A report on Ocean acidification

Estimated change in seawater pH caused by human-created carbon dioxide between the 1700s and the 1990s, from the Global Ocean Data Analysis Project (GLODAP) and the World Ocean Atlas
Here is a detailed image of the full carbon cycle
NOAA provides evidence for the upwelling of "acidified" water onto the Continental Shelf. In the figure above, note the vertical sections of (A) temperature, (B) aragonite saturation, (C) pH, (D) DIC, and (E) p on transect line 5 off Pt. St. George, California. The potential density surfaces are superimposed on the temperature section. The 26.2 potential density surface delineates the location of the first instance in which the undersaturated water is upwelled from depths of 150 to 200 m onto the shelf and outcropping at the surface near the coast. The red dots represent sample locations.
Ocean Acidification Infographic
The cycle between the atmosphere and the ocean
Distribution of (A) aragonite and (B) calcite saturation depth in the global oceans
This map shows changes in the aragonite saturation level of ocean surface waters between the 1880s and the most recent decade (2006–2015). Aragonite is a form of calcium carbonate that many marine animals use to build their skeletons and shells. The lower the saturation level, the more difficult it is for organisms to build and maintain their skeletons and shells. A negative change represents a decrease in saturation.
Here is detailed diagram of the carbon cycle within the ocean
Bjerrum plot: Change in carbonate system of seawater from ocean acidification.
Shells of pteropods dissolve in increasingly acidic conditions caused by increased amounts of atmospheric
A normally-protective shell made thin, fragile and transparent by acidification
Drivers of hypoxia and ocean acidification intensification in upwelling shelf systems. Equatorward winds drive the upwelling of low dissolved oxygen (DO), high nutrient, and high dissolved inorganic carbon (DIC) water from above the oxygen minimum zone. Cross-shelf gradients in productivity and bottom water residence times drive the strength of DO (DIC) decrease (increase) as water transits across a productive continental shelf.
Demonstrator calling for action against ocean acidification at the People's Climate March (2017).
Ocean acidification: mean seawater pH. Mean seawater pH is shown based on in-situ measurements of pH from the Aloha station.
"Present day" (1990s) sea surface pH
Present day alkalinity
"Present day" (1990s) sea surface anthropogenic {{chem|CO|2}}
Vertical inventory of "present day" (1990s) anthropogenic {{chem|CO|2}}
Change in surface {{chem|CO|3|2-}} ion from the 1700s to the 1990s
Present day DIC
Pre-Industrial DIC
A NOAA (AOML) in situ {{chem|CO|2}} concentration sensor (SAMI-CO2), attached to a Coral Reef Early Warning System station, utilized in conducting ocean acidification studies near coral reef areas
A NOAA (PMEL) moored autonomous {{chem|CO|2}} buoy used for measuring {{chem|CO|2}} concentration and ocean acidification studies

Ongoing decrease in the pH value of the Earth's oceans, caused by the uptake of carbon dioxide from the atmosphere.

- Ocean acidification
Estimated change in seawater pH caused by human-created carbon dioxide between the 1700s and the 1990s, from the Global Ocean Data Analysis Project (GLODAP) and the World Ocean Atlas

42 related topics with Alpha

Overall

Crystal structure of dry ice

Carbon dioxide

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Chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms.

Chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms.

Crystal structure of dry ice
Stretching and bending oscillations of the CO2 carbon dioxide molecule. Upper left: symmetric stretching. Upper right: antisymmetric stretching. Lower line: degenerate pair of bending modes.
Pellets of "dry ice", a common form of solid carbon dioxide
Pressure–temperature phase diagram of carbon dioxide. Note that it is a log-lin chart.
Carbon dioxide bubbles in a soft drink
Dry ice used to preserve grapes after harvest
Use of a CO2 fire extinguisher
Comparison of the pressure–temperature phase diagrams of carbon dioxide (red) and water (blue) as a log-lin chart with phase transitions points at 1 atmosphere
A carbon-dioxide laser
Keeling curve of the atmospheric CO2 concentration
Atmospheric CO2 annual growth rose 300% since the 1960s.
Annual flows from anthropogenic sources (left) into Earth's atmosphere, land, and ocean sinks (right) since the 1960s. Units in equivalent gigatonnes carbon per year.
Pterapod shell dissolved in seawater adjusted to an ocean chemistry projected for the year 2100.
Overview of the Calvin cycle and carbon fixation
Overview of photosynthesis and respiration. Carbon dioxide (at right), together with water, form oxygen and organic compounds (at left) by photosynthesis, which can be respired  to water and (CO2).
Symptoms of carbon dioxide toxicity, by increasing volume percent in air.
Rising levels of CO2 threatened the Apollo 13 astronauts who had to adapt cartridges from the command module to supply the carbon dioxide scrubber in the Lunar Module, which they used as a lifeboat.
CO2 concentration meter using a nondispersive infrared sensor

When carbon dioxide dissolves in water it forms carbonic acid (H2CO3), which causes ocean acidification as atmospheric CO2 levels increase.

