Scarratt and
Zitko () found that even though no lethal effects were apparent in
subtidal benthos in an area contaminated by the spill of Bunker C
fuel at Chedabucto Bay, many animals were still contaminated
twenty-six months after the spill, having petroleum hydrocarbons
with chemical "finger prints" like that of the Bunker fuel.
The effects
of oil pollution on subtidal seabed organisms have been seriously
neglected. Yet oil is often deposited in high concentrations on the
bottom, where it may persist and chronically repollute an
environment. Biodegradation and other weathering processes result
in a selective loss of n-alkanes so that the relative composition
of the oil persisting in sediments changes markedly as the total
quantity of oil is reduced (). The net effect is that the
hydrocarbons remaining are rich in aromatics and cycloalkanes which
may continue to be harmful.
Marine
organisms may accumulate petroleum hydrocarbons in their tissues
(). This may be especially true for benthic organisms, many of
which feed on suspended matter or bottom sediments which may
contain oil. The chronic effects of such contamination remain
unstudied, and it is unknown if petroleum hydrocarbons can be
transmitted to fishes feeding on oil-contaminated seabed
organisms.
WETLANDS
Tidal
wetlands are characteristic of many estuarine shores throughout the
world and include salt marshes dominated by grasses in temperate
climates, and mangrove swamps dominated by trees in the
tropics.
The great
value of wetlands in coastal ecosystems is generally accepted, if
not always well understood. They serve as habitat, feeding, or
nesting grounds for shore birds, fish, and other wildlife. Tidal
wetlands have been shown to be among the most productive
environments on earth, and it is this great productivity that
supports much of the life in estuaries through a food web based on
vascular plant debris (detritus). Wetlands also play a considerable
role as geological agents and are important to shoreline
stabilization.
Salt marshes
have generally proven to be resistant in the face of many types of
environmental onslaughts. In the case of oil pollution, they have
often suffered only minimal damage and have also alleviated the
pollution problem by trapping and holding oil. The frequent
proximity of marshes to sources of chronic hydrocarbon pollution
has given impetus to both post-accident and experimental studies of
the effects of oil. The first concerted studies took place in
Louisiana marshes and were sponsored by the oil industry in the
face of charges by fishermen of pollution from drilling (). These
studies involved experimental application of oil on marsh plants
with an assessment of changes in their biomass after treatment. The
experiments indicated that a moderate dosage of oil was not
excessively harmful, but that repeated applications proved lethal.
Oiling also apparently produced a "fertilizing" effect of
stimulated growth.