Ammonia Beccarii Research Articles

Benthic foraminifer Ammonia beccarii as a proxy for paleoproductivity changes from West coast of India

We examined three hundred sixty-five (365) sediment subsamples for benthic foraminifera from beach cores sediment in the west coast of India. The study on the recent benthic foraminiferal faunal record, reveals the paleoecological preferences. A total of 38 species belonging to 22 genera were identified from the study. For benthic foraminiferal faunal study, dry samples were sieved over 125 μm-size sieve and split into suitable aliquots to obtain ~250 specimens of benthic foraminiferal species identified and counted. Ammonia beccarii was the most prevalent species found in all subsamples. The high productivity species of Ammonia beccarii can be found in sediments from Puthenthoodu beach ~75 to 60cm and 10 to 5cm depth, from Chellanam beach sediments 100 to 70cm and 30 to 5cm depth, from Azheekal beach sediments around 90 to 70cm and 18 to 5cm depth, 100 to 80cm and 20 to 5cm depth in Anthakaranazhi beach sediments, an indicates of shallow-marine environment. The species of Ammonia beccarii were utilized for biostratigraphy for several years and have also been confirmed very constructive in paleoceanographic and paleoclimatological reconstruction.

Benthic foraminiferal assemblages in the coastal zone of the yellow river delta: Environmental significance and characteristics of microbial diversity

Unicellular eukaryotes known as benthic foraminifera have sophisticated survival mechanisms and ecological environmental indicators. Ten surface samples from the Yellow River Delta's coastal region were taken for this study to analyze the distribution of foraminifera in relation to environmental factors and to examine their microbial diversity. We looked at the physicochemical aspects of the environment at each sampling site (such as pH, TN, TOC, EC, δ13C, δ15N, PAHs, etc.), and we employed 16S rRNA high-throughput sequencing analysis to look into the interactions between microbial communities and foraminiferal species. The findings demonstrated that the Yellow River Delta's advantage benthic foraminiferal species were Quinqueloculina complanata, Ammonia beccarii, and Ammonia aomoriensis, and that TOC and TN were significant determinants of the distribution of benthic foraminiferal communities. PAH enrichment in the coastal zone effects on microbial communities and benthic foraminifera are not yet readily apparent. Sediment organic carbon and nitrogen isotope analysis revealed that marine plankton may be the dominant source of organic matter in the coastal zone sediments in the research area, which was made up of both land-based and marine organic matter. It implies that foraminifera have some environmental indicators, especially when combined with the distributional traits of the benthic foraminiferal assemblages and their considerable association with environmental parameters. The findings revealed that Q. complanata was found in the Yellow River water-affected estuarine coastal zone, A. aomoriensis was significantly influenced by sediment organic matter content and reflected the estuarine and nearshore environments and the combination of Ammonia beccarii-Ammonia aomoriensis-Elphidium excavatum assemblage indicated a semi-open intertidal shallow marine environment. Additionally, benthic foraminifera showed a responsive association with microorganisms, indicating that microbial diversity may be one of the driving forces behind benthic foraminifera's ability to adjust to environmental changes. The findings of this study will open up new avenues for research into the environmental importance of coastal zone ecosystems and for understanding how benthic foraminiferal communities survive.

Reconstruction of the sedimentary environment of Nayband Bay during the last 1600 years; implications for relative sea level and climate change in Northern Persian Gulf

This paper reconstructs the relative sea level (RSL) and palaeoclimate of the northern coasts of the Persian Gulf (PG) during the last 16 centuries using physiochemical and ecological proxies from a radiocarbon-dated sediment core from the Nayband Bay (NB) estuary. The results show that between 1600 and 1150 cal yr BP, the NB was a marine lagoon with high river discharge, indicated by low organic matter content sandy silt sediments, high foraminiferal abundance (7900 tests per 10 cm3), and balanced agglutinated and hyaline taxa. During the Medieval Warm Period, the NB became a shallow lagoon, and consequently, a playa with high eolian input and low river discharge formed in the studied site that extended until 500 cal. yr BP. This condition is indicated by sediment finning trend, elevated magnetic susceptibility in sandy mud sediments, and low foraminiferal frequency dominated by hyaline taxa (mainly opportunist Ammonia beccarii). During the stillstand condition corresponding to 500–250 cal yr BP, the evolution of tidal channels in the area provided a platform for developing the upcoming mangrove habitat. In the last 250 years, RSL in the north of NB dropped enough to create a low-energy intertidal flat sheltered by a sandbar, which allowed mangrove growth. We conclude that the ecological and sedimentological evolution of the shallow marginal NB is mainly driven by eustatic RSL decline superimposed by local uplift. We suggest that the current orbitally-induced increasing insolation trend, enhanced by human-induced global warming, could increase aridity in the PG and the southern Zagros.

