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Testate rhizopod growth and mineral deposition on experimental substrates from Cross Seamount

Authors
Journal
Deep Sea Research Part I Oceanographic Research Papers
0967-0637
Publisher
Elsevier
Publication Date
Volume
41
Issue
3
Identifiers
DOI: 10.1016/0967-0637(94)90096-5
Disciplines
  • Design

Abstract

Abstract We present the results of an experiment on Cross Seamount (18°40′N, 158°17′W) in which basalt, ferromanganese-oxide and CaCO 3 substrates were deployed for 19 months. An experimental block design, of identical sets of well-characterized substrates arranged on three distinct panels, was used. Alterations resulting from exposure at 800 m water depth were documented by analytical Scanning Electron Microscopy. Agglutinated rhizopods and irregularly shaped chambers occupied an average of 37% of the basalt surfaces, and 13 and 20% of the ferromanganese-oxide and CaCO 3 substrates, respectively. This coverage is high, relative to that observed on dredged ferromanganese nodules and crusts. High coverage can be attributed to the low abundance of other agglutinated and calcareous foraminifera. Metal-rich deposits composed of BaS, AlSi, Mn and Fe were common on substrate surfaces. Barite (BaS) particles, which originated in the water column, were observed attached to the substrate by agglutinated foraminiferal tests. Fe-enriched AlSi deposits were often adhered to the substrate. These deposits appeared to have been produced by benthic rhizopods, and may persist on the seafloor over time. Fe-coated bacteria-like colonies were numerically scarce, but covered large areas. Mn-oxide precipitates, also bacteria-like, were numerically abundant on ferromanganese-oxide substrates, but never observed on other substrates. The occurrence and morphological features of these Fe- and Mn-oxide coatings reinforce the idea that bacteria play an important role in the accretion of ferromanganese-oxides on the seafloor.

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