[en] A suite of natural radionuclides including ²¹⁰Pb-²¹⁰Po was analysed in atmospheric deposition, seawater, suspended particulates and abyssal fauna from the NE Atlantic Ocean. Measurements of dry and wet atmospheric fallout show that most of the ²¹⁰Pb and ²¹⁰Po in surface seawater originates from atmospheric deposition. In surface seawater near Madeira, ²¹⁰Pb and ²¹⁰Po concentrations average 2.1±0.7 and 1.5±0.7 mBq 1^-1, respectively. ²¹⁰Pb was in excess over ²²⁶Ra in the upper mixed layer but below 500 m the ²¹⁰Pb/²²⁶Ra ratio was less than 1 due to preferential scavenging of ²¹⁰Pb by particles. Seawater profiles of ²¹⁰Po and ²¹⁰Pb indicated a well-defined maximum of ²¹⁰Po between 250-500 m. Based on activity levels measured in water and suspended particulates in the Iberian and Porcupine abyssal basins, mean residence times of 5 y and 1 y were computed for soluble ²¹⁰Pb and ²¹⁰Po, respectively. A much shorter residence time of 0.6 y was computed for the particles that scavenge both radionuclides. Analysis of a variety of abyssal organisms demonstrated a wide range in whole-body ²¹⁰Po concentrations with values varying between 38 Bq kg^-1 (wet wt.) in ascidians to 174 Bq kg^-1 wet in starfish. The lowest concentrations (0.37 Bq kg^-1 wet) were found in the muscle of the rattail Coryphaenoides armatus. In mesopelagic fish muscle ²¹⁰Po concentrations ranged from 0.2 Bq kg^-1 wet in Aphanopus carbo to 980 Bq kg^-'1 wet in the hatchet fish Argyropelecus aculeatus. In the hatchet fish a very high concentration of 7.9 kBq kg^-1 wet in gonad results in a dose of 4.2 Sv y^-1 to that organ. In general, the ²¹⁰Po concentrations measured in abyssal and mesopelagic species are similar to those which have been reported for coastal organisms. The large differences in ²¹⁰Po concentrations among similar species inhabiting the same water mass suggests that ²¹⁰Po levels in these organisms arise primarily from the different prey they ingest rather than by direct uptake from water