Gastrochaenolites as Palaeoenvironmental Information Traps: The Case of the Tholos of La Pastora (Valencina de la Concepción, SW Spain)

ABSTRACT In the Mio-Pliocene calcareous sandstone slabs used as capstones at La Pastora tholos in the Copper Age megasite of Valencina de la Concepción-Castilleja de Guzmán (SW Spain), marine bioerosion structures produced in the 3rd millennium BCE were recognised. In this work, we focus on the perforations made by the lithophage bivalve Petricola lithophaga, called Gastrochaenolites, specifically on its functionality as a ‘trap’ of sediment of the environment where they were produced and of which there are no observable outcrops. The microfaunal content consisting of planktonic and benthic foraminifera as well as ostracods was studied. It was possible to infer the palaeoenvironmental conditions of the place where the slabs were quarried, c. 4700–4600 years ago, which correspond to a wide marine bay. The presence of benthic foraminifera like Astrononium stelligerum, Elphidum crispum, Ammonia beccarii and ostracods like Loxoconcha elliptica and Cytherois fischeri implies that the sector of the bay had a water temperature of no more than 20°C, a bathymetry between 0 and 25 m of depth. Also, episodes of fluvial influence caused a variation in water salinity between 30 and 35‰, attested by the presence of euryhaline species of ostracods from low energy environments and clay substrates, thus confirming estuarine conditions.

Increasing risk of invasions by organisms on marine debris in the Southeast coast of India

Increasing amount of anthropogenic litter in the marine environment has provided an enormous number of substrates for a wide range of marine organisms, thus serving as a potential vector for the transport of fouling organisms. Here, we examined the fouling organisms on different types of stranded litter (plastic, glass, rubber, foam sponge, cloth, metal and wood) on eight beaches along the southeast coast of India. In total, 17 encrusting species belonging to seven phyla (Arthropoda, Bryozoa, Mollusca, Annelida, Cnidaria, Chlorophyta and Foraminifera) were identified on 367 items, with one invasive species, the mussel Mytella strigata, detected. The most common species associated with marine litter were the cosmopolitan bryozoans Jellyella tuberculata (%O = 31.64 %) and J. eburnea (28.61 %), the barnacle species Lepas anserifera (29.97 %), Amphibalanus amphitrite (22.34 %) and Amphibalanus sp. (14.16 %), and the oyster species Saccostrea cucullata (13.62 %) and Magallana bilineata (5.44 %). We also reported the first records on stranded litter of four species: the gastropod species Pirenella cingulata and Umbonium vestiarium, the foraminiferan Ammonia beccarii, and the oyster M. bilineata. This study is thus the first documentation of marine litter as a vector for species dispersal in India, where the production and consumption of plastic rank among the highest in the world. We also highlight the increasing risk of invasions by non-indigenous organisms attached to debris along the southeast coast of India. Comprehensive monitoring efforts are thus needed to elucidate the type of vectors responsible for the arrival of invasive species in this region. Raising awareness and promoting education are vital components in fostering sustainable solutions to combat plastic pollution in the country and globally.

