Ocean Acidification

What is ocean acidification?[edit | edit source]

Since the Industrial revolution, the concentration of carbon dioxide (CO2) in the atmosphere has increased due to the burning of fossil fuels such as coal, gas, oil and other drivers of greenhouse gas emissions, including deforestation.[1] The ocean absorbs more than 25% of all emissions from the atmosphere each year.[2] The absorbed carbon dioxide dissolves in the sea water and forms carbonic acid. Carbonic acid decreases the ocean’s pH levels. The decrease in ocean pH over time is known as ocean acidification and is part of the three main factors that affect marine ecosystems: heat, acidity, and oxygen loss.[3]

The pH scale ranges from 0 to 14 with a 7 being seen as a neutral pH. Any value that is higher than 7 is considered alkaline (basic) with any value below 7 being considered acidic. The pH of water relates to the hydrogen ion concentration within the water at any given point. Over the last two centuries, the pH of the ocean’s surface water has fallen with 0.1 pH units. At a glance this does not seem like much, however, it amounts to a rather significant 30% increase in ocean acidity.[4]

How ocean acidification is affecting life below water[edit | edit source]

The impact of ocean acidification can be seen in organisms that require calcium carbonate from seawater, like oysters and coral at this point. With increasing acidity, their shells and skeletons cannot form as well and may eventually begin to dissolve. In an experiment with pteropods, also known as sea butterflies, scientists used predicted pH levels for the year 2100 to determine possible effects on these creatures and found that the shells of pteropods slowly dissolved over a 45-day period at corresponding pH levels. Researchers also discovered that pteropods have already endured significant shell dissolution in the Southern Ocean around Antarctica, thus identifying this as a present, rather than a future effect of ocean acidification.[5]

Ocean acidification is affecting life under water in many other ways, like disabling certain fish species, e.g., clownfish, to detect predators in the way they normally would. According to the National Marine Sanctuaries, the Zoea and Megalopa larvae stages of the Dungeness crab are also affected by the rise in pH. Exposure to lower pH levels in seawater result in decreased larval development rates and later survival, which, in turn, impacts their prey species, and so on. [6]

Analogues in the human body: pH-levels and basic biological processes[edit | edit source]

Physiotherapists and other health professionals might understand the importance of pH balance by thinking of analogues in the human body.

As humans our bodies are largely composed of water, our pH, or acid-base balance is critically important to our daily lives and health. The normal pH range for humans is between 7.35 and 7.45.[7] This range is crucial for basic biological processes, most importantly the oxygenation of blood (the body’s ability to filter oxygen for absorption into tissues for function). There are four main deviations from the baseline, metabolic alkalosis/acidosis and respiratory alkalosis/acidosis.[8]

A normal pH means that there is appropriate oxygen delivery to our bodily tissues, that biochemical processes remain constant, and essential protein structures like those responsible for muscle contraction will stay intact. Muscle fibers are bundled together with many myofibrils making up each muscle. Striated muscles have transverse lines that form as a result of protein arrangements. If these protein structures are affected, muscle contractions will also be affected.[9]

The two important biochemical systems that are affected by changes in pH levels are the renal and pulmonary systems. Carbon dioxide forms carbonic acid in the body when combined with water. To this, our bodies respond by increasing or decreasing the amount of carbon dioxide expired in each breath. The renal system responds by re-absorbing more or less bicarbonate, the remaining bicarbonate being excreted in urine.[3] Metabolic and respiratory acidosis can result in altered breathing, confusion, fatigue, headaches, drowsiness, decreased appetite, jaundice, chronic lung disease, neuromuscular disorders and altered heart rate. Chronic conditions such as diabetes, congenital heart defects and asthma may also be exacerbated.[10];[11]

Whether inside our body, or in other ecosystems like the ocean, pH balance is of fundamental importance to biological life and health on our planet. In addition, the ocean and our bodies are in constant interaction with each other in many different ways.

Ocean acidification and implication for human societies, life and health[edit | edit source]

Billions of people rely on the ocean for food and income. Apart from losing this source of income through lower abundance and lower diversity of life under water, humans will likely also be impacted by a loss of essential nutrients. If, for example, marine species contain less calcium as an indirect result of ocean acidification. [12] Humans require calcium for healthy bone and teeth development, but also for blood vessel contraction/expansion, muscle contraction, neural messaging, and hormonal secretion by certain glands.[13] If there is a significant rise in ocean acidification, the calcium absorbed through fish (like salmon or sardines, who store calcium in their soft bones)[14] will decline and we will likely see significant side-effects.

Researchers have discovered that salt intrusion is rapidly occurring in seaside communities. Salt intrusion occurs as a result of excessive groundwater pumping, a rising sea level and many other factors that causes seawater to enter fresh groundwater supplies. As we cannot use seawater for irrigation or consumption this is a growing concern.[15] If this should continue to occur, the rate of ocean acidification will have a direct impact on our fresh water consumption and the irrigation of our crops, especially in coastal communities. Due to the effects predicted for the ecosystems surrounding these ground water catchment areas, we can also expect to see changes in the health of the communities in the surrounding area.

Ocean acidification, sustainable healthcare and environmental physiotherapy[edit | edit source]

The direct implications of ocean acidification on physiotherapy are not entirely clear yet. However, as physiotherapy grows in the field of planetary health and environmental physiotherapy, it becomes critically important that we understand the increasing environmental challenges we are facing today. Ocean acidification forms part of this bigger environmental health picture.

Protecting life on the surface of and deeper under water, has been identified as a central requirement for sustainable futures for life on earth. To combat these affects the United Nations have set up the Sustainable Development Goals (SDGs), with the aim to address concerns regarding the conservation and sustainable use of oceans, seas and marine resources for sustainable development. SDG 14 is specifically focused on Life below water, and minimizing ocean acidification one of its key objectives. Suggestions to aid in reducing environmental degradation of the ocean include participating in ocean clean-up projects, buying local and certified fish and staying informed on the matter.[16] Future research will need to look at both direct and indirect effects of ocean acidification and ecosystems change on human and the implications this will have on the provision of physiotherapy services.

Related articles[edit | edit source]

An Introduction to Environmental Physiotherapy

Biodiversity and Physiotherapy

Sustainable Healthcare and Environmental Physiotherapy

Arterial Blood Gases

External Resources[edit | edit source]

  1. NOAA. (2020, April 1). Ocean Acidification. Retrieved from NOAA: https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-acidification
  2. IUCN. (2011, June 29). Ocean Acidification. Retrieved from IUCN: https://www.iucn.org/search?key=ocean%20acidification
  3. Hopkins, E., Sanvictores, T., & Sharma, S. (2021, September 14). Physiology, Acid Base Balance. Retrieved from National Library of Medicine: https://www.ncbi.nlm.nih.gov/books/NBK507807/
  4. Unilever. (2022, 07 06). Proteins in structures. Retrieved from School Science: http://resources.schoolscience.co.uk/unilever/16-18/proteins/Protch5pg3.html
  5. Inc., A. (2022, 01 06). National Library of Medicine. Retrieved from MedlinePlus: https://medlineplus.gov/ency/article/001181.htm
  6. Resources, W. (2019, March 2). Saltwater Intrusion. Retrieved from USGS : https://www.usgs.gov/mission-areas/water-resources/science/saltwater-intrusion#overview
  7. Nations, U. (2022, 07 10). Global Goals. Retrieved from 14 Life Below Water: https://www.globalgoals.org/goals/14-life-below-water/