Lateral and vertical distributions of living benthic foraminifera off the Douro River (western Iberian margin): Impact of the organic matter quality
Dessandier, P.-A.; Bonnin, J.; Kim, J.-H.; Bichona, S.; Grémare, A.; Deflandre, B.; de Stigter, H.; Malaizé, B. (2015). Lateral and vertical distributions of living benthic foraminifera off the Douro River (western Iberian margin): Impact of the organic matter quality. Mar. Micropaleontol. 120: 31–45. dx.doi.org/10.1016/j.marmicro.2015.09.002 In: Marine Micropaleontology. Elsevier: Amsterdam; New York; Oxford; Tokyo. ISSN 0377-8398; e-ISSN 1872-6186, more |  |
| Keyword | | | Author keywords | Living benthic foraminifera; Organic matter; Douro River; Portuguese margin |
| Authors | | Top | - Dessandier, P.-A.
- Bonnin, J.
- Kim, J.-H., more
- Bichona, S.
| - Grémare, A., more
- Deflandre, B.
- de Stigter, H., more
- Malaizé, B.
| |
| Abstract | In this study,weassess the impact of the quantity and quality of the organicmatter on the distribution of live benthicforaminifera on a cross-margin transect off the Douro River (western Iberian margin). Surface sedimentsfrom five stations ranging from 50 to 2000mwater depth were collected in March 2011 at the end of the periodof maximal river runoff, in order to better evaluate the importance of terrestrial input. Living (stained) benthicforaminiferal assemblages (N150 µm) and environmental parameters (grain size, total organic carbon (TOC),total nitrogen (TN), C/N ratio, d13CTOC, pigments andamino acids)were investigated. Organic matter amounts followthesediment grain size pattern with higher concentration in fine sediments and seem to control faunal density,except at the shallowest station where TOC is low and faunal density high. At this coastal site, a massivesandy deposit is identified and associated with very low faunal diversity. Labile organic matter is richest at theshelf stations where benthic foraminifera standing stocks are high. This is particularly evident on the Douromud patch where both density and diversity are high. Foraminiferal faunas living at the shelf stations are dominatedby species (e.g., Nonion scaphum, Ammonia beccari,i Bulimina aculeata and Eggerella scabra) characteristicof the rich trophic conditions, with organic matter of mixed estuarine and marine origin. Very low total standingstocks on the upper slope are associatedwith coarse sediments, probably resulting from intense bottomcurrentsat this depth resulting in poor trophic conditions. Deeper environments are characterized by species(e.g., Hoeglundina elegans, Uvigerina mediterranea and Reophax scorpiurus) indicative of fairly abundant butlow-quality organic matter. Finally, the faunal differences between the shelf stations may reflect different successionalstages: an early stage at 50mwater depthwhere unstable conditions are observed,with faunas dominatedby opportunistic species and a more mature fauna in the mud patch where more stable conditions prevail. |
|
