Ostrea and Crassostren). At
the beginning of adult life, these become permanently fixed to the
bottom and are thus subject to smothering by oil sinking en masse.
Almost all bivalves are filter-feeders; droplets of oil carried in the
inhalent current may collect within the mantle cavity and, if the oil
is emulsified or adsorbed onto silt particles, it may also cling to the
gills or pass into the gut (see Spooner, 1968a, b). Gowanloch (1835)
and Galtsoff et nl. (1935) investigated oyster beds near Louisiana
coastal oil wells and found no evidence that continuous slight oil
pollution caused mortality. They felt that it had a definite deleterious
effect, but this might have been due to the salinity of the “bleedwater ” from the wells or to a fungus disease which was not detected
until 1950 (see Mackin, 1962). Hawkes (1961) reported that quahogs
Mercenaria mercenaria L. seem to be “practically immune to oil
pollution . . . in Narragansett Bay (Rhode Island) where the bottom is
literally paved with oil ”. Oysters subjected to crude oil from a “ wild
well ” actually showed a lower mortality than those in clean adjacent
waters, perhaps because of its effect on their predators (Mackin and
Sparks, 1962). However, Gilet (1959) observed that the previously
abundant Chiton polii Marion was not t o be found on quaysides in
Marseilles which had become coated with oil around the waterline
(although there is evidence that chitons can graze away oil without
harm-see below, p. 268). Leenhardt ( I 925) showed that O . l - l . O ~ o
fuel-oil has an appreciable effect on oysters (Ostrea edulis L. and Crassostrea angulnta Lam.) and mussels (Mytilus galloprovincialis Lam.) ; 34% killed his specimens in less than a week. I n a variety of experiments (Galtsoff et al., 1935; Chipman and Galtsoff, 1949; Lunz, 1950)
the water soluble equivalent of 5-10y0 crude oil slowed down the pumping rate of oysters Crassostrea virginica Gmelin, probably by anaesthesia of the ciliated gill epithelium. Such oysters feed poorly and lose
condition. Where mobile molluscs such as shore gastropods become
anaesthetized, they are very vulnerable to predators-as was observed
during an unusually cold winter by Moyse and Nelson-Smith (1 964)but may be washed away to deeper water, reappearing on the shore
later as shown for some gastropods in Fig. 18.
A. NELYON-SMITH
fishery based on them closed after gathering only 9% of the normal
catch (Tegelberg, 1964). Commercial shell-fisheries suffered very little
during the “ Torrey Canyon ” wreck (Simpson, 1968a) largely because
the oil failed to reach the major oyster-layings. Shore molluscs suffered
very heavily from emulsifier spraying but survived where the oil was
left untreated (Nelson-Smith, 1968b).
Most toxicity studies have been on bivalves of commercial importance, particularly oysters (species of Ostrea and Crassostren). At
the beginning of adult life, these become permanently fixed to the
bottom and are thus subject to smothering by oil sinking en masse.
Almost all bivalves are filter-feeders; droplets of oil carried in the
inhalent current may collect within the mantle cavity and, if the oil
is emulsified or adsorbed onto silt particles, it may also cling to the
gills or pass into the gut (see Spooner, 1968a, b). Gowanloch (1835)
and Galtsoff et nl. (1935) investigated oyster beds near Louisiana
coastal oil wells and found no evidence that continuous slight oil
pollution caused mortality. They felt that it had a definite deleterious
effect, but this might have been due to the salinity of the “bleedwater ” from the wells or to a fungus disease which was not detected
until 1950 (see Mackin, 1962). Hawkes (1961) reported that quahogs
Mercenaria mercenaria L. seem to be “practically immune to oil
pollution . . . in Narragansett Bay (Rhode Island) where the bottom is
literally paved with oil ”. Oysters subjected to crude oil from a “ wild
well ” actually showed a lower mortality than those in clean adjacent
waters, perhaps because of its effect on their predators (Mackin and
Sparks, 1962). However, Gilet (1959) observed that the previously
abundant Chiton polii Marion was not t o be found on quaysides in
Marseilles which had become coated with oil around the waterline
(although there is evidence that chitons can graze away oil without
harm-see below, p. 268). Leenhardt ( I 925) showed that O . l - l . O ~ o
fuel-oil has an appreciable effect on oysters (Ostrea edulis L. and Crassostrea angulnta Lam.) and mussels (Mytilus galloprovincialis Lam.) ; 34% killed his specimens in less than a week. I n a variety of experiments (Galtsoff et al., 1935; Chipman and Galtsoff, 1949; Lunz, 1950)
the water soluble equivalent of 5-10y0 crude oil slowed down the pumping rate of oysters Crassostrea virginica Gmelin, probably by anaesthesia of the ciliated gill epithelium. Such oysters feed poorly and lose
condition. Where mobile molluscs such as shore gastropods become
anaesthetized, they are very vulnerable to predators-as was observed
during an unusually cold winter by Moyse and Nelson-Smith (1 964)but may be washed away to deeper water, reappearing on the shore
later as shown for some gastropods in Fig. 18.