Fast carbon cycle showing the movement of carbon between land, atmosphere, and oceans in billions of tons (gigatons) per year. Yellow numbers are natural fluxes, red are human contributions, white are stored carbon. The effects of the slow carbon cycle, such as volcanic and tectonic activity are not included.

Carbon cycle

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Biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.

Biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.

Fast carbon cycle showing the movement of carbon between land, atmosphere, and oceans in billions of tons (gigatons) per year. Yellow numbers are natural fluxes, red are human contributions, white are stored carbon. The effects of the slow carbon cycle, such as volcanic and tectonic activity are not included.
Detail of anthropogenic carbon flows, showing cumulative mass in gigatons during years 1850-2018 (left) and the annual mass average during 2009-2018 (right).
CO2 concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black)
Amount of carbon stored in Earth's various terrestrial ecosystems, in gigatonnes.
A portable soil respiration system measuring soil CO2 flux.
Diagram showing relative sizes (in gigatonnes) of the main storage pools of carbon on Earth. Cumulative changes (thru year 2014) from land use and emissions of fossil carbon are included for comparison.
Carbon is tetrahedrally bonded to oxygen
Knowledge about carbon in the core can be gained by analysing shear wave velocities
Schematic representation of the overall perturbation of the global carbon cycle caused by anthropogenic activities, averaged from 2010 to 2019.
The pathway by which plastics enter the world's oceans.
Carbon stored on land in vegetation and soils is aggregated into a single stock ct. Ocean mixed layer carbon, cm, is the only explicitly modelled ocean stock of carbon; though to estimate carbon cycle feedbacks the total ocean carbon is also calculated.
Epiphytes on electric wires. This kind of plant takes both CO{{sub|2}} and water from the atmosphere for living and growing.
CO{{sub|2}} in Earth's atmosphere if half of global-warming emissions are not absorbed.<ref name="NASA-20151112-ab" /><ref name="NASA-20151112b" /><ref name="NYT-20151110" /><ref name="AP-20151109" /> (NASA computer simulation).

The increased carbon dioxide has also increased the acidity of the ocean surface by about 30% due to dissolved carbon dioxide, carbonic acid and other compounds, and is fundamentally altering marine chemistry.

Average surface air temperatures from 2011 to 2021 compared to the 1956–1976 average

Climate change

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Contemporary climate change includes both global warming and its impacts on Earth's weather patterns.

Contemporary climate change includes both global warming and its impacts on Earth's weather patterns.

