Distribution Patterns Of Foraminifera Research Articles

Calcareous assemblages of the southeastern Mediterranean low-tide estuaries — Seasonal dynamics and paleo-environmental implications

The study of estuarine ecosystems is essential for protecting and reestablishing their threatened biota. In this research the spatio-temporal variations in the distribution patterns of foraminifera, ostracods and molluscs are analyzed in surficial sediments sampled in 2012/13 at six low-tide estuaries of the southeastern Mediterranean coast. Live assemblages are studied using multivariate statistical analyses to determine their ecological preferences and seasonal dynamics whereas the dead assemblages are used to establish a reference baseline for future paleoenvironmental reconstruction.The statistical analysis indicates that salinity, TOC and % carbonate are the main environmental factors explaining 60% of the cumulative variance and controlling the distribution pattern of the different brackish taxa encountered in these estuaries. The foraminifera Ammonia tepida and some miliolids (Quinqueloculina and Varidentella) inhabit most estuaries during summer when salinities of 13–18psu and temperatures of 26–34°C occur. At the Naaman stream the agglutinated species Birsteiniolla macrostoma and Trichohyalus aguayoi dominate the assemblage during autumn and winter, respectively when salinities of 3–7psu and temperature of 18–24°C prevail. High abundance of the monospecific assemblage of the ostracod Cyprideis torosa was encountered at the Tanninim year round in oligohaline water. The gastropod Heleobia phaeniciaca prefers living at the Naaman and Tanninim streams while Pyrgophorus sp., an invasive and low salinity species, continue colonizing more stream reaches along the Israeli coast.The dead assemblages are composed of high numbers of local and transported species. It includes post storm-surge sediments containing high numbers of inland fresh and brackish water species transported by the floods. Those are mixed with inner to mid-shelf benthic and planktonic foraminifera, ostracods and molluscs. Transportation of the marine organisms a few hundred of meters inland via the estuaries indicates that the coastal areas are prone to storm surge events that are preserved clearly on the coast.The present study demonstrates that the combined use of different multi-proxy faunal records enhances significantly the understanding of the dynamics of low-tide estuaries. This can be applied also to other low-tide estuaries worldwide and facilitate better management of these threatened environments. Additionally, it enables understanding of the post-mortem processes that control the transition from the living to the death assemblages and by that improve paleoenvironmental reconstruction of the lower reaches of low-tide estuaries.

Planktic foraminifera from the mid-Cretaceous (Barremian–Early Albian) of the North Sea Basin: Palaeoecological and palaeoceanographic implications

A marine Cretaceous succession (Barremian–Albian) of a cored borehole (BGS 81/40), located in the Central North Sea Basin, has been examined with respect to its planktic and benthic foraminiferal content, as well as for calcareous nannofossils. The distribution patterns of foraminifera and calcareous nannofossils allow for a two fold division of the investigated interval. (1) The Barremian–earliest Aptian interval, which reflects a marine, temporary restricted setting. This is indicated by sporadic occurrences of planktic foraminifera with very rare planispiral forms suggesting short-term connections of the Boreal and Tethyan Realms. The benthic foraminiferal assemblages indicate aerobic, sometimes dysaerobic bottom-water conditions. High abundances of nannoconids in the Barremian suggest enhanced stratification and/or warm, oligotrophic surface water. (2) The late Aptian–early Albian interval, which was characterised by an open-oceanic environment with cool and aerobic surface water conditions. Planktic foraminifera are more abundant and diverse than in the lower interval. Trochospiral hedbergellids dominate the foraminiferal assemblages. The episodic occurrences of planispiral, clavate and trochospiral-flattened planktic morphotypes indicate the existence of a seaway between the Boreal and the Tethyan Realms. Aerobic to dysaerobic bottom-water conditions are suggested by the composition of the benthic foraminiferal assemblages. High abundances of cool-water taxa within the calcareous nannofossil assemblages indicate a cooling trend across the latest Aptian and earliest Albian.

HYDRODYNAMIC CIRCULATION IN THE ESTUARIES OF ESTACAO ECOLOGICA JUREIA-ITATINS, BRAZIL, INFERRED FROM FORAMINIFERA AND THECAMOEBIAN ASSEMBLAGES

