Estuarine acidification

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Estuarine acidification happens when the pH balance of water in coastal marine ecosystems, specifically those of estuaries, decreases. Water, generally considered neutral on the pH scale, normally perfectly balanced between alkalinity and acidity. While ocean acidification occurs due to the ongoing decrease in the pH of the Earth's oceans, caused by the absorption of carbon dioxide (CO2) from the atmosphere, [1] pH change in estuaries is more complicated than in the open ocean due to direct impacts from land run-off, human impact, and coastal current dynamics. In the ocean, wave and wind movement allows carbon dioxide (CO2) to mixes with water (H2O) forming carbonic acid (H2CO3). Through wave motion this chemical bond is mixed up, allowing for the further break of the bond, eventually becoming carbonate (CO3) which is basic and helps form shells for ocean creatures, and two hydron molecules. This creates the potential for acidic threat since hydron ions readily bond with any Lewis Structure to form an acidic bond. [2] This is referred to as an oxidation-reduction reaction.

Contents

The basic chemical equation is as follows:

CO2 + H2O H2CO3 HCO3 + H+ CO3 + 2 H+

When this pattern of absorption is transferred into an estuary, however, acidity increases simply due to relative volume. Ocean water counts for the absorption of 30-40 percent of all CO2 emitted into the atmosphere and yet, due to its immense volume, it remains relatively resilient. [3] Estuaries - being smaller by volume, sheltered from wave motion, and victim to human impact when in an urban setting - do not readily support the mixing of water, and thereby prevents basic breakdown. [4] When this is combined with CO2 from human impact such as car emissions or fertilizers, oxidation more readily occurs due to the overabundance of hydron ions and additional cation, increasing the rate of occurrence and duration of acidification taking place. [5] As the acidity of estuarine water levels continues to fluctuate, several species who use estuaries as spawning nurseries have seen decreases in reproduction levels. [6]

Causes of variable pH

Freshwater flow

An estuary is defined as "a water passage where the tide meets a river current". The pH of estuaries is highly variable because of freshwater flow from rivers and groundwater, as well as primary productivity (exacerbated by nutrient loading) and coastal upwelling. Fresh water from rivers typically has a lower pH than ocean water (~7 compared to ~8). Seasonal and annual changes in river flow entering an estuary can change the pH by whole units. [7]

Photosynthesis and respiration

Primary production (plant growth) changes pH on a daily, seasonal, and annual basis. During photosynthesis, carbon dioxide is removed from the water, increasing pH. Organisms release carbon dioxide during respiration. [8] This leads to a daily cycle of increased pH during daylight hours and a decrease in pH during the night, when respiration is dominant. Similarly, pH is higher during the winter when grazing is low compared to productivity. [9]

Effluent

Many estuaries experience nutrient loading from runoff containing wastewater effluent or fertilizers, natural or artificial. Increased nutrients can stimulate primary productivity and alter the balance between primary productivity and respiration. This process can change pH by whole units within the estuary. Both these processes make it difficult to measure the overall change in pH associated with increased atmospheric carbon dioxide levels. This causes a change in pH by whole units in the estuary. This makes it hard to measure the overall change in pH, as well as the increased atmospheric carbon dioxide levels. [10]

Currents

Areas with coastal upwelling such as the west coast of North America have experienced increases in acidification due to more acidic deep water upwelling into the estuary. [11] This may have a detrimental effect on the survival of calcifying organisms [12] because the organisms have a much more difficult time forming and maintaining their calcium carbonate shells. [3]

Impact on marine life

A coccolithophore with many coccoliths (plates) formed from calcium carbonate Coccolithus pelagicus.jpg
A coccolithophore with many coccoliths (plates) formed from calcium carbonate

As the pH of marine systems decreases, it causes calcium carbonate (CaCO3) to dissociate [3] to keep in chemical equilibrium. Calcium carbonate is vital to calcifying organisms such as shellfish, corals, and coccolithophores (a type of phytoplankton). Acidification also harms micro-organisms in the environment. These organisms either directly provide humans with a food source or supports an ecosystem important to humans. [13]

Research

Estuarine acidification is being studied to understand the biological, chemical, and physical factors that affect pH in estuaries. [14]

Related Research Articles

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The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Carbon is the main component of biological compounds as well as a major component of many minerals such as limestone. Along with the nitrogen cycle and the water cycle, the carbon cycle comprises a sequence of events that are key to make Earth capable of sustaining life. It describes the movement of carbon as it is recycled and reused throughout the biosphere, as well as long-term processes of carbon sequestration to and release from carbon sinks. Carbon sinks in the land and the ocean each currently take up about one-quarter of anthropogenic carbon emissions each year.