Average surface air temperatures from 2011 to 2021 compared to the 1956–1976 average
Change in average surface air temperature since the industrial revolution, plus drivers for that change. Human activity has caused increased temperatures, with natural forces adding some variability.
Global surface temperature reconstruction over the last 2000 years using proxy data from tree rings, corals, and ice cores in blue. Directly observed data is in red.
Drivers of climate change from 1850–1900 to 2010–2019. There was no significant contribution from internal variability or solar and volcanic drivers.
concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black)
The Global Carbon Project shows how additions to since 1880 have been caused by different sources ramping up one after another.
The rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of Italy.
Sea ice reflects 50% to 70% of incoming solar radiation while the dark ocean surface only reflects 6%, so melting sea ice is a self-reinforcing feedback.
Projected global surface temperature changes relative to 1850–1900, based on CMIP6 multi-model mean changes.
The sixth IPCC Assessment Report projects changes in average soil moisture that can disrupt agriculture and ecosystems. A reduction in soil moisture by one standard deviation means that average soil moisture will approximately match the ninth driest year between 1850 and 1900 at that location.
Historical sea level reconstruction and projections up to 2100 published in 2017 by the U.S. Global Change Research Program
The IPCC Sixth Assessment Report (2021) projects that extreme weather will be progressively more common as the Earth warms.
Scenarios of global greenhouse gas emissions. If all countries achieve their current Paris Agreement pledges, average warming by 2100 would still significantly exceed the maximum 2 °C target set by the Agreement.
Coal, oil, and natural gas remain the primary global energy sources even as renewables have begun rapidly increasing.
Economic sectors with more greenhouse gas contributions have a greater stake in climate change policies.
Most emissions have been absorbed by carbon sinks, including plant growth, soil uptake, and ocean uptake (2020 Global Carbon Budget).
Since 2000, rising emissions in China and the rest of world have surpassed the output of the United States and Europe.
Per person, the United States generates at a far faster rate than other primary regions.
Academic studies of scientific consensus reflect that the level of consensus correlates with expertise in climate science.
Data has been cherry picked from short periods to falsely assert that global temperatures are not rising. Blue trendlines show short periods that mask longer-term warming trends (red trendlines). Blue dots show the so-called global warming hiatus.
The 2017 People's Climate March took place in hundreds of locations. Shown: the Washington, D.C. march, protesting policies of then-U.S. President Trump.
Tyndall's ratio spectrophotometer (drawing from 1861) measured how much infrared radiation was absorbed and emitted by various gases filling its central tube.
alt=Underwater photograph of branching coral that is bleached white|Ecological collapse. Bleaching has damaged the Great Barrier Reef and threatens reefs worldwide.<ref>{{Cite web|url=https://sos.noaa.gov/datasets/coral-reef-risk-outlook/|title=Coral Reef Risk Outlook|access-date=4 April 2020|publisher=National Oceanic and Atmospheric Administration|quote=At present, local human activities, coupled with past thermal stress, threaten an estimated 75 percent of the world's reefs. By 2030, estimates predict more than 90% of the world's reefs will be threatened by local human activities, warming, and acidification, with nearly 60% facing high, very high, or critical threat levels.}}</ref>
alt=Photograph of evening in a valley settlement. The skyline in the hills beyond is lit up red from the fires.|Extreme weather. Drought and high temperatures worsened the 2020 bushfires in Australia.<ref>{{harvnb|Carbon Brief, 7 January|2020}}.</ref>
alt=The green landscape is interrupted by a huge muddy scar where the ground has subsided.|Arctic warming. Permafrost thaws undermine infrastructure and release methane, a greenhouse gas.
alt=An emaciated polar bear stands atop the remains of a melting ice floe.|Habitat destruction. Many arctic animals rely on sea ice, which has been disappearing in a warming Arctic.<ref>{{harvnb|IPCC AR5 WG2 Ch28|2014|p=1596|ps=: "Within 50 to 70 years, loss of hunting habitats may lead to elimination of polar bears from seasonally ice-covered areas, where two-thirds of their world population currently live."}}</ref>
alt=Photograph of a large area of forest. The green trees are interspersed with large patches of damaged or dead trees turning purple-brown and light red.|Pest propagation. Mild winters allow more pine beetles to survive to kill large swaths of forest.<ref>{{Cite web|url=https://www.nps.gov/romo/learn/nature/climatechange.htm|title=What a changing climate means for Rocky Mountain National Park|publisher=National Park Service|access-date=9 April 2020}}</ref>
Environmental migration. Sparser rainfall leads to desertification that harms agriculture and can displace populations. Shown: Telly, Mali (2008).<ref>{{harvnb|Serdeczny|Adams|Baarsch|Coumou|2016}}.</ref>
Agricultural changes. Droughts, rising temperatures, and extreme weather negatively impact agriculture. Shown: Texas, US (2013).<ref>{{harvnb|IPCC SRCCL Ch5|2019|pp=439, 464}}.</ref>
Tidal flooding. Sea-level rise increases flooding in low-lying coastal regions. Shown: Venice, Italy (2004).<ref name="NOAAnuisance">{{cite web|url=http://oceanservice.noaa.gov/facts/nuisance-flooding.html |title=What is nuisance flooding? |author=National Oceanic and Atmospheric Administration |access-date=April 8, 2020}}</ref>
Storm intensification. Bangladesh after Cyclone Sidr (2007) is an example of catastrophic flooding from increased rainfall.<ref>{{harvnb|Kabir|Khan|Ball|Caldwell|2016}}.</ref>
Heat wave intensification. Events like the June 2019 European heat wave are becoming more common.<ref>{{harvnb|Van Oldenborgh|Philip|Kew|Vautard|2019}}.</ref>

These include sea level rise, and warmer, more acidic oceans.

Coral

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Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria.

Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria.

