Foraminiferos Bentonicos Del Talud Continental Desde Concepcion a Las Islas Guaitecas (36º- 44° S), Chile (Foraminifera: Lagenina, Miliolina Y Robertinina)

Living (rose Bengal stained) benthic foraminifera were investigated on surface sediments from 23 stations from the river-dominated northwestern Portuguese margin. Samples were collected in March 2011, following the period of the maximum rainfall over the Iberian Peninsula, between 20 and 2000 m water depth along five cross-margin transects. Four of them are located off the Douro, Mondego, Tagus, and Sado Rivers and one off the Estremadura coast. The major objectives of this study are (1) to assess the impact of organic matter of various origin and quality on the benthic foraminifera and (2) to investigate the spatial differences of faunal distribution from coastal waters to the deep sea under river influences. To do this, sedimentological and biogeochemical characteristics of the sediments were identified by measuring grain size, oxygen penetration depth, total organic carbon (TOC) content, stable carbon isotopic composition of TOC (δ 13 C TOC ) and concentration of pigments and amino acids. Based on the principal component and cluster analyses of the environmental data, three major geographical groups are identified: (1) deep stations, (2) coastal and middle slope stations, and (3) shelf stations under river influence. At the deepest stations, species are associated with high organic matter (OM) quantity but low OM quality, where Uvigerina mediterranea, Hoeglundina elegans, and agglutinated species such as Reophax scorpiurus or Bigenerina nodosaria are dominant. All stations off the Sado River, which is the most affected area by the anthropogenic influence, are also characterized by high quantity but low quality of OM with the minimum faunal density and diversity within the study area. Middle slope stations are associated with low OM content and coarse sediments (Q 50 ) with the predominance of N. scaphum. Shallow shelf stations close to the Douro and Tagus River mouths show a dominance of taxa (e.g., Ammonia beccarii, Bulimina aculeata, Eggerelloides scaber, Nonion scaphum, Cancris auriculus, and Quinqueloculina seminula) adapted to environments characterized by high OM quality (high fresh chlorophyll (Chl a/Phaeo)) and available amino acids (enzymatically hydrolyzable amino acid (EHAA)/total enzymatically hydrolyzable amino acid (THAA)). The Biotic and Environmental linking analysis suggests that the benthic foraminiferal distribution is mostly controlled by three environmental parameters, i.e., TOC (quantity), EHAA/THAA (quality), and δ 13 C TOC (source). Hence, this study clearly highlights that the quantitative and qualitative inputs of OM and its source are the most important factors controlling the living benthic foraminiferal distribution with clear influences between the different rivers. This study also suggests a good tolerance of several species for river discharges where the OM quality is high.

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Impact of organic matter source and quality on living benthic foraminiferal distribution on a river‐dominated continental margin: A study of the Portuguese margin

Dessandier

Bonnin

Kim

et al. 2016

JGR Biogeosciences

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Spatial and Vertical Benthic Foraminifera Diversity in the Oxygen Minimum Zone of Mejillones Bay, Northern Chile

et al. 2022

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Mejillones Bay is located in northern Chile (23°S) and is influenced by an Oxygen Minimum Zone (OMZ), with oxygen levels below 0.5 ml l–1. This area presents particular ecological characteristics, such as circulation of currents, hotspot, high productivity and industrial activity. This extreme ecosystem generates the need to understand their dynamics and changes across time and space, as well as to identify the main differences with other OMZs. For this reason, we studied the benthic foraminifera to use them as environmental and oxygenation proxies. For this purpose, two sediment cores (ZA and Z1A) were collected, obtaining 14 samples of the first 8 cm (vertical distribution), and 18 samples with a mini boxcore (spatial distribution). When analyzing the foraminifera community, some similarities were found in environmental characteristics of other OMZs, such as the predominance of Bolivina seminuda, Bolivina costata, Epistominella exigua, Fursenkoina sp., and Nonioella stella (species typical of hypoxic conditions). In addition, a high abundance of angular-asymmetric morphologies was observed, indicating eutrophied silty substrates and low current circulation. However, the Mejillones Bay recorded a particular spatial and vertical dynamics respect to others OMZs, due to presence of other species of Bolivinids not reported for this area before, and a high abundance of Buliminella elegantissima, which is not recorded in most of OMZs. Foraminifera with rounded-symmetric morphologies were present and dominant in deeper layers, reflecting a turbulent and high-energy environment. On the basis of depth and conditions of microxia or dysoxia, no significative pattern of spatial and vertical distribution was observed. The latter can be explained by local factors such as cyclonic and anticyclonic whirlpools, wastewater from industrial activity and natural disaster such a Tsunami occurred in 1877. These factors contributed to the mixture of the benthic foraminifera and prevented the formation of spatial and vertical patterns. Finally, an intensification of hypoxia was identified, indicating microxia (0,01 ml l–1) in the superficial layers (0–3 cm from years 1996 to 2012), while the deeper layers (4–8 cm from years 1985 to 1877) presented foraminiferal species that indicated dysoxia conditions (0,07 ml l–1). The latter differs from other OMZs, which show greater oxygenation in the most superficial layers and microxia in deeper layers. This study represents the first ecological reconstruction using benthic foraminifera proxies for the Mejillones Bay, which results indicate an OMZ with ecological and environmental features that differ from other OMZs.

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Catálogo de los tipos depositados en las colecciones zoológicas de la Universidad de Concepción (MZUC-UCCC) entre diciembre de 1992 y agosto de 2015

Artigas¹,

Solar²

2015

Gayana (Concepc.)

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Foraminiferos Bentonicos Del Talud Continental Desde Concepcion a Las Islas Guaitecas (36º- 44° S), Chile (Foraminifera: Lagenina, Miliolina Y Robertinina)

Cited by 3 publications

References 4 publications

Impact of organic matter source and quality on living benthic foraminiferal distribution on a river‐dominated continental margin: A study of the Portuguese margin

Impact of organic matter source and quality on living benthic foraminiferal distribution on a river‐dominated continental margin: A study of the Portuguese margin

Spatial and Vertical Benthic Foraminifera Diversity in the Oxygen Minimum Zone of Mejillones Bay, Northern Chile

Catálogo de los tipos depositados en las colecciones zoológicas de la Universidad de Concepción (MZUC-UCCC) entre diciembre de 1992 y agosto de 2015

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