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The bio-concentration is the direct in crease in concentration of a pollutant when it passes from water in a watery organization. The
has bio-accumulation is the sum of absorptions of a pollutant per direct and food way by
watery species. This phenomen on of bio-accumulation is well-known thanks to certain
species able to accumulate amounts of natural substances several thousands of times beyond
the concentration which one meets in the ground. Thus, the algae of the wrack types or
Laminaria are able to accumulate bromine and iodine present in the water of the seas what
is made profitable in the industrial extraction of these products Plutor ejected by the
man in the oceans coming from the treat ment plants of the radioactive waste can be
concentrated up to 3000 times by the phytoplankton and 1200 times by the benthic algae.
This phenomen on has as a consequence a transfer and a biological increase in pollution
inside the contaminated biocénoses. Each trophic chain will be the site of a process of
increase in concentration in the persistent pollutants in the biomass as one goes up in
the various levels of the ecological pyramid.
In the natural middle, one can consider, except extreme cases, that the
organizations are in the presence of concentration of insufficient pollutant to kill them.
But even if short-term effects are thus not always visible in the long run, on the other
hand, one ends up feeling effects on the respiratory and nutritional behaviors.
The presence of phosphate, of nitrogen ammoniacal and organic and of
nitrate, support the nutrition of the algae. According to the concentration of these
various products, it may be that the diversity and the productivity of the algae are
affected. Thus the knowledge of the
rate of absorption of organic nitrogen by algae of mediums polluted such as Anteromorpha
and Ulva, can give a base of explanation of the pullulation of species to depend on
others. Indeed, these algae showed a great facility of assimilation of amino acids present
in waste water and rich in organic matter. On the contrary, the soft red algas and the
brown algas have a weak capacity of accumulation of these amino acids. What could explain,
partly, disappearance in the polluted zones of the Mediterranean of the brown algas of the
kind will cystoseira, replaced either by the calcified red alga Corollina,or by of
Protofloridées, or by of Ulva or Entéromorpha.
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Copyright - manon.org - 02/01/2000 -
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