Species Of Larger Benthic Foraminifera Research Articles

Microfacies types (MFT) and palaeoenvironment of the Umlatodoh carbonates in the Shillong Plateau of Meghalaya, NE India

One of the major marine transgressions in the Shillong Plateau is represented by the middlemost Umlatodoh Formation of the Sylhet Limestone Group during early Eocene. Based on 26 species of Larger Benthic Foraminifera (LBF) and eleven species of calcareous red algae and green algae, nine Tethyan MFT (microfacies types) viz, Miliolid Packstone-Grainstone, Algal Packstone-Grainstone, Miliolid Grainstone, Larger Benthic Foraminiferal Grainstone, Green Algae Grainstone, Alveolina oblonga Grainstone, Oolitic Packstone-Grainstone and Micrite have been identified for the Umlatodoh Limestone. These microfacies have contributed towards identification of a range of environments from low-energy, shallow neritic inner-shelf through shallow, reef shelf to more restricted environment represented by pure micrite. Petrographical characteristics indicate that these limestones are primarily microcrystalline allochemical rocks of biomicritic type and a mixture of packstone and grainstone. The foraminiferal assemblage associated with various species of coralline red algae and green algae suggests inner ramp, mud-free shallow neritic shelf carbonate sedimentation of the Umlatodoh Limestone showing depositions in calm water, low-energy conditions in the lower part changing to moderately high-energy conditions in the middle followed by low-energy restricted environment represented by micrite towards the upper part.

Using larger benthic foraminifera for the paleogeographic reconstruction of Neo-Tethys during Paleogene

The biostratigraphic range distribution of larger benthic foraminifera (LBF) from the eastern part of Neo-Tethys in the Kohat Basin of Pakistan is compared with the Western and Central Neo-Tethys. The results are used to establish the migration pathways of LBF for the paleogeographic reconstruction of the Neo-Tethys that existed in the Paleogene. This comparison across the Neo-Tethys revealed that LBF species are mostly confined to the Gondwanan (Iran, Iraq, Pakistan, India, Indonesia) and Laurasian-derived blocks (Italy, France, and Spain), with only a few on the margin of the Gondwanan continents (Oman).

Neorotalia omanensis and Operculina musawaensis from the Sultanate of Oman

Two new species of larger benthic foraminifera, Neorotalia omanensis n. sp. and Operculina musawaensis n. sp. are described and illustrated from the eastern Oman Mountains. N. omanensis n. sp. occurs in the Musawa Formation in association with the planktonic foraminifera Morozovella edgari and Truncarotaloides topilensis indicating an early to middle Eocene age (P10-P13). Operculina musawaensis n. sp. occurs in the Abat Formation in association with the planktonic foraminifera Acarinina esnaensis and A. soldadensis indicating an early Eocene age (P6). This is the first known record showing the presence of genus Neorotalia in the Middle East. Representatives of the larger foraminiferal genus Linderina sp. are also described and illustrated from the Musawa Formation and compared with the published Linderina species in the surrounding countries.

Revision in the paleontology and distribution of the larger benthic foraminifera in the Oligocene–Miocene deposits of the Zagros Basin, southwest Iran

The present research is a revision in the distribution and description of the larger benthic foraminifera from the Oligocene–Miocene Asmari Formation in the Zagros Basin in southwest Iran. From the shallow marine carbonates of the Asmari Formation, 21 genera and 41 species of larger benthic foraminifera have been identified of which 22 species have been described in recent research. The described genera belong to 11 families. The recognised foraminifera includes Nummulites, Operculina, Heterostegina, Spiroclypeus, Nephrolepidina, Eulepidina, Neorotalia, Amphistegina, Victoriella, Carpenteria, Planorbulinella, Miniacina, Planorbulinoides, Austrotrillina, Archaias, Praearchaias, Praerhapydionina, Peneroplis, Spirolina, Miogypsinoides, Meandropsin and Borelis. On the basis of the distribution of the larger benthic foraminifera, five assemblage biozones have been recorded in the Asmari Formation in the study area. The foraminifers' assemblages indicate to Oligocene (Rupelian and Chattian stages) and lower Miocene (Aquitanian and Burdigalian stages) times. There is a similarity of the Mediterranean and Indo-West Pacific fauna with the Asmari Formation fauna in the Rupelian–Chattian times. On the basis of the dissimilarity distribution of larger benthic foraminifera, there was no connection seaway between the shallow marine limestone of the Asmari Formation and Indo-West Pacific region in the Aquitanian and Burdigalian times. http://zoobank.org/9F01EBBD-1EE4-47EA-B51B-D03B279A7D59

