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able to withstand 2 to 10 cm of oil with only slight, short-term,
floral composition changes. Apparently, most of the toxic fractions
had been lost from the Torrey Canyon oil, since it had been weathered
at sea for 2 to 18 days. Stebbings noted that oil appeared to form an
impervious layer on the substrate preventing gaseous interchange
between soil and air, causing reducing conditions in the mud, and
ultimately chlorotic symptoms in plants. Stands of Agropyron pungens
(Pers. ) R. and S. , Festuca rubra L. , Juncus maritimus Lam., and
Scirpus maritimus L. were extremely vigorous and seemed to derive some
nutritional benefit from the breakdown products of this Torrey Canyon
oil. Cowell and Baker (1969) noted that populations of annuals such as
Suaeda maritima (L. ) Dum. and Salicornia spp. near Pembroke, Southwest
Wales, were reduced initially but were recovering a year after oiling
from the Chryssi P. Goulandris. Halimione portulacoides (L.) Aell. was
the plant most badly damaged. In June 1968 the plant species with the
greatest coverage in the upper, middle, and lower marsh ( Festuca rubra ,
Puccinellia maritima , and Spartina townsendii , respectively) had
recovered completely (Cowell and Baker, 1969). Baker (1971a-i)
reported on several aspects of the effects of oil pollution on salt
marsh and concluded that single oil spillages do not cause long-term
damage to marsh vegetation (Baker, 1971a).
These studies indicate that marsh vegetation is resilient and
often can recover from single oil spills. Baker (1971e) suggests that
it is best to let an oiled marsh recover naturally. However,
persistent oil pollution has killed Spartina marsh at Southampton Water
(Ranwell, 1968). Such sites may develop extremely anaerobic conditions
in the mud so that higher plants can no longer grow on them. Cowell
(1969) states that repeated contamination is likely to have
increasingly serious effects if anaerobic conditions are created due to
bacterial use of oxygen in the biological oxidation of the oil. We
found no account of marsh recovery after removal of the upper layer of
marsh substrate and vegetation.
Study Sites
The lie Grande site is a relatively protected estuary with a mean
tide range of ca . 6 m, a spring tide range of ca. 8 m, and a mean tide
level of ca. 5 m. Our first visit to lie Grande was in December 1978.
Our NOAA liason representative, Douglas Wolfe, indicated that the marsh
west of the bridge at lie Grande was to be our primary study site (Fig.
1 ) . There were extensive stands of Juncus maritimus on both sides of
the estuary with lesser stands composed of a mixture of species
including Puccinellia maritima , Triglochin maritima L., Limonium
vulgare Mill., Spartina maritima (Curtis) Fern., and Halimione
portulacoides . There were vast areas with no vegetation cover, the
result of cleanup operations by the French military to rid the marsh
of Amoco Cadiz oil. In many areas only the aboveground marsh
vegetation and associated oil had been removed and in other areas the
entire marsh surface including the root mat had been removed to a depth
of over 30 cm. The intertidal creek banks were almost completely
lacking in vegetation cover. A limited number of substrate samples
from the disturbed sites were taken which subsequently indicated a
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