Abstract. Anoxia was successfully induced in four benthic chambers installed at 24 m depth in the northern Adriatic Sea for periods varying from 9 days to 10 months. During the 10-month period, species richness significantly decreased. Although no significant change in Shannon diversity and evenness was observed, the composition of the foraminiferal assemblages changed with time. This change is due to interspecific differences in tolerance to anoxia. Reophax nanus, Textularia agglutinans and Quinqueloculina stelligera all showed a significant decrease with time, strongly suggesting they are sensitive to anoxia. Conversely, Eggerella scabra, Bulimina marginata, Lagenammina atlantica, Hopkinsina pacifica and Bolivina pseudoplicata appeared to be resistant to the experimental conditions. Quinqueloculina seminula was apparently sensitive to anoxia but showed a clear standing stock increase during the first month of the experiment, which we interpret as an opportunistic response to increasing organic matter availability due to the degradation of the dead macrofaunal organisms. None of the anoxia-sensitive species is able to accumulate intracellular nitrates. Nitrate accumulation could be shown for some tested specimens of the dominant anoxia-tolerant species E. scabra and B. marginata. However, tests on the denitrification capacity of these taxa yielded negative results, suggesting that their resistance to long-term anoxia is not due to their ability to denitrify.
Abstract. Hard-shelled foraminifera are protists able to build a calcareous or agglutinated shell (called a “test”). Here we study the impact of sediment acidification on calcareous test preservation. For this study, sediment cores were sampled in the macrotidal Auray estuary located on the French Atlantic coast. Living and dead foraminifera were quantified until 5 cm depth and discriminated using the Cell-Tracker™ Green vital marker. The pH and oxygen profiles combined with quantitative polymerase chain reaction (qPCR) suggested that cable bacteria were most likely to cause the acidifying process. Cable bacteria (CB) are filamentous bacteria coupling sulfide oxidation to oxygen reduction over centimetre distances, generating a strong pH gradient within the first few centimetres of the sediment that could affect the microhabitats occupied by benthic foraminifera. On two different intertidal mudflats, volumetric filament densities have been estimated. They were comparable to those observed in the literature for coastal environments, with 7.4 ± 0.4 and 74.4 ± 5.0 m cm−3 per bulk sediment, respectively. Highly contrasting sediment acidification (from low to very intense) was described from 1.0 to 2.4 ΔpH. This seems to lead to various dissolution stages of the foraminiferal calcareous test from intact to fully dissolved tests revealing the organic lining. The dissolution scale is based on observations of living Ammonia spp. and Haynesina germanica specimens under a scanning electronic microscope. Furthermore, dead foraminiferal assemblages showed a strong calcareous test loss and an organic lining accumulation throughout depth under low pH, hampering the test preservation in deep sediment. These changes in both living and dead foraminiferal assemblages suggest that cable bacteria must be considered in ecological monitoring and historical studies using foraminifera as bioindicators and paleoenvironmental proxies.
Research Article| July 01, 2009 REPRODUCTION AND GROWTH OF THE DEEP-SEA BENTHIC FORAMINIFER BULIMINA MARGINATA UNDER DIFFERENT LABORATORY CONDITIONS Christine Barras; Christine Barras 3 1Laboratory of Recent and Fossil Bio-Indicators (BIAF), UPRES EA 2644, Angers University, France, and Laboratory of Marine Bio-Indicators (LEBIM), Ile d’Yeu, France2Laboratoire des Sciences du Climat et de l’Environnement (LSCE), CEA-CNRS-UVSQ, Gif-sur-Yvette, France 3Correspondence author: Current address is Laboratory of Recent and Fossil Bio-Indicators (BIAF), UFR Sciences -2, Boulevard Lavoisier, 49045 Angers Cedex 01 -France. E-mail: christine.barras@univ-angers.fr Search for other works by this author on: GSW Google Scholar Emmanuelle Geslin; Emmanuelle Geslin 1Laboratory of Recent and Fossil Bio-Indicators (BIAF), UPRES EA 2644, Angers University, France, and Laboratory of Marine Bio-Indicators (LEBIM), Ile d’Yeu, France Search for other works by this author on: GSW Google Scholar Jean-Claude Duplessy; Jean-Claude Duplessy 2Laboratoire des Sciences du Climat et de l’Environnement (LSCE), CEA-CNRS-UVSQ, Gif-sur-Yvette, France Search for other works by this author on: GSW Google Scholar Frans J. Jorissen Frans J. Jorissen 1Laboratory of Recent and Fossil Bio-Indicators (BIAF), UPRES EA 2644, Angers University, France, and Laboratory of Marine Bio-Indicators (LEBIM), Ile d’Yeu, France Search for other works by this author on: GSW Google Scholar Journal of Foraminiferal Research (2009) 39 (3): 155–165. https://doi.org/10.2113/gsjfr.39.3.155 Article history received: 08 Oct 2008 accepted: 30 Mar 2009 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Christine Barras, Emmanuelle Geslin, Jean-Claude Duplessy, Frans J. Jorissen; REPRODUCTION AND GROWTH OF THE DEEP-SEA BENTHIC FORAMINIFER BULIMINA MARGINATA UNDER DIFFERENT LABORATORY CONDITIONS. Journal of Foraminiferal Research 2009;; 39 (3): 155–165. doi: https://doi.org/10.2113/gsjfr.39.3.155 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract In this study, laboratory experiments were performed to investigate the impact of different food types and temperatures on the reproduction and growth of the benthic foraminifer Bulimina marginata. To study reproductive success, adult specimens were kept alive at 6, 8, 10, 12, and 14° C, and fed with either freeze-dried green algae or live diatoms. The effects of temperature, food type, and food quantity on test growth rate were studied under different combinations of these parameters. Lower temperature delayed reproduction, resulted in fewer offspring, and decreased growth rate. Fresh food produced better results than freeze-dried food probably because the latter reduces the amount of digestible compounds (carbohydrates and polyunsaturated fatty acids). In order to obtain reproduction and growth of the open marine species B. marginata in a limited period of time, we recommend keeping them at a temperature ranging 8–12° C (approximating their in situ temperature), and to feed them with fresh algae. The results of this study should be useful to researchers who wish to set up experiments that require culturing deep-sea foraminifera. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