Research Article| January 01, 2003 HYDRODYNAMIC CIRCULATION IN THE ESTUARIES OF ESTAÇÃO ECOLÓGICA JURÉIA-ITATINS, BRAZIL, INFERRED FROM FORAMINIFERA AND THECAMOEBIAN ASSEMBLAGES Wânia Duleba; Wânia Duleba 1Departamento de Geologia Sedimentar e Ambiental, Instituto de Geociências, Universidade de São Paulo, 05508-080 São Paulo, SP, Brazil. E-mail: waduleba@uol.com.br Search for other works by this author on: GSW Google Scholar Jean-Pierre Debenay Jean-Pierre Debenay 2Université d’Angers, Laboratoire de Géologie and LEBIM (Laboratoire d’Etude des Bio-Indicateurs Marins), île d’Yeu, France. E-mail: debenay@univangers.fr Search for other works by this author on: GSW Google Scholar Journal of Foraminiferal Research (2003) 33 (1): 62–93. https://doi.org/10.2113/0330062 Article history received: 18 Jun 2001 accepted: 16 Jan 2002 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Wânia Duleba, Jean-Pierre Debenay; HYDRODYNAMIC CIRCULATION IN THE ESTUARIES OF ESTAÇÃO ECOLÓGICA JURÉIA-ITATINS, BRAZIL, INFERRED FROM FORAMINIFERA AND THECAMOEBIAN ASSEMBLAGES. Journal of Foraminiferal Research 2003;; 33 (1): 62–93. doi: https://doi.org/10.2113/0330062 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 Depth measurements and chemical, sedimentological and microfaunal analyses were conducted in two microtidal estuaries, devoid of anthropogenic pollution, in the ecological reserve of Juréia-Itatins (E.E.J.I.). The spatial and temporal (summer and winter) variations in the composition of foraminifera and thecamoebian assemblages relative to hydrographic and sedimentological parameters were studied and compared with microfaunal data from other estuarine areas. Canonical correspondence analysis (CCA) was used to assess the relationship between microfaunal and abiotic variables. The distribution patterns of foraminifera and thecamoebians corresponded most strongly to bottom salinity and bottom temperature. The species distribution in the microtidal estuaries of E.E.J.I. was similar to that reported from macrotidal estuaries (Argentine and temperate regions) but differed from that observed in other tropical and subtropical microtidal estuaries of Brazilian and African coasts. Distribution patterns of foraminiferal and the-camoebian assemblages facilitated the development of hydrodynamic models of water circulation in the two estuaries. Such modeling would have been very difficult using only hydrological and chemical data because of the complex and highly variable water circulation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Synergetic influence of water masses and Kangaroo Island barrier on foraminiferal distribution, Lincoln and Lacepede shelves, South Australia: A synthesis

The mid-latitude, cool-water, high-energy Lincoln and Lacepede Shelves along the southern Australian margin are covered with mixed Holocene and Pleistocene sediments. Foraminiferal specimens of Recent and Pleistocene age from dredge samples are strongly mixed. Eight assemblages in two major groups A and B were recognised from the inner shelf to the upper slope, and they appear to be depth-related. However, some are typical of localised environments such as an upwelling zone (assemblage A2) or areas strongly affected by a high accumulation of relict specimens indicative of previous lagoonal deposition (assemblages A3 and A4). Sediment starvation due to strong wave abrasion is largely responsible for the preservation of this mixed biofacies. The interaction between shelf waters (the Great Australian Bight Current), waters from the Spencer and St. Vincent Gulfs, oceanic waters and waters from the River Murray, is suggested as the main factor controlling the overall distribution pattern of foraminifera. A warmer, nearly oligotrophic condition on the Lincoln Shelf, signalling a warmer regime, is indicated by a higher abundance of warmwater planktonic species and by a higher faunal diversity. On the Lacepede Shelf, the diversity is lower and warm-water forms are less common, implying a cooler or mesotrophic condition. These differences may be due to the position of Kangaroo Island which blocks the passage of the shelf water flowing to the southeast, thereby creating two different water regimes. This barrier would have been more significant during the late Pleistocene, when sealevel was low, the shelves were narrower and a lagoonal environment was present as indicated by different relict faunas on these two shelves.

Distribution of living benthic Foraminifera on the back-reef and outer slopes of a high island (Moorea French Polynesia)

Living foraminifera were examined on both sides of the barrier reef across a section situated on the north-west part of the high island of Moorea (Society Archipelago, French Polynesia). In all, 87 species were found: 62 in the back-reef area (fringing reef, channel and barrier reef) and 72 on the outer slope; 47 were common to both zones. This study points out the importance of substrates in the distribution pattern of foraminifera. The sediments are essentially inhabited by epipsammitic species, whereas algae are colonized mainly by free-living foraminifera: miliolids in the back-reef area; rotaliids in the outer slope. Free-living individuals are much less abundant in the fringing reef, channel and inner part of the barrier reef than in the other parts of the study area. The two major groups on the two sides of the barrier reef are very different in size, test building and probably nutritional modes. In the back-reef area, epipsammitic taxa, mainly composed of small agglutinated species, dominate the fauna; in the outer slope large calcareous symbiotic Amphistegina are the major components of the living association (50 to 70%).