Author: Derek Yang
Editors: Ken Saito, Elizabeth Li
Artist: Jenny Luo
Most people assume that most of our oxygen comes from trees and plants on the surface through photosynthesis. However, about fifty percent of our oxygen is produced by oceanic plankton. This underscores the importance of chemical oceanography, more commonly known as marine chemistry, in advancing our knowledge of the inner workings of marine ecosystems. More specifically, chemical oceanography studies the distribution and reactivity of chemical components within the ocean and at its boundaries. The field focuses on the various reactions and pathways that occur, shaping marine ecosystems.
Chemical oceanographers integrate concepts from chemistry, biology, geology, and physics to address many real-world issues such as climate change. Much research has been conducted to quantify the amount of carbon dioxide the ocean absorbs. Carbon dioxide is transported to the bottom of the sea through two “pumps,” called the physical and biological pumps. The physical pump is when carbon dioxide gas dissolves into the seawater, usually at low temperatures and high latitudes, which then gets carried down to the ocean floor by currents. The biological pump is when carbon dioxide gas is absorbed by phytoplankton in photosynthesis, where it’s then transferred to zooplankton when they consume phytoplankton. Carbon dioxide then travels to the bottom of the ocean, from the feces of zooplankton or their remains after they have died, where it is deposited in the ocean floor sediments and sequestered for an extremely long period. This carbon sequestration effectively reduces the concentration of greenhouse gasses in the global environment.
To understand the scale of this sequestration, it is important to know that the ocean absorbs around one-third of global carbon dioxide emissions every year. The physical pump is responsible for most of this sequestration, as it carries most of the dissolved carbon dioxide in the surface waters down to the deep sea for sequestration. The biological pump is smaller in scale and its impact varies, as it is directly correlated to the abundance of certain planktonic species. A low abundance of planktonic species would result in the biological pump transporting less carbon dioxide and vice versa.
Building on this carbon sequestration process, chemical oceanography also studies the effect of ocean acidification on marine organisms. Absorbing more carbon dioxide causes a chemical reaction in the seawater that causes its pH to drop, thus producing more acidic seawater. Moreover, human activities such as burning fossil fuels and oil spills are other major contributors to ocean acidification. This increased level of acidity can have detrimental effects on marine ecosystems and their organisms. Some dissolved carbon dioxide will react with water to form carbonic acid, decreasing the amount of available carbonate ions. Many shell organisms such as clams or oysters require the carbonate ion for calcification to build and maintain their shells. At high acidity levels, these shell organisms struggle to build strong, healthy shells; at peak acidity levels, the exoskeletons of these organisms can completely dissolve.
In contrast, some species, such as blue crabs, lobsters, and shrimps, grow stronger shells at higher acidity levels, making them more resistant to predators. However, this also leads to some adverse effects; overpopulation of certain species becomes a greater risk, which could throw the food chain off balance. Ocean acidification also affects coral reefs, which need carbonate ions to produce calcium carbonate for reef formation. With higher acidity levels, there is a decreased amount of carbonate ions, hindering the formation and maintenance of these coral reefs. Scientists predict that under these conditions, most coral reefs will be wiped out soon, leading to further imbalance in the marine environments.
A specific example of the value of chemical oceanography was in predicting and mitigating harmful algal blooms (HABs). HABs are becoming increasingly prominent because of nutrient enrichment from agricultural practices and climate change. To study them, chemical oceanographers monitored algal concentrations in bodies of water and analyzed their effects on organism health, and water quality. Their findings raised awareness of the dangers of HABs on both human and marine organism health which led to implementing numerous policies and methods to reduce agricultural runoff and develop wastewater treatments.
Given this information, chemical oceanography is vital in understanding and addressing environmental phenomena such as carbon dioxide sequestration and ocean acidification. By studying the movement of chemical components like carbon dioxide through the ocean and the chemical consequences that result in increased acidity levels, chemical oceanography provides insight into intricate interactions between elements of the marine environment and their surrounding ecosystems. Chemical oceanography is an important field of study to society that could further advance ecological conservation efforts.
Citations:
Boyle, Edward A. “Introduction: Chemical Oceanography - Chemical Reviews...
Pubs.Acs.Org/Doi/Abs/10.1021/Cr0502596.” Chemical Reviews, ACS Publications, 30 Jan. 2007, pubs.acs.org/doi/abs/10.1021/cr0502596.
“Chemical Oceanography - MIT-WHOI Joint Program.” MIT, MIT-WHOI Joint Program,
Lortie, Robert. “Longdom Publishing SL: Open Access Journals.” Longdom, Longdom
Publishing S.L, 9 June 2023, www.longdom.org/open-access/marine-chemistry-
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