Review: the effects of secular variation in seawater Mg/Ca on marine biocalcification

Abstract. Synchronized transitions in the polymorph mineralogy of the major reef-building and sediment-producing calcareous marine organisms and abiotic CaCO3 precipitates (ooids, marine cements) throughout Phanerozoic time are believed to have been caused by tectonically induced variations in the Mg/Ca ratio of seawater (molar Mg/Ca>2="aragonite seas", <2="calcite seas"). Here, I assess the geological evidence in support of secular variation in seawater Mg/Ca and its effects on marine calcifiers, and review a series of recent experiments that investigate the effects of seawater Mg/Ca (1.0–5.2) on extant representatives of calcifying taxa that have experienced variations in this ionic ratio of seawater throughout the geologic past. Secular variation in seawater Mg/Ca is supported by synchronized secular variations in (1) the ionic composition of fluid inclusions in primary marine halite, (2) the mineralogies of late stage marine evaporites, abiogenic carbonates, and reef- and sediment-forming marine calcifiers, (3) the Mg/Ca ratios of fossil echinoderms, molluscs, rugose corals, and abiogenic carbonates, (4) global rates of tectonism that drive the exchange of Mg2+ and Ca2+ along zones of ocean crust production, and (5) additional proxies of seawater Mg/Ca including Sr/Mg ratios of abiogenic carbonates, Sr/Ca ratios of biogenic carbonates, and Br concentrations in marine halite. Laboratory experiments have revealed that aragonite-secreting bryopsidalean algae and scleractinian corals and calcite-secreting coccolithophores exhibit higher rates of calcification and growth in experimental seawaters formulated with seawater Mg/Ca ratios that favor their skeletal mineral. These results support the assertion that seawater Mg/Ca played an important role in determining which hypercalcifying marine organisms were the major reef-builders and sediment-producers throughout Earth history. The observation that primary production increased along with calcification within the bryopsidalean and coccolithophorid algae in mineralogically favorable seawater is consistent with the hypothesis that calcification promotes photosynthesis within some species of these algae through the liberation of CO2. The experiments also revealed that aragonite-secreting bryopsidalean algae and scleractinian corals, and bacterial biofilms that secrete a mixture of aragonite and high Mg calcite, began secreting an increased proportion of their calcium carbonate as the calcite polymorph in the lower-Mg/Ca experimental seawaters. Furthermore, the Mg/Ca ratio of calcite secreted by the coccolithophores, coralline red algae, reef-dwelling animals (crustacea, urchins, calcareous tube worms), bacterial biofilms, scleractinian corals, and bryopsidalean algae declined with reductions in seawater Mg/Ca. Notably, Mg fractionation in autotrophic organisms was more strongly influenced by changes in seawater Mg/Ca than in heterotrophic organisms, a probable consequence of autotrophic organisms inducing a less controlled mode of calcification simply through the removal of CO2 via photosynthesis. These results indicate that biomineralogical control can be partially overridden by ambient seawater Mg/Ca and suggest that modern aragonite-secreting organisms may have secreted a mixture of aragonite and low Mg calcite, and that modern high Mg calcite-secreting organisms probably secreted low Mg calcite, in calcite seas of the past. These effects of seawater Mg/Ca on the polymorph mineralogy and calcite Mg/Ca ratio of calcareous skeletons should be accounted for in thermal-chemical reconstructions of seawater that are based upon skeletal Mg/Ca. Lastly, by identifying how marine calcifiers respond to changes in seawater Mg/Ca and absolute Ca2+ concentration, this work should enhance our interpretation of parallel studies investigating the effects of anthropogenic CO2-induced ocean acidification on marine calcification.

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A Scientific Search for Altruism

10.1093/oso/9780190651374.001.0001 ◽

2018 ◽

Author(s):

C. Daniel Batson

Keyword(s):

Human Nature ◽

Scientific Method ◽

Laboratory Experiments ◽

Fundamental Question ◽

Empathic Concern ◽

Altruistic Motivation ◽

The Past ◽

Past Half Century ◽

Series Of Experiments ◽

Past Half

This book provides an example of how the scientific method can be used to address a fundamental question about human nature. For centuries—indeed for millennia—the egoism–altruism debate has echoed through Western thought. Egoism says that the motivation for everything we do, including all of our seemingly selfless acts of care for others, is to gain one or another self-benefit. Altruism, while not denying the force of self-benefit, says that under certain circumstances we can care for others for their sakes, not our own. Over the past half-century, social psychologists have turned to laboratory experiments to provide a scientific resolution of this human nature debate. The experiments focused on the possibility that empathic concern—other-oriented emotion elicited by and congruent with the perceived welfare of someone in need—produces altruistic motivation to remove that need. With carefully constructed experimental designs, these psychologists have tested the nature of the motivation produced by empathic concern, determining whether it is egoistic or altruistic. This series of experiments has provided an answer to a fundamental question about what makes us tick. Framed as a detective story, the book traces this scientific search for altruism through the numerous twists and turns that led to the conclusion that empathy-induced altruism is indeed part of our nature. It then examines the implications of this conclusion—negative implications as well as positive—both for our understanding of who we are as humans and for how we might create a more humane society.

