Geoscience Reference
In-Depth Information
Assessment of the contamination of the marine environment -
which is vast, chemically and thermically stable, and relatively
homogeneous in the oceanic areas - and of the consequences for the
associated ecosystems is, therefore, fundamentally different. In fact, it
is important to distinguish coastal environments from open oceanic
environments, situated beyond the continental plateau. The risks of
contamination in the coastal zone, to which estuaries and laguna can
be added, are fairly similar to those of continental environments, down
to a few specific details.
1.2.1. The coastal zone
This interface between the continent and oceans is home to specific
ecosystems where important transfers of matter, energy and genes
occur. The marshes, the seasonal nature of rivers' hydrology and the
pre-eminence of primary production confer on the coastal zone a
physico-chemical instability analogous to that of continental waters.
The biodiversity housed by coastal regions is adapted to the strong
variability in the characteristics of these transition environments, but
its resilience has been broken down by anthropic impacts, leading to
an increased vulnerability to pollution and global change, even more
critical in the case of islands and lagoons. The recipient of nutritive
salts eroded or washed from continents, the coastal and littoral zone,
which is not very deep, provides numerous services to ecosystems
(support and regulation especially) via primary production, the
recycling of major elements, the metabolization of contaminants or
their export into sediments and hydrological regulation. Costanza
et al . [COS 97] estimate that a third of the global benefits and services
to ecosystems are formed there. Because of this, but also due to the
access to waterways that they provide, as well as the attraction that
they exercise for our contemporaries, coastal areas concentrate 60% of
the world's population - which is becoming increasingly urban and
concentrated in megacities - at least 100 km from the coasts.
Coastal ecosystems, rich and vulnerable by nature, are therefore
subject not only to pressures provoked by global changes, including
climate change, but also to pressures due to this very strong
concentration of continental activities as well as maritime activities.
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