Bryozoan (cristatella mucedo) found living in colonies in the "Mid-Deûle" in the north of France - this fragile species seems to have appeared (or reappeared there) after import of clea water in the canal (over 2 million m3 / year)- . These animals lives in this case in a eutrophic water with sediments are polluted (formerly in constant contact with Upper-Deûle River, coming from the mining area (which were amongst the Métaleurop North Plant), on branches, wood piles, poles or walls ot the canal not or very rarely, and in this case may be accidentally) on the sediment of this ancient channel (that is no longer open to traffic, replaced by a full-size section last more northwest).