<span class="mw-page-title-main">Estuary</span> Partially enclosed coastal body of brackish water

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.

<span class="mw-page-title-main">Biological pump</span> Carbon capture process in oceans

The biological pump (or ocean carbon biological pump or marine biological carbon pump) is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments. In other words, it is a biologically mediated processes which result in the sequestering of carbon in the deep ocean away from the atmosphere and the land. The biological pump is the biological component of the "marine carbon pump" which contains both a physical and biological component. It is the part of the broader oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO3) formed into shells by certain organisms such as plankton and mollusks (carbonate pump).

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<span class="mw-page-title-main">Solubility pump</span> Physico-chemical process which transports carbon

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<span class="mw-page-title-main">Dissolved inorganic carbon</span> Sum of inorganic carbon species in a solution

Dissolved inorganic carbon (DIC) is the sum of the aqueous species of inorganic carbon in a solution. Carbon compounds can be distinguished as either organic or inorganic, and as dissolved or particulate, depending on their composition. Organic carbon forms the backbone of key component of organic compounds such as – proteins, lipids, carbohydrates, and nucleic acids.

<span class="mw-page-title-main">Ocean acidification</span> Climate change-induced decline of pH levels in the ocean

Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxide emissions from human activities which have led to atmospheric carbon dioxide (CO2) levels of more than 410 ppm (in 2020). The oceans absorb CO2 from the atmosphere. This leads to the formation of carbonic acid (H2CO3) which dissociates into a bicarbonate ion (HCO−3) and a hydrogen ion (H+). The free hydrogen ions (H+) decrease the pH of the ocean, therefore increasing acidity (this does not mean that seawater is acidic yet; it is still alkaline, with a pH higher than 8). A decrease in pH corresponds to a decrease in the concentration of carbonate ions, which are the main building block for calcium carbonate (CaCO3) shells and skeletons. Marine calcifying organisms, like mollusks, oysters and corals, are particularly affected by this as they rely on calcium carbonate to build shells and skeletons.

<span class="mw-page-title-main">Ocean deoxygenation</span> Reduction of the oxygen content of the oceans

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<span class="mw-page-title-main">Hypoxia (environmental)</span> Low oxygen conditions or levels

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<span class="mw-page-title-main">Shell growth in estuaries</span>

Shell growth in estuaries is an aspect of marine biology that has attracted a number of scientific research studies. Many groups of marine organisms produce calcified exoskeletons, commonly known as shells, hard calcium carbonate structures which the organisms rely on for various specialized structural and defensive purposes. The rate at which these shells form is greatly influenced by physical and chemical characteristics of the water in which these organisms live. Estuaries are dynamic habitats which expose their inhabitants to a wide array of rapidly changing physical conditions, exaggerating the differences in physical and chemical properties of the water.

<span class="mw-page-title-main">Freshwater acidification</span>

Freshwater acidification occurs when acidic inputs enter a body of fresh water through the weathering of rocks, invasion of acidifying gas, or by the reduction of acid anions, like sulfate and nitrate within the lake. Freshwater acidification is primarily caused by sulfur oxides (SOx) and nitrogen oxides (NOx) entering the water from atmospheric depositions and soil leaching. Carbonic acid and dissolved carbon dioxide can also enter freshwaters in a similar manner associated with runoff through carbon dioxide-rich soils. Runoff that contains these compounds may be accompanied by acidifying hydrogen ions and inorganic aluminum, which can be toxic to marine organisms. Acid rain is also a contributor to freshwater acidification. It is created when SOx and NOx react with water, oxygen, and other oxidants within the clouds.

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<span class="mw-page-title-main">Ocean acidification in the Arctic Ocean</span>

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<span class="mw-page-title-main">Human impact on marine life</span>

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<span class="mw-page-title-main">Jean-Pierre Gattuso</span> French ocean scientist (born 1958)

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<span class="mw-page-title-main">Particulate inorganic carbon</span>

