Marine Ecosystems under Toxic Pressure - Vulnerability of Coastal Ecosystems and Adaptation - page 6

gastropods (masculinization of the females by the effect called
imposex) [ABI 12]. Nanoparticles of titanium oxide, used in a lot of
sun protection products, are part of the emerging concerns.
Nevertheless, in their review on the subject, [KLA 09] do not report
any more observations in situ . Research is currently concentrated on
the evaluation in vitro of the potential effects of these nanoparticles on
coastal organisms [CAN 10]. Finally, the coastal zone permits active
exchanges between the column of water and the sediments, which
unfortunately often constitute a significant reservoir of persistent
contaminants. Much like continental lakes, the toxic threat associated
with them thus lasts decades, being reactivated following the
reshaping of the sediment or modifications of its “redox status”.
1.2.2. The open ocean
The risks from contamination of the open ocean by toxic
substances are different. There is less biodiversity there, which results
from the low habitat fragmentation of the environments, and from
their relative homogeneity. Nevertheless, marine ecosystems are of the
greatest importance for mankind: for their supply of protein biomass
(15% of the total supply) and for their value to local communities: the
cradle of life on Earth, still largely unexplored, is believed by some to
be outside the reach of anthropogenic pressures [GOU 12, p. 18].
They are home to wild species of great longevity, at the top of the
trophic chain.
One way of taking account of the immensity of the oceans and
their inertia consists of evaluating the residence time of elements in
their different compartments. This amount, homogeneous for a time, is
obtained by dividing the volume of a reservoir by the fluxes that cross
it, under the hypothesis of stationarity. The residence time of water in
the global ocean is in the order of 3,000 years [DE 09]. For the
Mediterranean, it is, for example, a hundred years. This means that an
easily biodegradable contaminant, carried from the continent, such as
glyphosate (in the order of a month in water, INERIS, 2010), will not
be found again in a significant concentration in the whole of the