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van Bernem - Marine Sensitivity Aspects
The increase of degradation, however, remains doubtful because of possible changes of
microbial assemblages caused by the presence of dispersants (Kleindienst et al., 2015). Uptake
and metabolism of hydrocarbons by organisms is reported for many species. Unlike
bacteria, fungi and algae higher organisms tend not to utilise petroleum hydrocarbons as a
carbon source, but generally metabolize them if they possess mfo (mixed function oxidase) -
enzymes. The intermediate- and end-products of these metabolism processes very often
hold for a higher toxicity compared to the basic substances.
Last but not least, the effects of oil contamination may be strongly extended by the sedimentary
deposition of oil droplets and flocculae in anaerobiotic layers of sediments in areas of
low energy (sheltered bays, coves and creeks).
Investigations about these topics are numerous. But the results, aside from fundamental processes,
differ in terms of regions, times, methods and species of concern. Consequently
there is not enough systematically gained knowledge allowing a quantitative prognosis of
consequences in this regard for the German North Sea Coast.
Oil causes most damage in systems of low physical energy in which it can be trapped or
ponded for long periods of time. The most susceptible types of shore on this scale are mainly
associated with “shelter”, a physical concept involving protection from wind, wave and current.
Sheltered habitats are usually characterized by fine sediments and productive marine
communities, and many cases have been reported of considerable oil damage by direct
physico-chemical toxicity at the time of the spill or subsequently by long-term retention of the
oil in these areas. Conversely, least damage is likely to occur in systems of high physical
energy which turn over rapidly, and which may support impoverished communities of highly
adapted organisms resistant to physical stress, e.g. exposed rocky headlands. Lesser damage
to these systems may result partly from rapid removal of oil by physical means, partly
from the fact that communities may be of low productivity, and partly because the modes of
life of some species provide protection against physical (but not necessarily chemical) impacts
of oil (van Bernem & Lubbe, 1997; van Bernem, 2010).
Although such generalization inevitably has numerous exceptions, several authors have constructed
a simple, effective and widely applicable vulnerability scale for a range of shore
types based on geomorphological and biological characteristics which are globally applied.
They usually aim at a mitigation of intensity, duration and spatial extension of expected effects.
Ecology-related criteria are often achieved by including criteria concerning natural resource
protection.
The “Wadden Sea” - a sensitive environment
A contiguous region of tidal flats, barrier islands, alluvial terrestrial zones and salt marshes,
about 500 km long and up to 25 km wide, extends along the North Sea coast of Germany,
the Netherlands and Denmark. This „Wadden Sea“ is of enormous value as a cleansing site
for the coastal water, as a nursery for young fish, and as a feeding and nesting ground for
nearly all palaearctic species of wading birds and waterfowl. Predation is one of the most
important processes. It keeps densities of the large burrowing infauna (organisms living beyond
the sediment surface) below carrying capacity, thus positively influencing the amelioration
of the sediment.
The proximity of important shipping routes and ports is a permanent threat, especially to the
German part of the region, which became a national park in 1985/86. Large quantities of petroleum,
for example, which can be spread over wide areas by tides and winds, present not
only the danger of temporary damage but rather of permanent harm, since oil, bound to the
sediment, is released very slowly and can therefore repeatedly contaminate those parts of
the tidal flats that have become free of the oil.
