Ocean acidification is one of the most crucial environmental issues affecting the earth today. Ocean acidification is caused by the decrease of PH levels in the ocean through the continuous increase of CO2 in the atmosphere (Bates, 2009). 30-40% of CO2 pollution is absorbed by oceans, rivers and lakes, making the ocean the largest carbon sink in the world (Poore, 2013). Significant amounts of marine organisms, ranging from phytoplankton to fish, are sensitive to shifts in carbonate chemistry, and their responses towards these changes could lead to drastic ecological shifts in marine ecosystems (Kroeker, 2010).
Sea shells are greatly affected by acidified waters, the increased acidic levels due to decreased ph levels cause shells to become eroded, this is due to the fact that shells consist of carbonate ions (Hoegh-Guldberg, 2007). When CO2 reacts with seawater, it releases extra hydrogen, making the water more acidic, these hydrogen ions compete with shells for carbonate causing their skeletal bodies to become significantly weaker (Hoegh-Guldberg, 2007). If the acidity of the oceans continues to rise, the shells of these organisms will dissolve completely.
Coral is another species heavily impacted by acidification, they are part plant, part animal, and part rock animal, living in symbiosis, the rock portion of coral is made of limestone and deposited in layers over time (Ries, 2009). The animal portion of coral has stinging cells similar to jellyfish, they have microscopic algae which harvests energy from the sun and creates food (Ries, 2009). This algae is also what gives colour to the coral and is essential to the corals survival, due to coral bleaching and rising water temperatures however, this algae is expelled and its limestone skeleton is revealed, causing it to die (Ries, 2009). Once dead, the coral cannot regenerate even if water temperatures decrease. The increasing death of coral reefs is detrimental to ocean species and ecosystems as coral is the basis of ocean food chains, without it entire ecosystems would be affected (Hoegh-Guldberg, 2007).
Global temperatures are projected to increase rapidly to 1.8°C above today's average temperature (Poore, 2013). During the 20th century, increasing carbon dioxide levels has already increased the oceans' global average temperature by 0.74°C, sea level by 17 cm, as well as depleted seawater carbonate concentrations by ∼30 μmol kg–1 seawater and acidity by 0.1 pH unit (Poore, 2013). Approximately 25% of the CO2 emitted from all anthropogenic sources currently enters the ocean, once absorbed, it reacts with water to produce carbonic acid and thus acidification. (citations 4, reword) The issue of ocean acidification is crucial to the survival of the ocean, the earth's ecosystems, and our own and therefore must be taken seriously, its destructive effects will only worsen over time.
Annotated Bibliography
Bates, N. et al. (2009). The Arctic Ocean marine carbon cycle: evaluation of
air-sea CO2 exchanges, ocean acidification impacts and potential Feedbacks. Biogeosciences. Retrieved from https://www.biogeosciences.net/6/2433/2009/
bg-6-2433-2009.pdf
This article argues the effects of the marine carbon cycle in the arctic. Seasonal
sea-ice cover the gas exchange between the ocean and the atmosphere. The ocean takes up carbon dioxide, reducing 5-14% of the global balance of CO2 sinks and sources. Due to this, the Arctic Ocean plays a vital role in the global carbon cycle. Continuous arctic sea ice loss and increases in phytoplankton growth levels will increase the amount of carbon dioxide absorbed by the ocean's surface water, although this absorption may be slightly reduced due to ocean warming. Therefore, the Arctic Ocean's ability to absorb carbon dioxide from the atmosphere will be altered due to the environmental changes caused by climate change and will further continue the shift in physics, biogeochemistry and the ecology of the arctic ocean. In areas with shallower waters, and therefore an increased amount of surface water, melted water from sea ice, and the absorption of CO2 through gas exchange, all combine in the decrease of calcium carbonate as well as mineral saturation rates of arctic ocean water.