A coral outcrop on the Great Barrier Reef, Australia
its body parts
Montastraea cavernosa polyps with tentacles extended
Discharge mechanism of a stinging cell (nematocyst)
Life cycles of broadcasters and brooders
A male great star coral, Montastraea cavernosa, releasing sperm into the water.
Generalized life cycle of corals via sexual reproduction: Colonies release gametes in clusters (1) which float to the surface (2) then disperse and fertilize eggs (3). Embryos become planulae (4) and can settle onto a surface (5). They then metamorphose into a juvenile polyp (6) which then matures and reproduces asexually to form a colony (7, 8).
Basal plates (calices) of Orbicella annularis showing multiplication by budding (small central plate) and division (large double plate)
Phylogenetic tree representing bacterial Operational taxonomic units (OTUs) from clone libraries and next-generation sequencing. OTUs from next-generation sequencing are displayed if the OTU contained more than two sequences in the unrarefied OTU table (3626 OTUs).
Stable microbes may be introduced to the holobiont through horizontal or vertical transmission and persist in ecological niches within the coral polyp where growth (or immigration) rates balance removal pressures from biophysical processes and immune or ecological interactions. Transient microbes enter the holobiont from environmental sources (e.g., seawater, prey items, or suspension feeding) and removal rates exceed growth/immigration rates such that a dynamic and high diversity microbiota results. Transient and stable populations compete for resources including nutrients, light and space and the outcome of resource-based competition (bottom-up control) ultimately determines population growth rate and thus ability to persist when subject to removal. Whether a population is categorized as stable or transient may depend on the timeframe considered. AMP = antimicrobial peptides, ROS = reactive oxygen species
Locations of coral reefs around the world
Staghorn coral (Acropora cervicornis) is an important hermatypic coral from the Caribbean
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A healthy coral reef has a striking level of biodiversity in many forms of marine life.
6-strand necklace, Navajo (Native American), ca. 1920s, Brooklyn Museum
Depiction of coral in the Juliana Anicia Codex, a 6th-century copy of Dioscorides' De Materia Medica. The facing page states that coral can be used to treat ulcers.
Global sea surface temperature (SST)
Porites lutea
This dragon-eye zoanthid is a popular source of color in reef tanks.
Tabulate coral (a syringoporid); Boone limestone (Lower Carboniferous) near Hiwasse, Arkansas, scale bar is 2.0 cm
Tabulate coral Aulopora from the Devonian period
Solitary rugose coral (Grewingkia) in three views; Ordovician, southeastern Indiana
Fungia sp. skeleton
Polyps of Eusmilia fastigiata
Pillar coral, Dendrogyra cylindricus
Brain coral, Diploria labyrinthiformis
Brain coral spawning
Brain coral releasing eggs
Fringing coral reef off the coast of Eilat, Israel.
Corals, Tis Beach, Chabahar, Iran
Corals, Tis Beach, Chabahar, Iran

Ocean acidification (rising pH levels in the oceans) is threatening the continued species growth and differentiation of corals.

World map of the five-ocean model with approximate boundaries

Ocean

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Body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water.

Body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water.

World map of the five-ocean model with approximate boundaries
The Atlantic, one component of the system, makes up 23% of the "global ocean".
Surface view of the Atlantic Ocean
World distribution of mid-oceanic ridges; USGS
Map of large underwater features (1995, NOAA)
Ocean chlorophyll concentration is a proxy for phytoplankton biomass. In this map, blue colors represent lower chlorophyll and reds represent higher chlorophyll. Satellite-measured chlorophyll is estimated based on ocean color by how green the color of the water appears from space.
The major oceanic zones, based on depth and biophysical conditions
Ocean surface currents
A map of the global thermohaline circulation; blue represents deep-water currents, whereas red represents surface currents.
Map of the Gulf Stream, a major ocean current that transports heat from the equator to northern latitudes and moderates the climate of Europe.
High tide and low tide in the Bay of Fundy, Canada.
The ocean is a major driver of Earth's water cycle.
Annual mean sea surface salinity in practical salinity units (psu) from the World Ocean Atlas.
Sea surface oxygen concentration in moles per cubic meter from the World Ocean Atlas.
Diagram of the ocean carbon cycle showing the relative size of stocks (storage) and fluxes.
Residence time of elements in the ocean depends on supply by processes like rock weathering and rivers vs. removal by processes like evaporation and sedimentation.
400px

The increasing concentration of carbon dioxide in the atmosphere due to fossil fuel combustion leads to higher concentrations in ocean water, resulting in ocean acidification.