Recent Foraminifera From the Mahanadi River Estuary, East Coast of India

The Mahanadi River estuary (Figure 1) is one of the major estuaries in India and the largest one in the Odisha State. It is situated within latitudes 190 47? and 200 30? N and longitudes 850 33? and 860 49? E. It originates from Amarakantak region of Madhya Pradesh and flows through Madhya Pradesh and Odisha States over a length of 890 kms having a drainage basin of about 1,41,600 sq. kms with a large catchment area. It opens into the Bay of Bengal at Pardeep in Cuttack district. It has a wide opening into the sea at its northeastern end. The tidal stretch extends up to 32 kms from the mouth. The entire area is full of mangrove vegetation together with mud flats traversed by a network of tidal creeks except some portions such as Paradeep and Astaranga mouth regions which are sandy shorelines. The studies on Recent foraminifera in relation to the prevailing ecological parameters such as salinity, temperature, dissolved oxygen, and pH, and sediment characteristics and organic matter content of the sediments have been carried out in the present investigations. These studies can be used to delineate the palaeo-environments which serve as useful tools in the exploration for petroleum. 10 sediment and 10 water samples were collected from the estuary for the study of foraminifera and sediment characters, and water analysis respectively. The foraminifera of the estuary were identified. 12 abundant species which are Ammobaculities exiguus, Ammonia beccarii, Ammonia beccarii tepida, Elphidium advenum, Elphidium hispidulum, Milliamina fusca, Nonion depressulus, Pararotalia nipponica, Pararotalia cf. globosa, Quinqueloquelina lamarckina, Quinqueloculina seminulum and Rosalina globularis and are related to the prevailing ecological parameters and the substrate characteristics including the organic matter content.

Distribution of Foraminiferal Assemblages in Contemporary Bottom Sediments of Qua-Iboe River Estuary, Southeast Nigeria

Abstract Qua-Iboe River estuary, Southeast Nigeria, was studied to determine the relationship between foraminiferal distribution and bottom water physicochemical parameters including salinity, temperature, depth, dissolved oxygen, pH, tidal energy, and sediment. Fifty-five bottom sediment samples from geo-referenced stations were collected at water depths of 0–10 m across the channel. Ten species of foraminifera were identified in the estuary. Q-mode cluster analysis resulted in two biotopes (1 and 2), each representing distinct sub-environments. Biotope 1 included two sub-groups namely, 1a and 1b. Biotope 1a represents the upper estuary environment and is distinguished by the non-recovery of foraminifera. It has a maximum water depth of 8.3 m and occurs in freshwater conditions (0 ppt) with slightly acidic to neutral pH and fine- to medium-grained sands. Biotope 1b is found in the mid-estuarine environment and has a maximum water depth of 4 m. It is distinguished by an abundance of Arenoparrella mexicana. Biotope 2 occurs within the subtidal lower estuarine environment with a maximum water depth of 4 m. It is characterized by slightly acidic to slightly alkaline (pH = 6–8), brackish to marine waters, with fine to very fine-grained sands. Foraminiferal species commonly found in this biotope include Ammonia beccarii, Pseudononion japonicum, and Cribroelphidium excavatum. As salinity increased seawards, agglutinated taxa were gradually replaced by calcareous species. Foraminiferal assemblages in bottom sediments are strongly influenced by salinity.

Assessing the effects of heavy metals and polycyclic aromatic hydrocarbons on benthic foraminifera: The case of Houshui and Yangpu Bays, Hainan Island, China

This work aimed to investigate the distribution of benthic foraminiferal assemblages in Houshui and Yangpu Bays, Hainan Island, and assess the relative effects of heavy metals, total organic carbon (TOC), and polycyclic aromatic hydrocarbons (PAHs) on foraminiferal assemblages. A total of 30 sites were sampled and analyzed for benthic foraminiferal assemblages, heavy metals, TOC, and PAHs. The organic matter in the study was derived primarily from algae according to the C/N ratios, and PAHs were generated by petroleum and combustion of petroleum products, as inferred from the diagnostic ratios of PAH isomers. Two-way hierarchical cluster analysis was used to classify the 35 common species into two species groups, and the 30 sites were classified based on their geographical location. CCA was used to investigate the effects of pollution on foraminiferal assemblages. The results showed that the effects of pollution on foraminiferal assemblages were in the order of heavy metals > TOC > PAHs. Furthermore, the species group I, which consisted of agglutinated taxa including Bigenerina nodosaria, Ammobaculites agglutinans, Textularia spp., T. foliacea, Haplophragmoides canariensis, and several tolerant species of hyaline forms, including Ammonia beccarii, Elphidium advenum, E. hispidulum, Quinqueloculina laevigata, and Q. seminula, was found to be positively influenced by heavy metals. In contrast, species group II, primarily composed of porcelaneous taxa such as Massilina laevigata, Spiroloculina communis, and some hyaline taxa including E. crispum and Elphidium spp., was found to be positively influenced by TOC and PAHs. This work suggest that heavy metal pollution is the main factor influencing foraminiferal assemblages in the study area. The observed positive effect of heavy metals on species group I may indicate the presence of metal-tolerant taxa, whereas the positive effect of TOC and PAHs on species group II suggests that these taxa may be more tolerant of organic pollution. The study highlights the potential of specific foraminiferal assemblages as bioindicators for assessing the impact of different types of pollution on marine ecosystems.

