T H E PROBLEM OF OIL POLLUTION OF T H E SEA
259
tailed duck Clangula hyemalis of NW Europe, but as early as 1960 the
number of migrants there was only one-tenth that recorded in 193740 (Bergman, 1961). Eider Somateria mollissima (L.) and shelduck
Tadorna tadorna (L.) also congregate over-winter or for moulting in
areas subject to pollution incidents (see Bourne, 1968a; Clark, 1968).
The auks are, however, probably the most seriously affected. They
are long-lived with few natural predators, and have an extremely
low reproductive rate. Guillemots, Uria aalge (Pont.), do not breed
until they are three years old and then produce one brood per year,
usually of only one egg. According to Tuck (1960) and Southern et al.
(1965), in several species of this genus only 20% of the eggs laid produce
chicks which safely reach the sea and many of these drown or are taken
by gulls in their first days on the water. Clark (1968) estimates that if
an oil spill halved a guillemot colony, it would take more than half a
century for it to recover. Most auk colonies on each side of the North
Atlantic are situated in regions particularly subject to oil pollution.
Puffins, Fratercula arctica, which numbered 100 000 on Annet (Isles of
Scilly) in 1907 have been reduced to 100 in 1967 (Parslow, 1967a, b)
and similar declines have been recorded at other colonies. The process
is an accelerating one, since smaller colonies have proportionally less
reproductive success and suffer greater losses of eggs and young (Clark,
1968).
It is a commonplace that areas subjected t o chronic pollution,
whether industrial, domestic or natural (e.g. of sea water by fresh
water and silt from a river), usually support a less diverse population
than similar unpolluted sites, although the numbers of the few resistant
species may be very large. I n this respect, oil is little different from
other pollutants (see, for example, Gilet, 1959; Reish, 1964). A catastrophic pollution incident results in a similar selection of resistant
species, but the system has no time in which to reach a new balance.
The " Tampico Maru" wreck (North et al., 1964) provides a good
example of the ecological effects of a serious oil spill. One of the main
factors restricting the spread of the giant kelp Macrocystis pyrifera is
the grazing of young plants by species of sea-urchins Strongylocentrotus
and of abalones Haliotis. Although the kelp itself suffered immediate
damage from the diesel oil spilt from the wreck and emulsified
by wave-action, juvenile plants began to appear within 2-3 months.
North and his colleagues suggested that their settlement was assisted
by severe reductions in the population of filter-feeding mussels and
scallops, which did not therefore take their customary toll of the
swimming kelp spores ; but the major biological factor which made
possible the great development of the kelp canopy over the next five
259
tailed duck Clangula hyemalis of NW Europe, but as early as 1960 the
number of migrants there was only one-tenth that recorded in 193740 (Bergman, 1961). Eider Somateria mollissima (L.) and shelduck
Tadorna tadorna (L.) also congregate over-winter or for moulting in
areas subject to pollution incidents (see Bourne, 1968a; Clark, 1968).
The auks are, however, probably the most seriously affected. They
are long-lived with few natural predators, and have an extremely
low reproductive rate. Guillemots, Uria aalge (Pont.), do not breed
until they are three years old and then produce one brood per year,
usually of only one egg. According to Tuck (1960) and Southern et al.
(1965), in several species of this genus only 20% of the eggs laid produce
chicks which safely reach the sea and many of these drown or are taken
by gulls in their first days on the water. Clark (1968) estimates that if
an oil spill halved a guillemot colony, it would take more than half a
century for it to recover. Most auk colonies on each side of the North
Atlantic are situated in regions particularly subject to oil pollution.
Puffins, Fratercula arctica, which numbered 100 000 on Annet (Isles of
Scilly) in 1907 have been reduced to 100 in 1967 (Parslow, 1967a, b)
and similar declines have been recorded at other colonies. The process
is an accelerating one, since smaller colonies have proportionally less
reproductive success and suffer greater losses of eggs and young (Clark,
1968).
It is a commonplace that areas subjected t o chronic pollution,
whether industrial, domestic or natural (e.g. of sea water by fresh
water and silt from a river), usually support a less diverse population
than similar unpolluted sites, although the numbers of the few resistant
species may be very large. I n this respect, oil is little different from
other pollutants (see, for example, Gilet, 1959; Reish, 1964). A catastrophic pollution incident results in a similar selection of resistant
species, but the system has no time in which to reach a new balance.
The " Tampico Maru" wreck (North et al., 1964) provides a good
example of the ecological effects of a serious oil spill. One of the main
factors restricting the spread of the giant kelp Macrocystis pyrifera is
the grazing of young plants by species of sea-urchins Strongylocentrotus
and of abalones Haliotis. Although the kelp itself suffered immediate
damage from the diesel oil spilt from the wreck and emulsified
by wave-action, juvenile plants began to appear within 2-3 months.
North and his colleagues suggested that their settlement was assisted
by severe reductions in the population of filter-feeding mussels and
scallops, which did not therefore take their customary toll of the
swimming kelp spores ; but the major biological factor which made
possible the great development of the kelp canopy over the next five