Palaeoceanographic implications of abundance and mean proloculus diameter of benthic foraminiferal speciesEpistominella exigua in sub-surface sediments from distal Bay of Bengal fan

Saraswat, Rajeev; Nigam, R.; Barreto, Lea

doi:10.1007/bf02702022

Cited by 22 publications

(5 citation statements)

References 23 publications

(33 reference statements)

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“…a large proloculus at organic pollution (i.e. high food supply) [ 73 ], optimal growth and high food availability [ 74 ], and temperature and salinity [ 75 , 76 ]. As such, an extensive study of the plasticity of proloculus sizes in modern foraminifers would be timely.…”

Section: Discussionmentioning

confidence: 99%

Strategies in times of crisis—insights into the benthic foraminiferal record of the Palaeocene–Eocene Thermal Maximum

Schmidt

Thomas

Authier

et al. 2018

Phil. Trans. R. Soc. A.

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Climate change is predicted to alter temperature, carbonate chemistry and oxygen availability in the oceans, which will affect individuals, populations and ecosystems. We use the fossil record of benthic foraminifers to assess developmental impacts in response to environmental changes during the Palaeocene–Eocene Thermal Maximum (PETM). Using an unprecedented number of µ-computed tomography scans, we determine the size of the proloculus (first chamber), the number of chambers and the final size of two benthic foraminiferal species which survived the extinction at sites 690 (Atlantic sector, Southern Ocean, palaeodepth 1900 m), 1210 (central equatorial Pacific, palaeodepth 2100 m) and 1135 (Indian Ocean sector, Southern Ocean, palaeodepth 600–1000 m). The population at the shallowest site, 1135, does not show a clear response to the PETM, whereas those at the other sites record reductions in diameter or proloculus size. Temperature was similar at all sites, thus it is not likely to be the reason for differences between sites. At site 1210, small size coincided with higher chamber numbers during the peak event, and may have been caused by a combination of low carbonate ion concentrations and low food supply. Dwarfing at site 690 occurred at lower chamber numbers, and may have been caused by decreasing carbonate saturation at sufficient food levels to reproduce. Proloculus size varied strongly between sites and through time, suggesting a large influence of environment on both microspheric and megalospheric forms without clear bimodality. The effect of the environmental changes during the PETM was more pronounced at deeper sites, possibly implicating carbonate saturation.This article is part of a discussion meeting issue ‘Hyperthermals: rapid and extreme global warming in our geological past’.

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Section: Discussionmentioning

confidence: 99%

Strategies in times of crisis—insights into the benthic foraminiferal record of the Palaeocene–Eocene Thermal Maximum

Schmidt

Thomas

Authier

et al. 2018

Phil. Trans. R. Soc. A.

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“…The previous work on foraminiferal distribution along the beaches and the estuaries adjoining the Bay of Bengal was initiated by Ghosh (1966) and followed by various researchers (Bhalla 1968;Ghosh and Bhattacharjee 1993; see Khare et al 2007 for a comprehensive review). Foraminifera from the Bay of Bengal have also been used to reconstruct paleomonsoon (Cullen and Duplessy 1979;Cullen 1981;Duplessy 1982;Saraswat et al 2005;Rana and Nigam 2009;Panchang and Nigam 2012). Even though, extensive studies to document benthic foraminiferal distribution have been carried out along the east coast of India, no detailed study has yet been carried out to document recent benthic foraminiferal distribution and their ecological preferences from continental shelf region off Ganga-Brahmaputra-Mahanadi region.…”

Section: Introductionmentioning

confidence: 99%

Assessing the suitability of benthic foraminiferal morpho-groups to reconstruct paleomonsoon from Bay of Bengal

2016

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Temporal changes in benthic foraminiferal morpho-groups were suggested as an effective proxy to reconstruct past monsoon intensity from the Arabian Sea. Here, in order to test the applicability of temporal variation in morpho-groups to reconstruct past monsoon intensity from the Bay of Bengal, we have documented recent benthic foraminiferal distribution from the continental shelf region of the northwestern Bay of Bengal. Based on the external morphology, benthic foraminifera were categorized into rounded symmetrical (RSBF) and angular asymmetrical benthic foraminifera (AABF). Additionally, a few other dominant groups were also identified based on test composition (agglutinated, calcareous) and abundance (Asterorotalids and Nonions). The relative abundance of each group was compared with the ambient physico-chemical conditions, including dissolved oxygen, organic matter, salinity and temperature. We report that the RSBF are abundant in comparatively warm and well oxygenated waters of low salinity, suggesting a preference for high energy environment, whereas AABF dominate relatively cold, hypersaline deeper waters with low dissolved oxygen, indicating a low energy environment. The agglutinated foraminifera, Asterorotalids and Nonions dominate shallow water, low salinity regions, whereas the calcareous benthic foraminiferal abundance increases away from the riverine influx regions. Food availability, as estimated from organic carbon abundance in sediments, has comparatively less influence on faunal distribution in the northwestern Bay of Bengal, as compared to dissolved oxygen, temperature and salinity. We conclude that the factors associated with freshwater influx affect the distribution of benthic foraminiferal morpho-groups in the northwestern Bay of Bengal and thus it can be used to reconstruct past monsoon intensity from the Bay of Bengal.