Permian–Triassic boundary at Frazer Beach in New South Wales, with the End Permian extinction event located just above the coal layer

Permian–Triassic extinction event

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The Permian–Triassic (P–T, P–Tr) extinction event, also known as the End-Permian Extinction and colloquially as the Great Dying, formed the boundary between the Permian and Triassic geologic periods, as well as between the Paleozoic and Mesozoic eras, approximately 251.9 million years ago.

The Permian–Triassic (P–T, P–Tr) extinction event, also known as the End-Permian Extinction and colloquially as the Great Dying, formed the boundary between the Permian and Triassic geologic periods, as well as between the Paleozoic and Mesozoic eras, approximately 251.9 million years ago.

Permian–Triassic boundary at Frazer Beach in New South Wales, with the End Permian extinction event located just above the coal layer
Shell bed with the bivalve Claraia clarai, a common early Triassic disaster taxon.
Sessile filter feeders like this Carboniferous crinoid, the mushroom crinoid (Agaricocrinus americanus), were significantly less abundant after the P–Tr extinction.
Lystrosaurus was by far the most abundant early Triassic land vertebrate.
Map of Pangaea showing where today's continents were at the Permian–Triassic boundary

The scientific consensus is that the causes of extinction were elevated temperatures and in the marine realm widespread oceanic anoxia and ocean acidification due to the large amounts of carbon dioxide that were emitted by the eruption of the Siberian Traps.

Since oil fields are located only at certain places on earth, only some countries are oil-independent; the other countries depend on the oil-production capacities of these countries

Fossil fuel

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Hydrocarbon-containing material formed naturally in the earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel.

Hydrocarbon-containing material formed naturally in the earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel.

Since oil fields are located only at certain places on earth, only some countries are oil-independent; the other countries depend on the oil-production capacities of these countries
A petrochemical refinery in Grangemouth, Scotland, UK
An oil well in the Gulf of Mexico
The Global Carbon Project shows how additions to since 1880 have been caused by different sources ramping up one after another.
Global surface temperature reconstruction over the last 2000 years using proxy data from tree rings, corals, and ice cores in blue. Directly observational data is in red, with all data showing a 5 year moving average.
In 2020, renewables overtook fossil fuels as the European Union's main source of electricity for the first time.

Although methane leaks are significant, the burning of fossil fuels is the main source of greenhouse gas emissions causing global warming and ocean acidification.

Formation of an atoll according to Charles Darwin

Coral reef

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Underwater ecosystem characterized by reef-building corals.

Underwater ecosystem characterized by reef-building corals.

Formation of an atoll according to Charles Darwin
Fringing reef
Fringing reef at Eilat at the southern tip of Israel
Barrier reef
Platform reef
A small atoll in the Maldives
Inhabited cay in the Maldives
The three major zones of a coral reef: the fore reef, reef crest, and the back reef
Water in the reef surface zone is often agitated. This diagram represents a reef on a continental shelf. The water waves at the left travel over the off-reef floor until they encounter the reef slope or fore reef. Then the waves pass over the shallow reef crest. When a wave enters shallow water it shoals, that is, it slows down and the wave height increases.
Locations of coral reefs
Boundary for 20 °C isotherms. Most corals live within this boundary. Note the cooler waters caused by upwelling on the southwest coast of Africa and off the coast of Peru.
This map shows areas of upwelling in red. Coral reefs are not found in coastal areas where colder and nutrient-rich upwellings occur.
Diagram of a coral polyp anatomy
Zooxanthellae, the microscopic algae that lives inside coral, gives it colour and provides it with food through photosynthesis
Close up of polyps arrayed on a coral, waving their tentacles. There can be thousands of polyps on a single coral branch.
Corals are animals and not plants. They can appear like plants because they are sessile and take root on the ocean floor. But unlike plants, corals do not make their own food.
Corraline algae Lithothamnion sp.
Deep-water cloud sponge
Eastern oysters (Crassostrea virginica)
The colour of corals depends on the combination of brown shades provided by their zooxanthellae and pigmented proteins (reds, blues, greens, etc.) produced by the corals themselves.
Most coral polyps are nocturnal feeders. Here, in the dark, polyps have extended their tentacles to feed on zooplankton.
Island with fringing reef off Yap, Micronesia
A major coral bleaching event took place on this part of the Great Barrier Reef in Australia
Coral trees cultivating juvenile corals. Corals can be out-planted onto reefs, sold for profit, or other purposes.
Coral fragments growing on nontoxic concrete
Deep sea cora ls at the Wagner Seamount. These corals are well adapted to deep water conditions where substrates are plentiful.
Coral in preparation of being relocated
Students from Nā Pua No‘eau remove invasive algae from Kāne‘ohe Bay. Programs could be created to remove algae from Caribbean reefs
Ancient coral reefs
Darwin's theory starts with a volcanic island which becomes extinct
As the island and ocean floor subside, coral growth builds a fringing reef, often including a shallow lagoon between the land and the main reef.
As the subsidence continues, the fringing reef becomes a larger barrier reef further from the shore with a bigger and deeper lagoon inside.
Ultimately, the island sinks below the sea, and the barrier reef becomes an atoll enclosing an open lagoon.
Fluorescent coral<ref>{{cite web |url=http://photography.nationalgeographic.com/wallpaper/photography/photos/coral-kingdoms/fluorescent-coral-laman/ |title=Fluorescent coral |publisher=National Geographic Society |department=photography |series=Coral kingdoms}}</ref>
Brain coral
Staghorn coral
Spiral wire coral
Pillar coral
Mushroom coral
Maze coral
Black coral
Coralline algae
thumb|Elkhorn coral
Schooling reef fish
Caribbean reef squid
Banded coral shrimp
Whitetip reef shark
Green turtle
Giant clam
Soft coral, cup coral, sponges and ascidians
Banded sea krait
The shell of Latiaxis wormaldi, a coral snail

