Estuarine acidification
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Estuarine acidification happens when the
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.
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
As the pH of marine systems decreases, it causes
Research
Estuarine acidification is being studied to understand the biological, chemical, and physical factors that affect pH in estuaries.[14]
References
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- ISBN 9781468474268.
- ^ S2CID 31054160.
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- ISSN 1467-8470.
- S2CID 22245513.
- ^ "PH of coastal waterways".
- ^ NOAA "Estuary Education" Archived 2013-10-29 at the Wayback Machine
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- ISBN 978-0-309-04826-2.
- S2CID 35487689.
- S2CID 4306199.
- PMID 21906222.
- .