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“…However, previous studies have proposed a paleoclimate proxy based on proloculus sizes, suggesting that mean proloculus size decreases with warming seawater temperature and increasing salinity (Nigam 1986; Nigam and Rao 1987; Nigam and Khare 1995; Saraswat et al 2005). These studies calculated the mean proloculus size of a population using both microspheric and megalospheric forms; thus, a decrease in mean proloculus size reflects a greater proportion of microspheric forms.…”

Section: Discussionmentioning

confidence: 99%

“…Studies of within-species biogeographic variation in proloculus sizes of megalospheric forms also suggest that the environment underlies proloculus size distributions (Myers 1943; Eder et al 2016), but the environmental variable(s) shaping these patterns has not been identified nor have these patterns been quantified (see Beavington-Penney and Racey 2004). Furthermore, others have proposed that previously documented patterns of within-species proloculus size change might reflect the mixing of megalospheric and microspheric individuals (Röttger et al 1980; Racey 2001; Beavington-Penney and Racey 2004), because it can be difficult to differentiate between the two forms (e.g., Nigam and Khare 1995; Saraswat et al 2005). Herein, our results suggest that among-species patterns of megalospheric proloculus sizes are not constrained by the local environment, and consequently, ancient environmental conditions cannot be inferred from the study of fossil foraminiferal proloculus sizes alone.…”

Section: Discussionmentioning

confidence: 99%

Environmental influence on growth history in marine benthic foraminifera

Keating-Bitonti

Payne

2018

Paleobiology

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Energy availability influences natural selection on the ontogenetic histories of organisms. However, it remains unclear whether physiological controls on size remain constant throughout ontogeny or instead shift as organisms grow larger. Benthic foraminifera provide an opportunity to quantify and interpret the physicochemical controls on both initial (proloculus) and adult volumes across broad environmental gradients using first principles of cell physiology. Here, we measured proloculus and adult test dimensions of 129 modern rotaliid species from published images of holotype specimens, using holotype size to represent the maximum size of all species’ occurrences across the North American continental margin. We merged size data with mean annual temperature, dissolved oxygen concentration, particulate organic carbon flux, and seawater calcite saturation for 718 unique localities to quantify the relationship between physicochemical variables and among-species adult/proloculus size ratios. We find that correlation of community mean adult/proloculus size ratios with environmental parameters reflects covariation of adult test volume with environmental conditions. Among-species proloculus sizes do not covary identifiably with environmental conditions, consistent with the expectation that environmental constraints on organism size impose stronger selective pressures on adult forms due to lower surface area-to-volume ratios at larger sizes. Among-species adult/proloculus size ratios of foraminifera occurring in resource-limited environments are constrained by the limiting resource in addition to temperature. Identified limiting resources are food in oligotrophic waters and oxygen in oxygen minimum zones. Because among-species variations in adult/proloculus size ratios from the North American continental margin are primarily driven by the local environment’s influence on adult sizes, the evolution of foraminiferal sizes over the Phanerozoic may have been strongly influenced by changing oceanographic conditions. Furthermore, lack of correspondence between among-species proloculus sizes and environmental conditions suggests that offspring sizes in foraminifera are rarely limited by physiological constraints and are more susceptible to selection related to other aspects of fitness.

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Palaeoceanographic implications of abundance and mean proloculus diameter of benthic foraminiferal speciesEpistominella exigua in sub-surface sediments from distal Bay of Bengal fan

Cited by 22 publications

References 23 publications

Strategies in times of crisis—insights into the benthic foraminiferal record of the Palaeocene–Eocene Thermal Maximum

Strategies in times of crisis—insights into the benthic foraminiferal record of the Palaeocene–Eocene Thermal Maximum

Assessing the suitability of benthic foraminiferal morpho-groups to reconstruct paleomonsoon from Bay of Bengal

Environmental influence on growth history in marine benthic foraminifera

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