Foraminiferal Biostratigraphy of Well Ad, Western Niger Delta

Micropaleontological analysis of sixty (62) ditch cuttings rock samples collected from interval, 7800 feet to 12,002 feet of well AD, located offshore western Niger Delta was carried out for the investigation of their age and paleodepositional environment. Standard methods and techniques of foraminiferal sample processing and analysis were followed to disaggregate the microfauna from the rock matrix. The studied interval is predominantly made up of 80 to 100 % sandstone, minor shale and siltstone with variable textural properties. Foraminifera study revealed well preserved and diverse species dominated by the calcareous benthic forms. A total of seventy-four (74) foraminiferal species were recovered among which fifty (52) two are calcareous benthic, six (6) are agglutinating forms while sixteen (16) are planktonic foraminifera. On the basis of the faunal assemblage, abundance and diversity of the important foraminiferal events, four (4) foraminiferal zones (Valvulineria spp, Brizalina mandoroveensis, Hanzawaia concentrica and Lenticulina inornata) were recognised and correlated with F300 and F500 to assign an early to middle Miocene age for the sediments. Paleoenvironmental deductions were based primarily on the richness and diversity of foraminiferal species categories. The presence or absence of planktonic foraminifera aided in deciphering open ocean environments. The dominant biofacies associations recorded within the studied section of Well-AD is the Ammonia beccarii biofacies defined by the rare to common occurrences of Ammonia beccarii, Bolivina scalpratamiocenica, Florilus atlanticus and Epistominella vitrea. Brizalina mandoroveensis species, Lenticulina inornata, Hanzawaia strattoni, Eponides eshira, Cribroelphidium galvestonensis and Hanzawaia concentrica were also in association. The Ammonia beccarii biofacies is indicative of the Shallow/Inner Neritic Paleoenvironment, while the Inner Neritic/Middle Neritic Setting is characterized by top occurrence of Valvulineria spp, a rich continuous occurrence of Epistominella vitrea. The paleoenvironment of the studied section of Well-AD is dominantly inner to middle neritic with concomitant minor incursion of outer neritic setting.

Facies Analysis and Paleoenvironmental Reconstruction of Well X, Onshore Niger Delta, Nigeria

Biofacies and lithofacies analysis of one hundred and ninety-two (192) ditch cutting rock samples from well x, onshore Niger Delta was carried out for the purpose of the paleoenvironmental reconstruction of the rock succession. The objectives were to identify the lithofacies units and species of foraminifera and to use both quantitave and qualitative foraminiferal assemblage to recognise the benthonic foraminiferal biofacies and integrate both results for delineation of paleobathymetric and paleoenvironmental settings of sediments penetrated by well x interval studied. The rock samples were prepared through wet-sieve analysis with 63µm mesh sieve size, and subsequently through dry-sieve analysis with 250µm and 500µm mesh sieve sizes. The prepared rock samples were analyzed to generate data for sedimentological grain-size analysis and foraminifera biofacies assemblages. The grain-size analysis provided lithofacies associations, sand/shale ratio and sorting/gradational profile for the studied intervals of well-x while the micropaleontological analysis identified a total of ninety-three (93) well preserved foraminiferal species from which three (3) biofacies associations were delineated. The biofacies include: Ammonia beccarii, Ammonia beccarii/Bolivina scalprata miocenica, and Haplophragmoides compressa/ Valvulina flexilis biofacies indicating Shallow Inner Neritic, Inner- Middle Neritic, and Outer Neritic – Upper Bathyal paleoenvironment respectively. The result of the sand/shale ratio and lithofacies associations indicated penetration into the Agbada Formation of the Niger delta and deposition within shallow to deep marine paleoenvironmental settings, predominantly as channels, intercalated with overbank and distal bar/bay deposits. Synthesis of the biofacies and lithofacies indicated stratigraphic development between coastal deltaic and upper bathyal paleowater depths.

