Figure 1.

(a) Location map of the Main Endeavour Field (Juan de Fuca Ridge, northeast Pacific) indicating the positions of hydrothermal vent edifices, with (b) a visualization of the three-dimensional topographic structure of Grotto. The yellow dot on Grotto represents the position of TEMPO-mini. The distances and heights were estimated using COVIS (Cabled Observatory Vent-Imaging Sonar). (c) Deployed instruments: I = remote access sampler (RAS); II = assemblage filmed by the camera; III = benthic and resistivity sensors (BARS); IV = Aanderaa optode; V = TEMPO-mini; VI = thermistor chain (T-chain) and VII = autonomous temperature loggers (F-probes).