A new species, Tisbe dahmsi sp. nov. (Crustacea, Copepoda: Harpacticoida: Tisbidae) is described from the Eiffel Tower edifice located in the Lucky Strike vent field (37 degrees N) (Mid-Atlantic Ridge MAR, 1698 m). The samples were collected in colonization experiments (SMAC arrays) that were deployed in 1997 during the MARVEL cruise and recovered in 1998 during the PICO cruise. Other specimens were collected during the MoMARETO cruise during which a physico-chemical characterization of copepod microhabitats was done. The new species belongs to the T. gracilis group based on similarities of the spine-like inner seta on the proximal endopodal segment of the male second swimming leg, which is terminally bifurcate. Re-examination of the closest relative and shallow-water species T. gracilis revealed a number of distinctions, including differences in shape and ornamentation of this terminally bifurcate seta. Tisbe dahmsi sp. nov. is found abundantly in the in situ colonization experiments (SMAC arrays) deployed on Bathymodiolus azoricus mussel assemblages at the Eiffel Tower edifice, together with the cyclopoid copepod Hepterina confusa Ivanenko & Defaye, 2004 (Cyclopoida: Cyclopinidae), the harpacticoid copepod Smacigastes micheli Ivanenko & Defaye, 2004 (Harpacticoida: Tegastidae) and the dirivultid copepod Aphotopontius atlanteus Humes, 1996 (Siphonostomatoida: Dirivultidae). Another colonization experiment, deployed near a black smoker, exhibits a different pattern with dominance of the harpacticoid families Ameiridae and Argestidae of the Ectinosomatidae family. These colonization experiments revealed that copepods of the genus Tisbe were substantially more abundant in the trays deployed on mussel assemblages than to those in the vicinity of black smokers. Nevertheless, no clear response regarding the effect of organic enrichment on copepod abundance was observed. The type of environment where the arrays were deployed appears to have a stronger influence on copepod abundances and composition than the treatment applied within each tray. Directly on the Eiffel Tower edifice, Tisbe copepods were found within different Bathymodiolus azoricus assemblages. These assemblages were alternatively dominated (in terms of copepods) by the Dirivultidae or the Tegastidae, the former being dominant in 67% of the samples. In terms of environmental conditions, Tisbe dahmsi was found in microhabitats characterized by low temperatures