The environmental significance and low-oxygen indicator potential of benthic foraminiferal assemblages in surface sediments off the Changjiang River (Yangtze River) Estuary, China

86 surface sediment samples and a core (CDZS38) from the Changjiang River Estuary (CRE) and its adjacent area were collected to investigate the environmental significance of foraminifera, and determine a microfaunal index for coastal hypoxia to be used for paleoenvironmental studies. Benthic foraminifera and their relationship with environmental parameters including grain size composition and total organic carbon in surface sediment samples were studied. The benthic foraminiferal assemblages were dominated by littoral species in the study area. R-mode cluster analysis identified three clusters based on the percentage of benthic foraminifera. Cluster 1 covers the transitional area between the Radial Sand Ridges of the South Yellow Sea and the CRE. The dominant foraminiferal assemblage is Ammonia beccarii vars.–Ammonia compressiuscula–Quinqueloculina spp., which is a good environmental indicator of an oligotrophic near-shore condition with a strong hydrodynamic force. Cluster 2 covers the inner-shelf off the CRE. The dominant foraminiferal assemblage of Cluster 2 is Epistominella naraensis–Bolivina cochei–Bulimina marginata, which can be used to represent a eutrophic, hypoxic inner-shelf environment. Cluster 3 covers the Hangzhou Bay, which is a typical macro-tidal river mouth. The dominant foraminiferal assemblage of Cluster 3 is A. beccarii vars.–E. naraensis–Ammonia convexidorsa, which is indicative of an environment that is strongly disturbed by tidal currents and influenced by substances from the Changjiang River. The occurrence of E. naraensis, B. marginata and B. cochei is always associated with the hypoxic region. With the correlation analysis with environmental parameters, these species can be considered low-oxygen foraminiferal assemblages (LOFA). We generated a low-oxygen foraminiferal index (the ratio of LOFA to the sum of LOFA and Euryhaline species) to explore the development of hypoxia at the inner-shelf off the CRE, and applied this index to the short core CDZS38. The result indicated that high LOFI values found for CDZS38 is consistent with the recorded trends in hypoxia and harmful algae bloom (HAB) for this area over the past 59 years, and reflect an increase in the hypoxic conditions over this time period.

Spatial Distribution of Benthic Foraminifera in the Neretva Channel (Croatia Coast): Faunal Response to Environmental Parameters

Benthic foraminiferal assemblages have been studied at 11 sediment surface samples located in the Neretva Channel covering the delta habitat and the adjacent open sea areas. The major objective of the investigation was to explore the main environmental parameters affecting the benthic foraminifera compositional changes. To this end, a statistical approach was applied that integrates micropaleontological data with physical, geochemical and sedimentological parameters (total organic carbon and grain size). Statistical analyses identified four distinct groups (cluster A1, A2, B1, B2) corresponding to different environmental settings. Cluster A1 groups samples under Neretva river influence and is characterized by Aubignyna perlucida, Nonionella turgida, Eggerelloides scaber and Rectuvigerina sp.; species able to live in organic-matter-rich sediments and in a wide range of oxygen content. Cluster A2 includes samples distant from the fluvial outlet and samples along the NW coast partially influenced by the Neretva river plume. In these environmental conditions, Ammonia beccarii, Bulimina marginata, Nonionella turgida and Textularia sp. resulted as the most characteristic taxa. Cluster B1 distinguishes the deepest stations which are in connection with the open Adriatic Sea. Here Asterigerinata mamilla, Buccella granulata, Cibicides group, Reussella spinulosa and Textularia sp. reach their maximum abundance associated with coarse-grained sediments. Cluster B2 groups samples collected in the inner bay of the southernmost sector of the studied area characterized by silt and clay and a negligible influence by river inputs. The benthic microfauna is principally composed of Miliolids, Porosononion granosum and Textularia sp.

Distribution and ecology of benthic foraminifera in the Santoña estuary, Spain

The living and dead assemblages in the Santoña estuary were studied seasonally in order to determine the distribution and abundance of the benthic foraminifera in this area. Samples were collected from Winter 1983 to summer 1985 to document the seasonal variation of the faunas and various ecological factors in the intertidal zone. Salinity is thought to be the main control of the living assemblages and two different biofacies characterising the upper and lower areas have been defined. Ammonia beccarii and Haynesina germanica are the most dominant forms throughout the estuary with Miliammina fusca as co-dominant in the upper estuary and Quinqueloculina seminulum as co-dominant in the lower estuary. The dominant living species are also dominant in the dead assemblages but in the latter the agglutinated indigenous component is much more abundant. This compositional difference is thought to be caused by production rates and change in the environmental conditions within the estuary. The living and dead assemblages have been analysed and compared using the Fisher a diversity index, Triangular plot of wall types and Sanders similarity index.