They are under threat from excess nutrients (nitrogen and phosphorus), rising ocean heat content and acidification, overfishing (e.g., from blast fishing, cyanide fishing, spearfishing on scuba), sunscreen use, and harmful land-use practices, including runoff and seeps (e.g., from injection wells and cesspools).

Discoscaphites iris ammonite from the Owl Creek Formation (Upper Cretaceous), Owl Creek, Ripley, Mississippi

Cretaceous–Paleogene extinction event

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Sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago.

Sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago.

Discoscaphites iris ammonite from the Owl Creek Formation (Upper Cretaceous), Owl Creek, Ripley, Mississippi
Rudist bivalves from the Late Cretaceous of the Omani Mountains, United Arab Emirates. Scale bar is 10 mm.
Kronosaurus Hunt, a rendering by Dmitry Bogdanov in 2008. Large marine reptiles, including plesiosaurians such as these, became extinct at the end of the Cretaceous.
Tyrannosaurus was among the dinosaurs living on Earth before the extinction.
Hell Creek Formation
The K–Pg boundary exposure in Trinidad Lake State Park, in the Raton Basin of Colorado, shows an abrupt change from dark- to light-colored rock.
Radar topography reveals the 180 km-wide ring of the Chicxulub crater.
Artistic impression of the asteroid slamming into tropical, shallow seas of the sulfur-rich Yucatán Peninsula in what is today Southeast Mexico. The aftermath of this immense asteroid collision, which occurred approximately 66 million years ago, is believed to have caused the mass extinction of dinosaurs and many other species on Earth. The impact spewed hundreds of billions of tons of sulfur into the atmosphere, producing a worldwide blackout and freezing temperatures which persisted for at least a decade.
The river bed at the Moody Creek Mine, 7 Mile Creek / Waimatuku, Dunollie, New Zealand contains evidence of a devastating event on terrestrial plant communities at the Cretaceous–Paleogene boundary, confirming the severity and global nature of the event.
An artist's rendering of Thescelosaurus shortly after the K–Pg mass extinction. It survived by burrowing, but would soon die of starvation.

In October 2019, researchers reported that the event rapidly acidified the oceans, producing ecological collapse and, in this way as well, produced long-lasting effects on the climate, and accordingly was a key reason for the mass extinction at the end of the Cretaceous.

Crystal structure of calcite

Calcium carbonate

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Chemical compound with the formula CaCO3.

Chemical compound with the formula CaCO3.

Crystal structure of calcite
Calcite is the most stable polymorph of calcium carbonate. It is transparent to opaque. A transparent variety called Iceland spar (shown here) was used to create polarized light in the 19th century.
Calcium carbonate chunks from clamshell
Surface precipitation of CaCO3 as tufa in Rubaksa, Ethiopia
Tufa at Huanglong, Sichuan
500-milligram calcium supplements made from calcium carbonate
Travertine calcium carbonate deposits from a hot spring
Electron micrograph of needle-like calcium carbonate crystals formed as limescale in a kettle
Around 2 g of calcium-48 carbonate

The calcification processes are changed by ocean acidification.