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Sphingolipids of Asteroidea and Holothuroidea: Structures and Biological Activities

Marine Drugs ◽

10.3390/md19060330 ◽

2021 ◽

Vol 19 (6) ◽

pp. 330

Author(s):

Timofey V. Malyarenko ◽

Alla A. Kicha ◽

Valentin A. Stonik ◽

Natalia V. Ivanchina

Keyword(s):

Marine Invertebrates ◽

Biological Activities ◽

Complete Information ◽

Structural Features ◽

Marine Organisms ◽

Structural Components ◽

Chemical Structures ◽

The Past ◽

Complex Lipids ◽

Complex Sphingolipids

Sphingolipids are complex lipids widespread in nature as structural components of biomembranes. Commonly, the sphingolipids of marine organisms differ from those of terrestrial animals and plants. The gangliosides are the most complex sphingolipids characteristic of vertebrates that have been found in only the Echinodermata (echinoderms) phylum of invertebrates. Sphingolipids of the representatives of the Asteroidea and Holothuroidea classes are the most studied among all echinoderms. In this review, we have summarized the data on sphingolipids of these two classes of marine invertebrates over the past two decades. Recently established structures, properties, and peculiarities of biogenesis of ceramides, cerebrosides, and gangliosides from starfishes and holothurians are discussed. The purpose of this review is to provide the most complete information on the chemical structures, structural features, and biological activities of sphingolipids of the Asteroidea and Holothuroidea classes.

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Crashworthiness of Safe Fuels

ASME 1972 International Gas Turbine and Fluids Engineering Conference and Products Show ◽

10.1115/72-gt-27 ◽

1972 ◽

Author(s):

R. A. Rockow ◽

L. M. Shaw

Keyword(s):

Performance Evaluation ◽

Fire Hazard ◽

Full Scale ◽

Safety Performance ◽

Screening Tests ◽

Aircraft Accidents ◽

The Past ◽

Relative Safety ◽

Series Of Experiments ◽

Aircraft Crash

Safety fuels such as emulsified and gelled fuels have been studied over the past several years as one means for reducing the post-crash fire hazard associated with aircraft accidents. However, through the work described herein, only recently has a quantitative evaluation been made to characterize the safety performance of these fuels. The safety performance evaluation program described in this paper includes an initial series of screening tests designed to obtain the characteristics of safe fuels in the aircraft crash environment. The authenticity of the screening tests relative to the full-scale crash environment was evaluated through a second series of experiments designed to simulate a full-scale aircraft crash environment. A crashworthiness evaluation criterion was established in terms of an “ignition susceptibility parameter” to quantitize the relative safety performance of different fuels. The conclusions of this research clearly show that significant savings in lives and equipment can be realized if safe fuels which perform within the non-hazardous envelope of the ignition susceptibility parameter are operationally incorporated in present-day aircraft.

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An Enquiry into the Process of Categorization of Pictures and Words

Perceptual and Motor Skills ◽

10.2466/pms.2003.96.1.267 ◽

2003 ◽

Vol 96 (1) ◽

pp. 267-287 ◽

Cited By ~ 4

Author(s):

Madhubalan Viswanathan ◽

Terry L. Childers

Keyword(s):

Semantic Processing ◽

Semantic Relatedness ◽

Experimental Paradigm ◽

The Past ◽

Word Categorization ◽

Multiple Routes ◽

Methodological Problems ◽

Series Of Experiments ◽

Pictures And Words ◽

Salient Features

This paper reports a series of experiments conducted to study the categorization of pictures and words. Whereas some studies reported in the past have found a picture advantage in categorization, other studies have yielded no differences between pictures and words This paper used an experimental paradigm designed to overcome some methodological problems to examine picture-word categorization. The results of one experiment were consistent with an advantage for pictures in categorization. To identify the source of the picture advantage in categorization, two more experiments were conducted. Findings suggest that semantic relatedness may play an important role in the categorization of both pictures and words. We explain these findings by suggesting that pictures simultaneously access both their concept and visually salient features whereas words may initially access their concept and may subsequently activate features. Therefore, pictures have an advantage in categorization by offering multiple routes to semantic processing.