Environmental Evolution and Human Adaption Recorded From a Salt Production Site at the Coastal Plain of Laizhou Bay, China

The southern coast of the Laizhou Bay is considered as one of important areas for the origin and development of sea salt production in Eastern China. Archaeologists have collected rich materials to better understand history of salt production in the region, but how environmental change influences early salt production is still unknown. Here we collected samples at the Shuangwangcheng (SWC) site in the southern plain of Laizhou Bay. We conducted grain size, mollusk and foraminifera analysis to examine the evolution of sedimentary environment and restored the human adaptions to environmental change. The results showed that the sedimentary environment of study area was lower tidal flat during 6400~5900 yr BP as indicated by coarse and well sorted grain size, high abundance of foraminifera, and the Ammonia beccarii vars. - Quinqueloculina akneriana foraminifera assemblage. Sedimentary environment changed from intertidal to supratidal flat with decreasing abundance of foraminifera and finer upward grain size at 5900~ 4300 yr BP. After 4300 yr BP, this area was less affected by seawater, which could be reflected by the appearance of freshwater mollusk and rarely discovered foraminifera. Our retrieved environment changes were closely related with ancient human activities. The Holocene transgression constrained the Dawenkou cultural sites within the inland areas with higher altitude. The exposed coast lowlands after sea retreat were initially not suitable for human survival except sporadic salt production sites of the Longshan culture. These conditions were improved during the Shang and Zhou Dynasties when humans widely used the particular natural resources of underground brine for salt production, and then a large number of salt production sites appeared, which made this region develop into an important origin center of salt production. Our research suggests that salt production was an economic activity that was adopted by people to adapt to the harsh environment, which is of great significance for understanding the evolution of the human-environmental relationship in the coastal area.

Distribution and diversity of Meiobenthos in southern Caspian Sea (Mazandaran-Iran)

Biodiversity and distribution of benthic Meiobenthos in the sediments of the Southern Caspian Sea were studied in order to introduce and determine their relationship with the environmental factors. From 12 stations (ranging in depths from 5, 10, 20 and 50 meters), sediment samples were gathered for four seasons (2012). Temperature, salinity, dissolved Oxygen and pH were measured during sampling with CTD (conductivity, temperature and Depth). Percentage grain size and total organic matter and calcium carbonate were measured. The average water temperature ranged from 9.52 to 23.93 ͦC, dissolved Oxygen from 7.71 to 10.53 mg/L, salinity from 10.57±0.07 to 10.75±0.04 ppt., pH from 7.44±0.29 to 7.41±0.22, EC from 17.97±0.12 to 18.30±0.04 μs/cm2, TDS from 8.92±0.04 to 9.14±0.02 mg/L, total organic matter from 5.83±1.43 to 6.25±0.97% and calcium carbonate fluctuated from 2.36±0.36 to 1.68±0.19%. From the 4 groups of animals (Foraminifera, Crustacea, Worms and Mollusca), 40 species belonging to 29 genera of 25 families were identified Ammonia beccarii caspica, was the common species in all sampling stations. Depth was an important factor in the distribution of meiobenthos. Mean of maximum and minimum Shannon index were measured at depth of 5m and 50 m and were in the order of 0.93 and 0.43, respectively. Account of Shannon and Peilou's index showed that this area is under pressure and is not steady.

Live (stained) benthic foraminifera from the West-Gironde Mud Patch (Bay of Biscay, NE Atlantic): Assessing the reliability of bio-indicators in a complex shelf sedimentary unit.