Hoegh-Guldberg, O. et al. (2007). Coral Reefs Under Rapid Climate Change and Ocean
Acidification. American Association for the Advancement of Science. Retrieved from http://science.sciencemag.org/content/318/5857/1737.full
This article reviews how anthropogenic climate change and continuous acidity affects coral reefs and and looks at situations of how will change over time in the next centuries. The situations provide a framework for actions that can be taken towards coral reef ecosystems and to provide thought on future management and policy obstacles for coral reef conservation. Under current and expected conditions in the 21st century, global warming and ocean acidification will reduce carbon amounts, therefore causing a steady decrease in coral species within reef systems. This will result in reduced diversity within ocean ecosystems of key species and reduced quality of water, exacerbating functional collapse in ecosystems. The article provides future scenarios for coral reef systems that foresee consequences for reef-associated fisheries, tourism, coastal protection, and human interaction. Increased management intervention and actions on global CO2 emissions are necessary to avoid the loss coral ecosystems.
Kroeker, K. et al. (2010). Meta-analysis reveals negative yet variable effects of ocean
acidification on marine organisms. Ecology Letters. Retrieved from http://online
library.wiley.com/doi/10.1111/j.1461-0248.2010.01518.x/full
This article discusses the issue of ocean acidification and its effects on many marine species living in ocean habitats the cause of serious ecological shifts. Many biological responses to ocean acidification have already been measured across the world and the effects are clearly evident, this article discusses the use of meta-analytic techniques to investigate the biological responses to ocean acidification. The research found several negative effects on survival, calcification, growth and reproduction. It also found significant variation in the sensitivity of marine organisms towards the effects of ocean acidification. Calcifying organisms largely showed stronger negative responses than non-calcifying organisms, excluding crustaceans, which calcify but did not show signs of negative affects. The responses of calcification varied greatly among organisms that use different forms of minerals of calcium carbonate. Organisms that use soluble forms of calcium carbonate are more resistant to ocean acidification than less soluble forms. The article also explains that there is fluctuations in the sensitivities of various developmental stages, but this depends on the taxonomic group. The articles proposes that the biological effects of ocean acidification are generally large and negative, although the fluctuations in sensitivity amongst organisms has important implications for ecosystem responses.
Poore, A. et al. (2013). Direct and indirect effects of ocean acidification and warming on
a marine plant–herbivore interaction. Oecologia. Retrieved from https://link.sprin
ger.com/article/10.1007/s00442-013-2683-y
This article examines both the direct and indirect effects of ocean acidification and global warming on the interactions between marine plants and organisms. The various impacts of climate change on organisms relies largely on the interactions of stressors and how these potentially affect the interactions between organisms. One of the major interactions affected is the relationship between consumers and predatory species. This change may be caused by the fluctuations in populations of either of these specie types or due to the per capita interaction strength among species. During the examination of the effects of multiple stressors on the interaction between species, the direct and interactive effects of ocean warming and the decreasing pH levels on marine herbivores were tested. It also examined if herbivores are indirectly affected by these stressors and if it affects their access to algal food. The study found, that the increased temperature of earth's waters, the decrease in pH levels, and the access to algae food supplies reduced the survival of amphipod survival and growth, especially due to increased water temperatures. These results from the article indicate that the direct effects on herbivore abundance and climatic stressors affects the strength of plant–herbivore interactions.
Ries, B. et al. (2009). Marine calcifiers exhibit mixed responses to CO2-induced ocean
acidification. GeoScienceWorld. Retrieved from https://pubs.geoscienceworld.org
/geology/article-lookup/37/12/113
This article reviews the various responses of marine calcifiers to ocean
acidification caused by ocean acidification. According to this research, human
increase of carbon dioxide levels in the atmosphere is causing the ocean to become more acidic and therefore causes the reduction of saturation by calcium carbonate. This issue is particularly problematic for species that create their shells and skeletons from calcium carbonate minerals. 60 laboratory experiments were performed investigating the effects of CO2 on calcification in 18 benthic marine organisms. The tested species were very broad in selection and included organisms which produce aragonite, low-Mg calcite, and high-Mg calcite forms of calcium carbonate. The results showed that 10 of the 18 studied species showed decreased rates of net calcification. In some species however, results showed that some species only began showing signs of net calcification under very high levels of carbon and one species expressed no effects at all. These responses demonstrate the varied ability of some organisms to regulate pH in calcification conditions, the extent to which their shell layers can be protected and their use of photosynthesis.