Indurated sediment from the apron and basal areas of hydrothermal mounds in Middle Valley, on the Juan de Fuca Ridge, northeastern Pacific Ocean, is the site of attachment for a variety of encrusting agglutinated foraminifera. Hydrothermal venting in Middle Valley has created a unique environment which is characterized by elevated temperatures of substrate and bottom water, low pH values, and consolidated substrate. Foraminifera avoid areas in direct contact with the extremely high temperatures of hydrothermal vent fluids, but encrust the surrounding indurated sediment. Species diversity is low and population density varies on a small scale. One new genus, Ropostrum, with its type species R. amuleturn, is described from this locality. The substrate bears other micro-organisms of unknown affinity which are illustrated here. A comparison with other deep-sea consolidated substrates shows that encrusting agglutinated foraminifera prefer Fe-and Mn-rich surfaces.

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Journal Journal of Foraminiferal Research
Jonasson, K.E. (K. E.), & Schroder-Adams, C. (1996). Encrusting agglutinated foraminifera on indurated sediment at a hydrothermal venting area on the Juan de Fuca Ridge, northeast Pacific Ocean. Journal of Foraminiferal Research, 26(2), 137–149. doi:10.2113/gsjfr.26.2.137