Live (Rose Bengal stained) shelf foraminiferal faunas have been studied at seven stations located along a shore-open ocean transect between 39 and 69-m depth in the West-Gironde Mud Patch (WGMP) (Bay of Biscay, NE Atlantic) to understand how complex environmental conditions (e.g., organic matter, oxygenation, sedimentary facies) control their ecological patterns (i.e., diversity, faunal composition, standing stock, and microhabitats). To do so, the WGMP was sampled in August 2017, at the end of the succession of phytoplankton blooms occurring in spring and summer. This morpho-sedimentary unit is bathed by well-oxygenated bottom waters and characterized by clay-silt facies containing variably degraded phytodetritus and traces of terrestrial organic matter. Oxygen penetration depth within the sediment is less than 7 ± 3 mm, indicating efficient organic matter in-sediment mineralization by aerobic respiration. Foraminiferal richness (S) presents relatively moderate values ranging between 15 and 35 taxa. According to Shannon Index H’, foraminiferal diversity tends to increase with water depth. Accordingly, the relative contribution of Eggerelloides scaber, the dominant foraminiferal species at all stations, decreases with increased depth and decreased proximity to the coast. The shallowest station (Station 1, 39 m), closest to the shore, is characterised by E. scaber, Quinqueloculina laevigata and Ammonia beccarii, species typical of inner-shelf environments constrained by high-energy hydrodynamics and river discharge. Surficial sediments at Station 1 constitute of winnowed sands depleted in organic carbon. Towards the centre of the WGMP, where clay-silt facies contain variably degraded marine phytodetritus and terrestrial organic compounds, foraminiferal faunas are characterized by Bulimina aculeata, Ammonia falsobeccarrii, Nouria polymorphinoides and Nonionoides turgidus. Yet E. scaber remains the most dominant taxon. Deeper stations (>55 m depth) located at the distal part of the mud patch are dominated by B. aculeata, A. falsobeccarrii, N. polymorphinoides and E. scaber. Accompanying these taxa are Bulimina marginata, Rectuvigerina phlegeri, Nonion faba and Paracassidulina neocarinata, which are typical of mid- and outer-shelf ecosystems enriched in sedimentary organic matter.

Reconstruction of the paleoenvironment of the late Quaternary sediments of the Kerala coast, SW India

• Sediments of the Kerala coast are deposited under terrigenous to littoral with diverse energy regime. • Depositional landforms ; estuary , lagoon , and paleo-strandline are carved by sea-level changes. • Stronger monsoon in the early Holocene and a weaker in the Last Glacial Maximum was observed. • Along the Kerala coast, the paleo-shoreline is 9.5 km landward from the present-day shoreline . • A conceptual sediment depositional model is proposed for the evolution of the Kerala coast. Recurrent sea-level changes are reflected in the formation of coastal landforms; estuary, lakes, lagoons and barrier beaches during the late Quaternary period along the Kerala coast, SW India. The sediment core from these landforms was addressed for sediment lithofacies, geochemical parameters and associated foraminiferal assemblages to reconstruct the late Quaternary environment. The textural characteristics of the sediment indicate a shallow marine to lagoon and swampy/marsh environment. A layer of coarse sandy sediment (7–9 m thickness) is overlying the late Pleistocene (40 Kyrs BP) sediment sequence. The sediment was deposited under violent to the calm environment attributing its deposition in diverse energy regimes. This is also corroborated with the micro-textures of quartz grains. The geochemical elemental relationship (Rb vs K 2 O, Ni vs TiO 2 , K 2 O/Na 2 O vs SiO 2 /Al 2 O 3 , discriminant function) is established with paleoweathering, provenance and tectonic setting. An abundant population of Ammonia beccarii, A. tepida, E. discoidale, N. scaphum. A. beccarii in the sediments reveals their high tolerance and adaptability to the changing environment. The multiproxy studies on sediments, support a stronger monsoon in the early Holocene leading to the incursion of high-water levels, increased flow discharge and bottom scouring but, weak monsoon and arid climate prevailed during the Last Glacial Maximum (LGM). A conceptual model is proposed to depict the shoreline evolution and its climate.

High precipitation rates characterize biomineralization in the benthic foraminifer Ammonia beccarii