Mixing of relict and modern tests of larger benthic foraminifera on the Great Barrier Reef shelf margin

The distribution of live, well preserved, and relict larger benthic foraminifera (LBF) in sediment samples collected off the shelf margin near Hydrographers Passage in the Great Barrier Reef, Australia, was studied to document taphonomic processes in this setting. In total, eight living species of LBF were found, mostly of the families Amphisteginidae and Nummulitidae, separated into a shallow (platform) assemblage and a deep (terrace) assemblage. The modern (well preserved) shells in the sediment revealed a good representation of this fauna, but differences in depth distribution were lost. The relict fauna is represented by a more diverse fauna, and is composed mostly of taxa occurring in much shallower conditions. We interpret this pattern as an initial downslope transport of the foraminifera from the shelf into deeper waters, and a mixing of foraminifera derived from nearby Pleistocene coral reef structures.

Temperature‐induced stress leads to bleaching in larger benthic foraminifera hosting endosymbiotic diatoms

Physiological mechanisms of bleaching were studied on larger benthic foraminifera (LBF) hosting endosymbiotic diatoms. Amphistegina radiata, Heterostegina depressa, and Calcarina hispida were exposed to increasing temperatures in static temperature experiments (23°C to 33°C, 6 d). Photosynthetic activity (Fv : Fm, measured with a pulse‐amplitude modulated fluorometer), chlorophyll a (a proxy for symbiont biomass), and motility (a proxy for overall fitness of the foraminifera) were reduced in specimens at 32°C to 33°C, and cytoplasm color changes associated with bleaching were observed. A 30‐d flow‐through experiment at three temperatures (26°C to 31°C) and three levels of inorganic nitrate concentration (0.5 to 1.4 µmol L−1) confirmed negative effects of temperature at 31°C for A. radiata (including growth) and H. depressa. Another Calcarina species, Calcarina mayorii, was not affected. This suggests that temperature effects are species‐specific. However, elevated nutrient concentrations did not affect any of the parameters measured. Temperatures > 30°C stress the foram–diatom endosymbiosis in some LBF species, which may lead to subsequent bleaching of the host. Given that a 2–3°C increase led to rapid bleaching of most species, we propose that, similar to corals, these species are threatened by sea‐surface temperature increase predicted for tropical reef waters in the near future.

ORGANIC AND INORGANIC CARBON PRODUCTION BY ALGAL SYMBIONT-BEARING FORAMINIFERA ON NORTHWEST PACIFIC CORAL-REEF FLATS

Algal symbiont-bearing benthic foraminifera are producers of both organic and inorganic carbon in coral-reef ecosystems. However, their contribution to the total budget of reef carbon production has not been adequately quantified. We used O 2 -respirometry and alkalinity-anomaly techniques to estimate the organic and inorganic carbon production rates of three species of symbiont-bearing large foraminifera common to coral reef flats in the northwest Pacific Ocean. The species studied were Baculogypsina sphaerulata and Calcarina gaudichaudii , which both harbor diatom endosymbionts, and Marginopora kudakajimensis , which harbors dinoflagellate endosymbionts. Live mature individuals were placed onto mesh in clear airtight containers filled with filtered seawater. The containers were incubated for several hours at a constant temperature and subjected to different levels of light intensity. Seawater was continuously mixed throughout the experiment. Dissolved oxygen, pH and total alkalinity were measured before and after incubation. Three species of larger benthic foraminifera were net organic and inorganic carbon producers. The P/R ratio exceeded 1 for all species. No photoinhibition was observed up to 1500 μmol photons m −2 s −1 , and calcification was enhanced by light. These findings suggest that the three species are net carbon producers adapted to high-light, reef-flat environments. In addition, we calculated that Baculogypsina sphaerulata and C. gaudichaudii together accounted for 2–7.5% of the gross primary production of a reef-crest community, whereas M. kudakajimensis supplied 1–11% of the gross primary production of a backreef community. The two calcarinids and M. kudakajimensis contributed ~1 and 10% of the inorganic carbon production of seaward reef flat and protected lagoon communities, respectively. Together with previous reports, these estimates suggest that algal symbiont-bearing foraminifera play a minor but essential role in the organic and inorganic carbon production of coral-reef ecosystems.