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New Italian directional and intensity archaeomagnetic reference curves for the past 3000 years: Insights on secular variation and implications on dating

Archaeometry ◽

10.1111/arcm.12603 ◽

2020 ◽

Author(s):

E. Tema ◽

P. Lanos

Keyword(s):

Secular Variation ◽

The Past ◽

Reference Curves

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Implications of Dipole Moment Secular Variation from 50,000–10,000 Years for the Radiocarbon Record

Radiocarbon ◽

10.1017/s0033822200013618 ◽

1992 ◽

Vol 34 (2) ◽

pp. 189-198 ◽

Cited By ~ 4

Author(s):

R. S. Sternberg ◽

P. E. Damon

Keyword(s):

Dipole Moment ◽

Production Function ◽

Secular Variation ◽

Good Match ◽

Average Value ◽

The Past ◽

Dc Gain ◽

Ramp Function ◽

Holocene Record ◽

Linear Ramp

Sparse paleointensity data from 10–50 ka suggest that the average dipole moment (DM) was 50–75% of the average of 8.67 μ 1022 A m2 for the past 5 Ma, and 8.75 μ 1022 for the past 12 ka. A linear ramp function, increasing the DM from 4 to 8.75 μ 1022 A m2 between 50–10 ka BP, generates a total 14C inventory of 126 dpm/cme2, agreeing very well with an inventory assay of 128 dpm/cme2, which includes 14C in sediments. With the Lingenfelter and Ramaty (1970) production function and a model DC gain of about 100, this DM function would give a Δ14C of 500‰ at 20 ka BP, consistent with the Barbados coral record, and also gives a good match to the Holocene record. A Laschamp geomagnetic event at about 45 ka BP, with a DM of 25% of its average value and lasting 5 ka, would only increase the present inventory by 0.3–1.2 dpm/cme2, and would probably have only a small effect on Δ14C at 20 ka BP, but could produce a short-lived 14C spike of over 500‰.

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STUDIES ON REPELLENTS FOR BITING FLIES

The Canadian Entomologist ◽

10.4039/ent7138-2 ◽

1939 ◽

Vol 71 (2) ◽

pp. 38-44 ◽

Cited By ~ 9

Author(s):

C. G. MacNay

Keyword(s):

The Past ◽

Series Of Experiments ◽

The Many

In view of the known lack of effectiveness and doubtful value of many of the materials cited in literature as being of value as repellents for biting flies, a series of experiments was carried out at the direction of the Dominion Entomologist, during the past three seasons, with the object of determining which of the many materials recommended as repellents might be the most effective and which the most lasting in effect.

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A comparison of geomagnetic secular variation as recorded by historical, archaeomagnetic and palaeomagnetic measurements

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1982.0070 ◽

1982 ◽

Vol 306 (1492) ◽

pp. 103-112 ◽

Cited By ~ 15

Keyword(s):

Magnetic Field ◽

Lake Sediments ◽

Secular Variation ◽

Geomagnetic Field ◽

Secular Change ◽

Mathematical Approach ◽

Geomagnetic Secular Variation ◽

The Past ◽

Palaeomagnetic Data ◽

Field Behaviour

Palaeomagnetic methods can extend the documentary record of changes in the Earth’s magnetic field far into the past. Tolerable agreement is found between various methods, demonstrating the geophysical value of palaeomagnetic experiments. Combining results from the different approaches of investigating secular change can lead to a better perspective and to superior models of geomagnetic field behaviour. Lake sediments have recently been found to hold remarkably detailed signatures of past field changes. A mathematical approach to formulating an empirical description of global geomagnetic field behaviour is proposed and applied to palaeomagnetic data spanning the last 10 ka.

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Interactions Between Microorganisms and Marine Microplastics: A Call for Research

Marine Technology Society Journal ◽

10.4031/mtsj.45.2.2 ◽

2011 ◽

Vol 45 (2) ◽

pp. 12-20 ◽

Cited By ~ 91

Author(s):

Jesse P. Harrison ◽

Melanie Sapp ◽

Michaela Schratzberger ◽

A. Mark Osborn

Keyword(s):

Adverse Effects ◽

Food Webs ◽

Ecological Integrity ◽

Emerging Pollutants ◽

Marine Organisms ◽

Coastal Sediments ◽

Toxic Chemicals ◽

Global Functioning ◽

Microbial Biofilms ◽

Marine Biosphere

AbstractSynthetic thermoplastics constitute the majority by percentage of anthropogenic debris entering the Earth’s oceans. Microplastics (≤5-mm fragments) are rapidly emerging pollutants in marine ecosystems that may transport potentially toxic chemicals into macrobial food webs. This commentary evaluates our knowledge concerning the interactions between marine organisms and microplastics and identifies the lack of microbial research into microplastic contamination as a significant knowledge gap. Microorganisms (bacteria, archaea, and picoeukaryotes) in coastal sediments represent a key category of life with reference to understanding and mitigating the potential adverse effects of microplastics due to their role as drivers of the global functioning of the marine biosphere and as putative mediators of the biodegradation of plastic-associated additives, contaminants, or even the plastics themselves. As such, research into the formation, structure, and activities of microplastic-associated microbial biofilms is essential in order to underpin management decisions aimed at safeguarding the ecological integrity of our seas and oceans.

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