The chemical composition of foraminiferal calcite reflects seawater variables and is therefore a popular paleoceanographic tool. The sedimentary record of foraminiferal shell chemistry is, however, mostly interpreted using empirical calibrations. Since geochemical patterns in foraminifera often deviate from inorganic analogues, there is an ongoing need for a more mechanistic understanding of foraminiferal biomineralization. One of the most elusive, but potentially important parameters characterizing foraminiferal biomineralization is the rate of calcite precipitation. Using a combination of labelling experiments and sub-micrometer imaging of the incorporated label with NanoSIMS, we show that the benthic foraminifer Ammonia beccarii precipitates its calcite at a rate of ∼24 ± 4 nmol/cm2/min. These values are close to maximum reported rates for inorganic calcite precipitation from Mg-depleted seawater, which is consistent with the strong fractionation against Mg during biomineralization. At the same time, the measured precipitation rate is in accordance with the similarity between the foraminiferal Sr/Ca values and ratios from calcite precipitated inorganically at these rates. Our results also show that the observed precipitation rate is surprisingly uniform among specimens and within chamber walls, indicating that the small-scale element banding is not reflecting variability in precipitation rate. Based on our results, we present a conceptual model where foraminiferal calcification is characterized by two major processes: first, active ion transport determines the composition of the calcifying fluid, whereas thermodynamics and process kinetics dictate fractionation and partitioning during the subsequent calcium carbonate precipitation. This model also accounts for a role of seawater transport, which may be important in the first steps of calcification to explain geochemical signatures of other foraminiferal taxa.

Biometry and taxonomy of Adriatic <i>Ammonia</i> species from Bellaria–Igea Marina (Italy)

Abstract. Living Ammonia species and an inventory of dead assemblages from Adriatic subtidal, nearshore environments were investigated at four stations off Bellaria, Italy. Ammonia falsobeccarii, Ammonia parkinsoniana, Ammonia tepida, and Ammonia veneta were recognized in the living (rose-bengal-stained) fauna, and Ammonia bellaria n. sp. is described herein for the first time. Ammonia beccarii was only found in the dead assemblage. The biometry of 368 living individuals was analysed by using light microscopic and scanning electron microscopic images of three aspects. A total of 15 numerical and 8 qualitative parameters were measured and assessed, 5 of which were recognized to be prone to a certain subjectivity of the observer. The accuracy of numerical data as revealed by the mean residuals of parallel measurements by different observers ranged from 0.5 % to 5.5 %. The results indicated a high degree of intraspecific variability. The test sizes of the individual species were log-normally distributed and varied among the stations. Parameters not related to the growth of the individuals, i.e. flatness of the tests, dimensions of the second-youngest chamber, proloculus, umbilical and pore diameter, sinistral–dextral coiling, and umbilical boss size, were recognized as being species-distinctive in combination. They may well supplement qualitative criteria that were commonly used for species discrimination such as a lobate outline, a subacute or rounded peripheral margin, or the degree of ornamentation on the spiral and umbilical sides. The averages of the measured parameters were often lower than the range of previously published values, mainly because the latter were retrieved from a few adult specimens and not from the whole assemblage as in the present approach. We conclude that the unprecedented high proportions of Ammonia beccarii in the northern Adriatic may well be artificial. A robust species identification without genetic analyses is possible by considering designated biometric parameters. This approach is also applicable to earlier literature data, and their re-assessment is critical for a correct denomination of recent genotypes.

Influence of Bottom Water Parameters on the Distribution of Benthic Foraminifera from the Gulf of Mannar, Off Tiruchendur, Southeast Coast of India

Foraminifera are found in all marine environments, but they are very particular about the congenial environment for their reproduction, diversity and abundance. To understand the influence of bottom water parameters on the distribution of foraminifera from the shallow shelf region of Bay of Bengal, off Tiruchendur, Southeast Coast of Tamil Nadu, sediment and bottom water samples were collected at 27 stations, along three traverses viz. from off Veerapandianpattinam, off Tiruchendur and from off Alandurai, ranging in depths from 1.6m to 18.5m. The samples were collected during three seasons representing, summer (May 2016), pre monsoon (October 2016) and winter (January 2017) and thus the total samples amounted to 81. A total of 105 species of foraminifera have been identified from 47 genera, 32 families, 16 superfamilies and 4suborders. Among these 105 foraminiferal species, five were found to be widespread and abundant viz. Ammonia beccarii, A. tepida, Asterorotalia inflata, Nonioniodes boueanum and Quinqueloculina seminulam. Various bottom water parameters such as temperature, salinity, dissolved oxygen and pH were determined and correlated with the foraminiferal population. Temporally, higher temperature, salinity, dissolved oxygen and pH of bottom water observed during summer (May 2016) were congenial for higher population in the study area. Optimum conditions for the higher population and abundance of foraminifera are: Temperature: > 32.0°C, Dissolved oxygen: >6.0 mg/l, Salinity: >32 ppt and pH>8.1.