Members Handbook 20023 - ITOPF

and animals which are characteristic of
the habitat and are functioning normally
in terms of biodiversity and productivity.
Environmental Impacts
The exact nature and duration of any
impacts from an oil spill depend on a
number of factors. These include the
type and amount of oil and its behaviour
once spilled; the physical characteristics
of the affected area; weather conditions
and season; the type and effectiveness
of the clean-up response; the biological
and economic characteristics of the area
and their sensitivity to oil pollution.
Typical effects on marine organisms
range across a spectrum from toxicity
(especially for light oils and products) to
smothering (heavier oils and weathered
residues). The presence of toxic
components does not always cause
mortality, but may induce temporary
effects like narcosis and tainting of
tissues, which usually subside over
time. Some typical oil impacts are
described below.
Plankton
Their importance in primary
productivity of the oceans and as a
temporary home for the eggs and larvae
of fish, shellfish, sea bed and shoreline
organisms is well known, but is there
evidence of widespread harm to
these functions from spills which
subsequently translates into long-term
damage? Unfortunately, plankton is
extremely difficult to study reliably
because they are amongst the most
variable of marine communities in space
and in time. The presence of oil on open
water is also patchy and transient,
making it difficult to establish where and
when the plankton might have been
exposed to the oil. Laboratory studies
have demonstrated toxic and sub-lethal
effects on the plankton caused by oil,
and there is little doubt that there is
potential for widespread impact. Whilst
the possibility of long-term effects can
not be excluded, there is no indication
that oil-induced losses of eggs and larval
stages cause a significant decline in
adult populations.
Seabirds
Seabirds are amongst the most
vulnerable inhabitants of open waters
since they are easily harmed by floating
oil. Species that dive for their food or
which congregate on the sea surface are
particularly at risk. Although oil ingested
by birds during attempts to clean
themselves by preening may be lethal,
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