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References

  1. Caldeira, Ken; Wickett, Michael E. (2003). "Oceanography: Anthropogenic carbon and ocean pH". Nature. 425 (6956): 365. Bibcode:2003Natur.425..365C. doi: 10.1038/425365a . PMID   14508477. S2CID   4417880.
  2. Weinhold, Frank; Carpenter, John E. (1988). The Structure of Small Molecules and Ions. Springer, Boston, MA. pp. 227–236. doi:10.1007/978-1-4684-7424-4_24. ISBN   9781468474268.
  3. 1 2 3 Feely, R. A.; Sabine, C. L.; Lee, K; Berelson, W; Kleypas, J; Fabry, V. J.; Millero, F. J. (2004). "Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans". Science. 305 (5682): 362–6. Bibcode:2004Sci...305..362F. doi:10.1126/science.1097329. PMID   15256664. S2CID   31054160.
  4. Feely, Richard A.; Alin, Simone R.; Newton, Jan; Sabine, Christopher L.; Warner, Mark; Devol, Allan; Krembs, Christopher; Maloy, Carol (2010-08-10). "The combined effects of ocean acidification, mixing, and respiration on pH and carbonate saturation in an urbanized estuary". Estuarine, Coastal and Shelf Science. 88 (4): 442–449. Bibcode:2010ECSS...88..442F. doi:10.1016/j.ecss.2010.05.004.
  5. Sammut, J.; Melville, M. D.; Callinan, R. B.; Fraser, G. C. (1995-04-01). "Estuarine Acidification: Impacts on Aquatic Biota of Draining Acid Sulphate Soils". Australian Geographical Studies. 33 (1): 89–100. doi:10.1111/j.1467-8470.1995.tb00687.x. ISSN   1467-8470.
  6. Urho, Lauri; Hildén, Mikael; Hudd, Richard (1990-04-01). "Fish reproduction and the impact of acidification in the Kyrönjoki River estuary in the Baltic Sea". Environmental Biology of Fishes. 27 (4): 273–283. doi:10.1007/BF00002746. ISSN   0378-1909. S2CID   22245513.
  7. "PH of coastal waterways".
  8. NOAA "Estuary Education" Archived 2013-10-29 at the Wayback Machine
  9. Feely, Richard A.; Alin, Simone R.; Newton, Jan; Sabine, Christopher L.; Warner, Mark; Devol, Allan; Krembs, Christopher; Maloy, Carol (2010). "The combined effects of ocean acidification, mixing, and respiration on pH and carbonate saturation in an urbanized estuary". Estuarine, Coastal and Shelf Science. 88 (4): 442–9. Bibcode:2010ECSS...88..442F. doi:10.1016/j.ecss.2010.05.004.
  10. Council, National Research; Studies, Division on Earth Life; Commission On Geosciences, Environment Resources; Areas, Committee on Wastewater Management for Coastal Urban (1993). A THE ROLE OF NUTRIENTS IN COASTAL WATERS | Managing Wastewater in Coastal Urban Areas | The National Academies Press. doi:10.17226/2049. ISBN   978-0-309-04826-2.
  11. Feely, R. A.; Sabine, C. L.; Hernandez-Ayon, J. M.; Ianson, D.; Hales, B. (2008). "Evidence for Upwelling of Corrosive "Acidified" Water onto the Continental Shelf". Science. 320 (5882): 1490–2. Bibcode:2008Sci...320.1490F. CiteSeerX   10.1.1.328.3181 . doi:10.1126/science.1155676. PMID   18497259. S2CID   35487689.
  12. Orr, James C.; Fabry, Victoria J.; Aumont, Olivier; Bopp, Laurent; Doney, Scott C.; Feely, Richard A.; Gnanadesikan, Anand; Gruber, Nicolas; Ishida, Akio; Joos, Fortunat; Key, Robert M.; Lindsay, Keith; Maier-Reimer, Ernst; Matear, Richard; Monfray, Patrick; Mouchet, Anne; Najjar, Raymond G.; Plattner, Gian-Kasper; Rodgers, Keith B.; Sabine, Christopher L.; Sarmiento, Jorge L.; Schlitzer, Reiner; Slater, Richard D.; Totterdell, Ian J.; Weirig, Marie-France; Yamanaka, Yasuhiro; Yool, Andrew (2005). "Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms" (PDF). Nature. 437 (7059): 681–6. Bibcode:2005Natur.437..681O. doi:10.1038/nature04095. PMID   16193043. S2CID   4306199.
  13. Witt, Verena; Wild, Christian; Anthony, Kenneth R. N.; Diaz-Pulido, Guillermo; Uthicke, Sven (2011). "Effects of ocean acidification on microbial community composition of, and oxygen fluxes through, biofilms from the Great Barrier Reef". Environmental Microbiology. 13 (11): 2976–89. doi:10.1111/j.1462-2920.2011.02571.x. PMID   21906222.
  14. Feely, Richard A.; Alin, Simone R.; Newton, Jan; Sabine, Christopher L.; Warner, Mark; Devol, Allan; Krembs, Christopher; Maloy, Carol (2010-08-10). "The combined effects of ocean acidification, mixing, and respiration on pH and carbonate saturation in an urbanized estuary". Estuarine, Coastal and Shelf Science. 88 (4): 442–449. Bibcode:2010ECSS...88..442F. doi:10.1016/j.ecss.2010.05.004.