Ocean Acidification: Photosynthesis in the seas

By: Charlotte Shum

For years due to technologies rapidly evolving and the increasing use of thermal electricity, the Earth’s environment began to slowly—then quickly—deteriorate. This change went unbelieved, deemed unimportant for many years, until 1972 when it was officially mentioned at a UN environment conference (BBC, 2013). This change—called global warming—was really the heating of the Earth’s atmosphere due to the gases thermal power stations produced; which caused an abundance of other issues such as ocean acidification. 

Ocean acidification is the decrease of pH in the Earth’s oceans, harming marine environments and species. It is extremely important that this issue is stopped, or else the ocean—70.9% of the Earth—could be drastically changed (National Centre For Environmental Protection, 2010).

The ocean naturally absorbs carbon dioxide and other greenhouse gases in the atmosphere and in a way, stores them. But because of global warming increasing the level of carbon dioxide at extreme rates, the ocean’s pH level has been unnaturally decreasing from an alkaline to becoming more and more acidic. Currently, the ocean’s average pH level is approximately 8.1, a decrease from the pre-industrial revolution average of 8.2. Despite the seemingly small decrease, this is a huge change. To put the pH level’s difference in other words, the ocean’s acidity has increased by 30% since times prior to the Industrial Revolution (Jones, 2016).

Ocean acidification needs a direct solution; the solution being the plantation and regrowth of kelp and seagrass. Growing sea plants can reduce acidity in the ocean and naturally integrate into marine environments. Sea plants are capable of taking in carbon dioxide through photosynthesis, causing the surrounding ecosystem’s acidity to decrease (Jones, 2016). This solution can protect other organisms in a direct and fast-acting way. 

While kelp and seagrasses may seem like a small-scale solution in the big picture, this solution is much lower in risk than similarly direct solutions such as iron fertilisation which could impact existing food webs, or place particles in the upper atmosphere to deflect gases which does not particularly decrease already existing gases (Smithsonian, n.d). 

Sea plants are living organisms that naturally inhabit the ocean. They are a self-maintaining solution, capable of reproduction through varying means (Britannica, n.d). In addition to helping reduce acidity, reintegrating seagrasses and kelp into the ocean would serve as a form of restoring the ocean’s ecosystems, as seagrasses have reduced production by 29% since the 20th century (Kelly et al, 2019).

Despite the plantation of kelp and seagrasses not yet being done on a large scale basis, there is clear evidence of the impact of seagrass meadows specifically on the California coast. During a study spanning over six years, it was found that local ocean acidity could be reduced by up to 30% due to seagrass meadows (Kerlin, 2021). The brief reduction of acidity occurred at a 65% rate in areas across the California Coast, and it was also shown that the effect of these seagrass meadows extended for days and weeks on end, even with the lack of photosynthesis. 

The growth of seagrasses and kelp has been proven successful in buffering ocean acidification, and the implications of that are extensive. In terms of social factors, recreational diving could be immensely better, as the coral would be able to regrow instead of dissolving due to ocean acidification. According to Dr Sutton (2010), while there may always be diving spots in marine ecosystems, the ability to directly view the coral reefs is decreasing, harming not only the environment but also recreational diving businesses and opportunities for future generations to see such organisms. By buffering ocean acidification using kelps and seagrasses, not only will the pH level increase, but underwater ecosystems will be enhanced with the regrowth of previously lost plants.  

However, because of a lack of understanding of seagrass seed growth, the process of seed germination and growth takes a while to be successful. This causes seagrass restoration to become fairly costly, with the average cost of seagrass replanation estimated at around $106,782 USD—or simply $833,262.70HKD (Parry, 2010). For instance, a study in New Zealand has mentioned that the flowering of seagrass was more common than expected and cited the rarity of seagrass seeds as the reason (Clark & Berthelsen, 2021).

The impact of using restoring sea plants will be considerably weakened by environmental and economic factors and seagrasses will not be used extensively, but despite that, seagrass can still reduce acidity in local regions. 

In conclusion, the restoration of sea plants will be one of the most low-risk and sustainable solutions to the acidifying ocean. However, it may not be effectively used for the foreseeable future as more research is needed on the growth of seagrass. In spite of this, sea plants have already managed to efficiently reduce acidity regionally.

Rationale:

An investigative piece on one of the environmental issues brought on by climate change, aiming to build a basic understanding of ocean acidification within the reader.